From f16cff19af808d1f1272d8fd27be530310c605f7 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 13 Dec 2024 11:37:08 -0500
Subject: [PATCH 01/47] draft

---
 contracts/token/ERC6909/draft-ERC6909.sol | 96 +++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 contracts/token/ERC6909/draft-ERC6909.sol

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
new file mode 100644
index 00000000000..5796ebb851c
--- /dev/null
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (token/ERC6909/draft-ERC6909.sol)
+
+pragma solidity ^0.8.20;
+
+import {IERC6909} from "../../interfaces/draft-IERC6909.sol";
+import {Context} from "../../utils/Context.sol";
+import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
+
+contract ERC6909 is Context, ERC165, IERC6909 {
+    mapping(uint256 id => mapping(address account => uint256)) private _balances;
+
+    mapping(address account => mapping(address operator => bool)) private _operatorApprovals;
+
+    // Used as the URI for all token types by relying on ID substitution, e.g. https://token-cdn-domain/{id}.json
+    string private _uri;
+
+    mapping(address account => mapping(address operator => mapping(uint256 => uint256))) private _allowances;
+
+    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
+        return interfaceId == type(IERC6909).interfaceId || super.supportsInterface(interfaceId);
+    }
+
+    function balanceOf(address account, uint256 id) public view virtual override returns (uint256) {
+        return _balances[id][account];
+    }
+
+    function allowance(address owner, address spender, uint256 id) public view virtual override returns (uint256) {
+        return _allowances[owner][spender][id];
+    }
+
+    function isOperator(address owner, address operator) public view virtual override returns (bool) {
+        return _operatorApprovals[owner][operator];
+    }
+
+    function approve(address spender, uint256 id, uint256 amount) external virtual override returns (bool) {
+        _allowances[_msgSender()][spender][id] = amount;
+
+        emit Approval(_msgSender(), spender, id, amount);
+
+        return true;
+    }
+
+    function setOperator(address spender, bool approved) external virtual override returns (bool) {
+        _operatorApprovals[_msgSender()][spender] = approved;
+
+        emit OperatorSet(_msgSender(), spender, approved);
+
+        return true;
+    }
+
+    function transfer(address to, uint256 id, uint256 amount) external virtual override returns (bool) {
+        _update(_msgSender(), to, id, amount);
+
+        return true;
+    }
+
+    function transferFrom(
+        address from,
+        address to,
+        uint256 id,
+        uint256 amount
+    ) external virtual override returns (bool) {
+        address caller = _msgSender();
+        if (caller != from && !isOperator(from, caller)) {
+            if (_allowances[from][_msgSender()][id] != type(uint256).max) {
+                _allowances[from][_msgSender()][id] -= amount;
+            }
+        }
+
+        _update(from, to, id, amount);
+
+        return true;
+    }
+
+    function _update(address from, address to, uint256 id, uint256 amount) internal virtual {
+        address caller = _msgSender();
+
+        if (from != address(0)) {
+            _balances[id][from] -= amount;
+        }
+        if (to != address(0)) {
+            _balances[id][to] += amount;
+        }
+
+        emit Transfer(caller, from, to, id, amount);
+    }
+
+    function _mint(address to, uint256 id, uint256 amount) internal {
+        _update(address(0), to, id, amount);
+    }
+
+    function _burn(address from, uint256 id, uint256 amount) internal {
+        _update(from, address(0), id, amount);
+    }
+}

From 9a3ea2f89bfe9a06d72e800246d005d1fe4c8d10 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 16 Dec 2024 15:13:46 -0500
Subject: [PATCH 02/47] add extensions

---
 contracts/token/ERC6909/draft-ERC6909.sol     |  4 +--
 .../extensions/draft-ER6909TokenSupply.sol    | 25 ++++++++++++++
 .../extensions/draft-ERC6909ContentURI.sol    | 28 ++++++++++++++++
 .../extensions/draft-ERC6909Metadata.sol      | 33 +++++++++++++++++++
 4 files changed, 88 insertions(+), 2 deletions(-)
 create mode 100644 contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
 create mode 100644 contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
 create mode 100644 contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 5796ebb851c..9bcde8b82b4 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -12,8 +12,8 @@ contract ERC6909 is Context, ERC165, IERC6909 {
 
     mapping(address account => mapping(address operator => bool)) private _operatorApprovals;
 
-    // Used as the URI for all token types by relying on ID substitution, e.g. https://token-cdn-domain/{id}.json
-    string private _uri;
+    // ERC1155 stores the `_uri` in the 3rd slot. We leave it empty to avoid conflicts on upgrades.
+    string private __gap;
 
     mapping(address account => mapping(address operator => mapping(uint256 => uint256))) private _allowances;
 
diff --git a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol b/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
new file mode 100644
index 00000000000..515c0df2a0f
--- /dev/null
+++ b/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (token/ERC6909/extensions/draft-ER6909TokenSupply.sol)
+
+pragma solidity ^0.8.20;
+
+import {ERC6909} from "../draft-ERC6909.sol";
+import {IERC6909TokenSupply} from "../../../interfaces/draft-IERC6909.sol";
+
+contract ER6909TokenSupply is ERC6909, IERC6909TokenSupply {
+    mapping(uint256 id => uint256 totalSupply) private _totalSupplies;
+
+    function totalSupply(uint256 id) external view virtual override returns (uint256) {
+        return _totalSupplies[id];
+    }
+
+    function _update(address from, address to, uint256 id, uint256 amount) internal virtual override {
+        super._update(from, to, id, amount);
+
+        if (from == address(0)) {
+            _totalSupplies[id] += amount;
+        } else if (to == address(0)) {
+            _totalSupplies[id] -= amount;
+        }
+    }
+}
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
new file mode 100644
index 00000000000..683480e226a
--- /dev/null
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (token/ERC6909/extensions/draft-ERC6909ContentURI.sol)
+
+pragma solidity ^0.8.20;
+
+import {ERC6909} from "../draft-ERC6909.sol";
+import {IERC6909ContentURI} from "../../../interfaces/draft-IERC6909.sol";
+
+contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
+    string private _contractURI;
+    mapping(uint256 id => string) private _tokenURIs;
+
+    function contractURI() external view virtual override returns (string memory) {
+        return _contractURI;
+    }
+
+    function tokenURI(uint256 id) external view virtual override returns (string memory) {
+        return _tokenURIs[id];
+    }
+
+    function _setContractURI(string memory contractURI_) internal {
+        _contractURI = contractURI_;
+    }
+
+    function _setTokenURI(uint256 id, string memory tokenURI_) internal {
+        _tokenURIs[id] = tokenURI_;
+    }
+}
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
new file mode 100644
index 00000000000..ec8a6a16c26
--- /dev/null
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (token/ERC6909/extensions/draft-ERC6909Metadata.sol)
+
+pragma solidity ^0.8.20;
+
+import {ERC6909} from "../draft-ERC6909.sol";
+import {IERC6909Metadata} from "../../../interfaces/draft-IERC6909.sol";
+
+contract ERC6909Metadata is ERC6909, IERC6909Metadata {
+    struct TokenMetadata {
+        string uri;
+        string contentHash;
+        uint8 decimals;
+    }
+
+    mapping(uint256 => TokenMetadata) private _tokenMetadata;
+
+    function name(uint256 id) external view virtual override returns (string memory) {
+        return _tokenMetadata[id].uri;
+    }
+
+    function symbol(uint256 id) external view virtual override returns (string memory) {
+        return _tokenMetadata[id].contentHash;
+    }
+
+    function decimals(uint256 id) external view virtual override returns (uint8) {
+        return _tokenMetadata[id].decimals;
+    }
+
+    function _setTokenMetadata(uint256 id, TokenMetadata memory metadata) internal {
+        _tokenMetadata[id] = metadata;
+    }
+}

From 4dbeace86696da4c91d238ac910f2e34a81bdb8d Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 16 Dec 2024 15:40:09 -0500
Subject: [PATCH 03/47] nit

---
 contracts/token/ERC6909/draft-ERC6909.sol                   | 6 +-----
 .../token/ERC6909/extensions/draft-ER6909TokenSupply.sol    | 2 +-
 .../token/ERC6909/extensions/draft-ERC6909Metadata.sol      | 2 +-
 3 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 9bcde8b82b4..25941a3a48f 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -15,7 +15,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     // ERC1155 stores the `_uri` in the 3rd slot. We leave it empty to avoid conflicts on upgrades.
     string private __gap;
 
-    mapping(address account => mapping(address operator => mapping(uint256 => uint256))) private _allowances;
+    mapping(address account => mapping(address operator => mapping(uint256 id => uint256))) private _allowances;
 
     function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
         return interfaceId == type(IERC6909).interfaceId || super.supportsInterface(interfaceId);
@@ -37,7 +37,6 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         _allowances[_msgSender()][spender][id] = amount;
 
         emit Approval(_msgSender(), spender, id, amount);
-
         return true;
     }
 
@@ -45,13 +44,11 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         _operatorApprovals[_msgSender()][spender] = approved;
 
         emit OperatorSet(_msgSender(), spender, approved);
-
         return true;
     }
 
     function transfer(address to, uint256 id, uint256 amount) external virtual override returns (bool) {
         _update(_msgSender(), to, id, amount);
-
         return true;
     }
 
@@ -69,7 +66,6 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         }
 
         _update(from, to, id, amount);
-
         return true;
     }
 
diff --git a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol b/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
index 515c0df2a0f..0063acad7b4 100644
--- a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
+++ b/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
@@ -7,7 +7,7 @@ import {ERC6909} from "../draft-ERC6909.sol";
 import {IERC6909TokenSupply} from "../../../interfaces/draft-IERC6909.sol";
 
 contract ER6909TokenSupply is ERC6909, IERC6909TokenSupply {
-    mapping(uint256 id => uint256 totalSupply) private _totalSupplies;
+    mapping(uint256 id => uint256) private _totalSupplies;
 
     function totalSupply(uint256 id) external view virtual override returns (uint256) {
         return _totalSupplies[id];
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index ec8a6a16c26..8546d4b23f8 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -13,7 +13,7 @@ contract ERC6909Metadata is ERC6909, IERC6909Metadata {
         uint8 decimals;
     }
 
-    mapping(uint256 => TokenMetadata) private _tokenMetadata;
+    mapping(uint256 id => TokenMetadata) private _tokenMetadata;
 
     function name(uint256 id) external view virtual override returns (string memory) {
         return _tokenMetadata[id].uri;

From f038064d48bcc330b2165ec306335f370898997b Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 16 Dec 2024 16:14:22 -0500
Subject: [PATCH 04/47] add more setters `ERC6909Metadata`

---
 contracts/token/ERC6909/draft-ERC6909.sol     |  3 ---
 .../extensions/draft-ERC6909ContentURI.sol    |  8 ++++----
 .../extensions/draft-ERC6909Metadata.sol      | 20 +++++++++++++++----
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 25941a3a48f..8633b71e125 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -12,9 +12,6 @@ contract ERC6909 is Context, ERC165, IERC6909 {
 
     mapping(address account => mapping(address operator => bool)) private _operatorApprovals;
 
-    // ERC1155 stores the `_uri` in the 3rd slot. We leave it empty to avoid conflicts on upgrades.
-    string private __gap;
-
     mapping(address account => mapping(address operator => mapping(uint256 id => uint256))) private _allowances;
 
     function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index 683480e226a..85c2931e7a4 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -18,11 +18,11 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
         return _tokenURIs[id];
     }
 
-    function _setContractURI(string memory contractURI_) internal {
-        _contractURI = contractURI_;
+    function _setContractURI(string memory newContractURI) internal {
+        _contractURI = newContractURI;
     }
 
-    function _setTokenURI(uint256 id, string memory tokenURI_) internal {
-        _tokenURIs[id] = tokenURI_;
+    function _setTokenURI(uint256 id, string memory newTokenURI) internal {
+        _tokenURIs[id] = newTokenURI;
     }
 }
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index 8546d4b23f8..002e76921cd 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -8,25 +8,37 @@ import {IERC6909Metadata} from "../../../interfaces/draft-IERC6909.sol";
 
 contract ERC6909Metadata is ERC6909, IERC6909Metadata {
     struct TokenMetadata {
-        string uri;
-        string contentHash;
+        string name;
+        string symbol;
         uint8 decimals;
     }
 
     mapping(uint256 id => TokenMetadata) private _tokenMetadata;
 
     function name(uint256 id) external view virtual override returns (string memory) {
-        return _tokenMetadata[id].uri;
+        return _tokenMetadata[id].name;
     }
 
     function symbol(uint256 id) external view virtual override returns (string memory) {
-        return _tokenMetadata[id].contentHash;
+        return _tokenMetadata[id].symbol;
     }
 
     function decimals(uint256 id) external view virtual override returns (uint8) {
         return _tokenMetadata[id].decimals;
     }
 
+    function _setName(uint256 id, string memory newName) internal {
+        _tokenMetadata[id].name = newName;
+    }
+
+    function _setTokenSymbol(uint256 id, string memory newSymbol) internal {
+        _tokenMetadata[id].symbol = newSymbol;
+    }
+
+    function _setDecimals(uint256 id, uint8 newDecimals) internal {
+        _tokenMetadata[id].decimals = newDecimals;
+    }
+
     function _setTokenMetadata(uint256 id, TokenMetadata memory metadata) internal {
         _tokenMetadata[id] = metadata;
     }

From b0b0e3e49a5eb69b1d297f0b244ca57bd4d07ac8 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Thu, 19 Dec 2024 15:13:01 -0500
Subject: [PATCH 05/47] rename vars in impl and add tests

---
 contracts/token/ERC6909/draft-ERC6909.sol     |  41 ++++---
 test/token/ERC6909/ERC6909.behavior.js        | 110 ++++++++++++++++++
 test/token/ERC6909/ERC6909.test.js            |  18 +++
 .../SupportsInterface.behavior.js             |   9 ++
 4 files changed, 159 insertions(+), 19 deletions(-)
 create mode 100644 test/token/ERC6909/ERC6909.behavior.js
 create mode 100644 test/token/ERC6909/ERC6909.test.js

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 8633b71e125..efafc909338 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -8,61 +8,64 @@ import {Context} from "../../utils/Context.sol";
 import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
 
 contract ERC6909 is Context, ERC165, IERC6909 {
-    mapping(uint256 id => mapping(address account => uint256)) private _balances;
+    mapping(uint256 id => mapping(address owner => uint256)) private _balances;
 
-    mapping(address account => mapping(address operator => bool)) private _operatorApprovals;
+    mapping(address owner => mapping(address operator => bool)) private _operatorApprovals;
 
-    mapping(address account => mapping(address operator => mapping(uint256 id => uint256))) private _allowances;
+    mapping(address owner => mapping(address spender => mapping(uint256 id => uint256))) private _allowances;
 
     function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
         return interfaceId == type(IERC6909).interfaceId || super.supportsInterface(interfaceId);
     }
 
-    function balanceOf(address account, uint256 id) public view virtual override returns (uint256) {
-        return _balances[id][account];
+    function balanceOf(address owner, uint256 id) public view virtual override returns (uint256) {
+        return _balances[id][owner];
     }
 
     function allowance(address owner, address spender, uint256 id) public view virtual override returns (uint256) {
         return _allowances[owner][spender][id];
     }
 
-    function isOperator(address owner, address operator) public view virtual override returns (bool) {
-        return _operatorApprovals[owner][operator];
+    function isOperator(address owner, address spender) public view virtual override returns (bool) {
+        return _operatorApprovals[owner][spender];
     }
 
     function approve(address spender, uint256 id, uint256 amount) external virtual override returns (bool) {
-        _allowances[_msgSender()][spender][id] = amount;
+        address caller = _msgSender();
+        _allowances[caller][spender][id] = amount;
 
-        emit Approval(_msgSender(), spender, id, amount);
+        emit Approval(caller, spender, id, amount);
         return true;
     }
 
     function setOperator(address spender, bool approved) external virtual override returns (bool) {
-        _operatorApprovals[_msgSender()][spender] = approved;
+        address caller = _msgSender();
+        _operatorApprovals[caller][spender] = approved;
 
-        emit OperatorSet(_msgSender(), spender, approved);
+        emit OperatorSet(caller, spender, approved);
         return true;
     }
 
-    function transfer(address to, uint256 id, uint256 amount) external virtual override returns (bool) {
-        _update(_msgSender(), to, id, amount);
+    function transfer(address receiver, uint256 id, uint256 amount) external virtual override returns (bool) {
+        _update(_msgSender(), receiver, id, amount);
         return true;
     }
 
     function transferFrom(
-        address from,
-        address to,
+        address sender,
+        address receiver,
         uint256 id,
         uint256 amount
     ) external virtual override returns (bool) {
         address caller = _msgSender();
-        if (caller != from && !isOperator(from, caller)) {
-            if (_allowances[from][_msgSender()][id] != type(uint256).max) {
-                _allowances[from][_msgSender()][id] -= amount;
+        if (caller != sender && !isOperator(sender, caller)) {
+            uint256 currentAllowance = _allowances[sender][caller][id];
+            if (currentAllowance != type(uint256).max) {
+                _allowances[sender][_msgSender()][id] = currentAllowance - amount;
             }
         }
 
-        _update(from, to, id, amount);
+        _update(sender, receiver, id, amount);
         return true;
     }
 
diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
new file mode 100644
index 00000000000..2b25e7f99e9
--- /dev/null
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -0,0 +1,110 @@
+const { ethers } = require('hardhat');
+const { expect } = require('chai');
+
+const { shouldSupportInterfaces } = require('../../utils/introspection/SupportsInterface.behavior');
+
+function shouldBehaveLikeERC6909() {
+  const firstTokenId = 1n;
+  const secondTokenId = 2n;
+  const randomTokenId = 125523n;
+
+  const firstTokenAmount = 2000n;
+  const secondTokenAmount = 3000n;
+
+  beforeEach(async function () {
+    [this.recipient, this.proxy, this.alice, this.bruce] = this.otherAccounts;
+  });
+
+  describe('like an ERC6909', function () {
+    describe('balanceOf', function () {
+      describe("when accounts don't own tokens", function () {
+        it('return zero', async function () {
+          expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.be.equal(0);
+          expect(this.token.balanceOf(this.bruce, secondTokenId)).to.eventually.be.equal(0);
+          expect(this.token.balanceOf(this.alice, randomTokenId)).to.eventually.be.equal(0);
+        });
+      });
+
+      describe('when accounts own some tokens', function () {
+        beforeEach(async function () {
+          await this.token.$_mint(this.alice, firstTokenId, firstTokenAmount);
+          await this.token.$_mint(this.bruce, secondTokenId, secondTokenAmount);
+        });
+
+        it('returns amount owned by the given address', async function () {
+          expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.be.equal(firstTokenAmount);
+          expect(this.token.balanceOf(this.bruce, secondTokenId)).to.eventually.be.equal(secondTokenAmount);
+          expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.be.equal(0);
+        });
+      });
+    });
+
+    describe('setOperator', function () {
+      beforeEach(async function () {
+        this.tx = await this.token.connect(this.holder).setOperator(this.operator, true);
+      });
+
+      it('emits an an OperatorSet event', async function () {
+        expect(this.tx).to.emit(this.token, 'OperatorSet').withArgs(this.holder, this.operator, true);
+      });
+
+      it('should be reflected in isOperator call', async function () {
+        expect(this.token.isOperator(this.holder, this.operator)).to.eventually.be.true;
+        // not operator for other account
+        expect(this.token.isOperator(this.alice, this.operator)).to.eventually.be.false;
+      });
+
+      it('can unset the operator approval', async function () {
+        await expect(this.token.connect(this.holder).setOperator(this.operator, false))
+          .to.emit(this.token, 'OperatorSet')
+          .withArgs(this.holder, this.operator, false);
+      });
+    });
+
+    describe('approve', function () {
+      beforeEach(async function () {
+        this.tx = await this.token.connect(this.holder).approve(this.operator, firstTokenId, firstTokenAmount);
+      });
+
+      it('emits an Approval event', async function () {
+        expect(this.tx)
+          .to.emit(this.token, 'Approval')
+          .withArgs(this.holder, this.operator, firstTokenId, firstTokenAmount);
+      });
+
+      it('is reflected in allowance', async function () {
+        expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.be.equal(firstTokenAmount);
+        // not operator for other account
+        expect(this.token.allowance(this.alice, this.operator, firstTokenId)).to.eventually.be.equal(0);
+      });
+
+      it('can unset the approval', async function () {
+        await expect(this.token.connect(this.holder).approve(this.operator, firstTokenId, 0))
+          .to.emit(this.token, 'Approval')
+          .withArgs(this.holder, this.operator, firstTokenId, 0);
+        expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.be.equal(0);
+      });
+    });
+
+    describe('transfer', function () {
+      beforeEach(async function () {
+        await this.token.$_mint(this.alice, firstTokenId, firstTokenAmount);
+        await this.token.$_mint(this.bruce, secondTokenId, secondTokenAmount);
+      });
+
+      it('transfers to the zero address are allowed', async function () {
+        await expect(
+          this.token.connect(this.alice).transfer(ethers.constants.AddressZero, firstTokenId, firstTokenAmount),
+        )
+          .to.emit(this.token, 'Transfer')
+          .withArgs(this.alice, ethers.constants.AddressZero, firstTokenId, firstTokenAmount);
+      });
+    });
+
+    shouldSupportInterfaces(['ERC6909']);
+  });
+}
+
+module.exports = {
+  shouldBehaveLikeERC6909,
+};
diff --git a/test/token/ERC6909/ERC6909.test.js b/test/token/ERC6909/ERC6909.test.js
new file mode 100644
index 00000000000..facf40490e1
--- /dev/null
+++ b/test/token/ERC6909/ERC6909.test.js
@@ -0,0 +1,18 @@
+const { ethers } = require('hardhat');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+
+const { shouldBehaveLikeERC6909 } = require('./ERC6909.behavior');
+
+async function fixture() {
+  const [operator, holder, ...otherAccounts] = await ethers.getSigners();
+  const token = await ethers.deployContract('$ERC6909');
+  return { token, operator, holder, otherAccounts };
+}
+
+describe.only('ERC6909', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  shouldBehaveLikeERC6909();
+});
diff --git a/test/utils/introspection/SupportsInterface.behavior.js b/test/utils/introspection/SupportsInterface.behavior.js
index bfcddee7a5e..6e716d1304b 100644
--- a/test/utils/introspection/SupportsInterface.behavior.js
+++ b/test/utils/introspection/SupportsInterface.behavior.js
@@ -90,6 +90,15 @@ const SIGNATURES = {
   Governor: GOVERNOR_INTERFACE,
   Governor_5_3: GOVERNOR_INTERFACE.concat('getProposalId(address[],uint256[],bytes[],bytes32)'),
   ERC2981: ['royaltyInfo(uint256,uint256)'],
+  ERC6909: [
+    'balanceOf(address,uint256)',
+    'allowance(address,address,uint256)',
+    'isOperator(address,address)',
+    'transfer(address,uint256,uint256)',
+    'transferFrom(address,address,uint256,uint256)',
+    'approve(address,uint256,uint256)',
+    'setOperator(address,bool)',
+  ],
 };
 
 const INTERFACE_IDS = mapValues(SIGNATURES, interfaceId);

From 1b762457e9bc1a480b2ceae94231dc8d6a5c6555 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Thu, 19 Dec 2024 15:37:39 -0500
Subject: [PATCH 06/47] add more tests

---
 contracts/token/ERC6909/draft-ERC6909.sol     | 19 ++++++++++++++++---
 .../extensions/draft-ER6909TokenSupply.sol    |  1 -
 .../extensions/draft-ERC6909ContentURI.sol    |  1 -
 .../extensions/draft-ERC6909Metadata.sol      |  1 -
 test/token/ERC6909/ERC6909.behavior.js        |  6 ++----
 5 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index efafc909338..1e541aa7aa8 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: MIT
-// OpenZeppelin Contracts (token/ERC6909/draft-ERC6909.sol)
 
 pragma solidity ^0.8.20;
 
@@ -8,6 +7,9 @@ import {Context} from "../../utils/Context.sol";
 import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
 
 contract ERC6909 is Context, ERC165, IERC6909 {
+    error ERC6909InsufficientBalance(address sender, uint256 balance, uint256 needed, uint256 id);
+    error ERC6909InsufficientAllowance(address spender, uint256 allowance, uint256 needed, uint256 id);
+
     mapping(uint256 id => mapping(address owner => uint256)) private _balances;
 
     mapping(address owner => mapping(address operator => bool)) private _operatorApprovals;
@@ -61,7 +63,12 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         if (caller != sender && !isOperator(sender, caller)) {
             uint256 currentAllowance = _allowances[sender][caller][id];
             if (currentAllowance != type(uint256).max) {
-                _allowances[sender][_msgSender()][id] = currentAllowance - amount;
+                if (currentAllowance < amount) {
+                    revert ERC6909InsufficientAllowance(caller, currentAllowance, amount, id);
+                }
+                unchecked {
+                    _allowances[sender][_msgSender()][id] = currentAllowance - amount;
+                }
             }
         }
 
@@ -73,7 +80,13 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         address caller = _msgSender();
 
         if (from != address(0)) {
-            _balances[id][from] -= amount;
+            uint256 fromBalance = _balances[id][from];
+            if (fromBalance < amount) {
+                revert ERC6909InsufficientBalance(from, fromBalance, amount, id);
+            }
+            unchecked {
+                _balances[id][from] -= amount;
+            }
         }
         if (to != address(0)) {
             _balances[id][to] += amount;
diff --git a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol b/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
index 0063acad7b4..1cdc39985dc 100644
--- a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
+++ b/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: MIT
-// OpenZeppelin Contracts (token/ERC6909/extensions/draft-ER6909TokenSupply.sol)
 
 pragma solidity ^0.8.20;
 
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index 85c2931e7a4..9f9c9bd7f5d 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: MIT
-// OpenZeppelin Contracts (token/ERC6909/extensions/draft-ERC6909ContentURI.sol)
 
 pragma solidity ^0.8.20;
 
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index 002e76921cd..d244f5d7ba0 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: MIT
-// OpenZeppelin Contracts (token/ERC6909/extensions/draft-ERC6909Metadata.sol)
 
 pragma solidity ^0.8.20;
 
diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
index 2b25e7f99e9..1cd25248bb6 100644
--- a/test/token/ERC6909/ERC6909.behavior.js
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -93,11 +93,9 @@ function shouldBehaveLikeERC6909() {
       });
 
       it('transfers to the zero address are allowed', async function () {
-        await expect(
-          this.token.connect(this.alice).transfer(ethers.constants.AddressZero, firstTokenId, firstTokenAmount),
-        )
+        await expect(this.token.connect(this.alice).transfer(ethers.ZeroAddress, firstTokenId, firstTokenAmount))
           .to.emit(this.token, 'Transfer')
-          .withArgs(this.alice, ethers.constants.AddressZero, firstTokenId, firstTokenAmount);
+          .withArgs(this.alice, this.alice, ethers.ZeroAddress, firstTokenId, firstTokenAmount);
       });
     });
 

From 9ae0429fcf00bfc1ed4c0fa2840ddbf9bc7b5040 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 20 Dec 2024 10:32:49 -0500
Subject: [PATCH 07/47] add more tests

---
 test/token/ERC6909/ERC6909.behavior.js | 57 ++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
index 1cd25248bb6..5cf23ced0b5 100644
--- a/test/token/ERC6909/ERC6909.behavior.js
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -96,9 +96,66 @@ function shouldBehaveLikeERC6909() {
         await expect(this.token.connect(this.alice).transfer(ethers.ZeroAddress, firstTokenId, firstTokenAmount))
           .to.emit(this.token, 'Transfer')
           .withArgs(this.alice, this.alice, ethers.ZeroAddress, firstTokenId, firstTokenAmount);
+
+        // expect(this.token.balanceOf(ethers.ZeroAddress, firstTokenId)).to.eventually.equal(firstTokenAmount); TODO: fix
+        expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(0);
+      });
+
+      it('reverts when insufficient balance', async function () {
+        await expect(this.token.connect(this.alice).transfer(this.bruce, firstTokenId, firstTokenAmount + 1n))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InsufficientBalance')
+          .withArgs(this.alice, firstTokenAmount, firstTokenAmount + 1n, firstTokenId);
+      });
+    });
+
+    describe('transferFrom', function () {
+      beforeEach(async function () {
+        await this.token.$_mint(this.alice, firstTokenId, firstTokenAmount);
+        await this.token.$_mint(this.bruce, secondTokenId, secondTokenAmount);
+      });
+
+      it('transfer from self', async function () {
+        await this.token.connect(this.alice).transferFrom(this.alice, this.bruce, firstTokenId, firstTokenAmount);
+        expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(0);
+        expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.equal(firstTokenAmount);
+      });
+
+      describe('with approval', async function () {
+        beforeEach(async function () {
+          await this.token.connect(this.alice).approve(this.operator, firstTokenId, firstTokenAmount - 1n);
+          this.tx = await this.token
+            .connect(this.operator)
+            .transferFrom(this.alice, this.bruce, firstTokenId, firstTokenAmount - 1n);
+        });
+
+        it('reverts when insufficient allowance', async function () {
+          await expect(this.token.connect(this.operator).transferFrom(this.alice, this.bruce, firstTokenId, 1))
+            .to.be.revertedWithCustomError(this.token, 'ERC6909InsufficientAllowance')
+            .withArgs(this.operator, 0, 1, firstTokenId);
+        });
+
+        it('should emit transfer event', async function () {
+          expect(this.tx)
+            .to.emit(this.token, 'Transfer')
+            .withArgs(this.operator, this.alice, this.bruce, firstTokenId, firstTokenAmount - 1n);
+        });
+
+        it('should update approval', async function () {
+          expect(this.token.allowance(this.alice, this.operator, firstTokenId)).to.eventually.equal(0);
+        });
+
+        it("shouldn't reduce allowance when infinite", async function () {
+          await this.token.connect(this.bruce).approve(this.operator, secondTokenId, ethers.MaxUint256);
+          await this.token
+            .connect(this.operator)
+            .transferFrom(this.bruce, this.alice, secondTokenId, secondTokenAmount);
+          expect(this.token.allowance(this.bruce, this.operator, secondTokenId)).to.eventually.equal(ethers.MaxUint256);
+        });
       });
     });
 
+    describe('with operator approval', function () {});
+
     shouldSupportInterfaces(['ERC6909']);
   });
 }

From f69bdfdd9dc89c126b55b2b6f2bcd9c9b67cd0f7 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 20 Dec 2024 15:27:16 -0500
Subject: [PATCH 08/47] additional testing

---
 contracts/token/ERC6909/draft-ERC6909.sol | 20 +++++++-
 test/token/ERC6909/ERC6909.behavior.js    | 24 +++++++++-
 test/token/ERC6909/ERC6909.test.js        | 58 ++++++++++++++++++++++-
 3 files changed, 99 insertions(+), 3 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 1e541aa7aa8..c84822a8761 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -9,6 +9,8 @@ import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
 contract ERC6909 is Context, ERC165, IERC6909 {
     error ERC6909InsufficientBalance(address sender, uint256 balance, uint256 needed, uint256 id);
     error ERC6909InsufficientAllowance(address spender, uint256 allowance, uint256 needed, uint256 id);
+    error ERC6909InvalidReceiver(address receiver);
+    error ERC6909InvalidSender(address sender);
 
     mapping(uint256 id => mapping(address owner => uint256)) private _balances;
 
@@ -72,10 +74,20 @@ contract ERC6909 is Context, ERC165, IERC6909 {
             }
         }
 
-        _update(sender, receiver, id, amount);
+        _transfer(sender, receiver, id, amount);
         return true;
     }
 
+    function _transfer(address from, address to, uint256 id, uint256 amount) internal {
+        if (from == address(0)) {
+            revert ERC6909InvalidSender(address(0));
+        }
+        if (to == address(0)) {
+            revert ERC6909InvalidReceiver(address(0));
+        }
+        _update(from, to, id, amount);
+    }
+
     function _update(address from, address to, uint256 id, uint256 amount) internal virtual {
         address caller = _msgSender();
 
@@ -96,10 +108,16 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     function _mint(address to, uint256 id, uint256 amount) internal {
+        if (to == address(0)) {
+            revert ERC6909InvalidReceiver(address(0));
+        }
         _update(address(0), to, id, amount);
     }
 
     function _burn(address from, uint256 id, uint256 amount) internal {
+        if (from == address(0)) {
+            revert ERC6909InvalidSender(address(0));
+        }
         _update(from, address(0), id, amount);
     }
 }
diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
index 5cf23ced0b5..44e98311917 100644
--- a/test/token/ERC6909/ERC6909.behavior.js
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -154,7 +154,29 @@ function shouldBehaveLikeERC6909() {
       });
     });
 
-    describe('with operator approval', function () {});
+    describe('with operator approval', function () {
+      beforeEach(async function () {
+        await this.token.connect(this.holder).setOperator(this.operator, true);
+        await this.token.$_mint(this.holder, firstTokenId, firstTokenAmount);
+      });
+
+      it('operator can transfer', async function () {
+        await expect(
+          this.token.connect(this.operator).transferFrom(this.holder, this.alice, firstTokenId, firstTokenAmount),
+        )
+          .to.emit(this.token, 'Transfer')
+          .withArgs(this.operator, this.holder, this.alice, firstTokenId, firstTokenAmount);
+        expect(this.token.balanceOf(this.holder, firstTokenId)).to.eventually.equal(0);
+        expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(firstTokenAmount);
+      });
+
+      it('operator transfer does not reduce allowance', async function () {
+        // Also give allowance
+        await this.token.connect(this.holder).approve(this.operator, firstTokenId, firstTokenAmount);
+        await this.token.connect(this.operator).transferFrom(this.holder, this.alice, firstTokenId, firstTokenAmount);
+        expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.equal(firstTokenAmount);
+      });
+    });
 
     shouldSupportInterfaces(['ERC6909']);
   });
diff --git a/test/token/ERC6909/ERC6909.test.js b/test/token/ERC6909/ERC6909.test.js
index facf40490e1..240b01df807 100644
--- a/test/token/ERC6909/ERC6909.test.js
+++ b/test/token/ERC6909/ERC6909.test.js
@@ -2,6 +2,7 @@ const { ethers } = require('hardhat');
 const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 
 const { shouldBehaveLikeERC6909 } = require('./ERC6909.behavior');
+const { expect } = require('chai');
 
 async function fixture() {
   const [operator, holder, ...otherAccounts] = await ethers.getSigners();
@@ -9,10 +10,65 @@ async function fixture() {
   return { token, operator, holder, otherAccounts };
 }
 
-describe.only('ERC6909', function () {
+describe('ERC6909', function () {
   beforeEach(async function () {
     Object.assign(this, await loadFixture(fixture));
   });
 
   shouldBehaveLikeERC6909();
+
+  describe('internal functions', function () {
+    const tokenId = 1990n;
+    const mintValue = 9001n;
+    const burnValue = 3000n;
+
+    describe('_mint', function () {
+      it('reverts with a zero destination address', async function () {
+        await expect(this.token.$_mint(ethers.ZeroAddress, tokenId, mintValue))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidReceiver')
+          .withArgs(ethers.ZeroAddress);
+      });
+
+      describe('with minted tokens', function () {
+        beforeEach(async function () {
+          this.tx = await this.token.connect(this.operator).$_mint(this.holder, tokenId, mintValue);
+        });
+
+        it('emits a Transfer event from 0 address', async function () {
+          expect(this.tx)
+            .to.emit(this.token, 'Transfer')
+            .withArgs(this.operator, ethers.ZeroAddress, this.holder, tokenId, mintValue);
+        });
+
+        it('credits the minted token value', async function () {
+          expect(this.token.balanceOf(this.holder, tokenId)).to.eventually.be.equal(mintValue);
+        });
+      });
+    });
+
+    describe('_burn', function () {
+      it('reverts with a zero from address', async function () {
+        await expect(this.token.$_burn(ethers.ZeroAddress, tokenId, burnValue))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidSender')
+          .withArgs(ethers.ZeroAddress);
+      });
+
+      describe('with burned tokens', function () {
+        beforeEach(async function () {
+          await this.token.connect(this.operator).$_mint(this.holder, tokenId, mintValue);
+          this.tx = await this.token.connect(this.operator).$_burn(this.holder, tokenId, burnValue);
+        });
+
+        it('emits a Transfer event to 0 address', async function () {
+          expect(this.tx)
+            .to.emit(this.token, 'Transfer')
+            .withArgs(this.operator, this.holder, ethers.ZeroAddress, tokenId, burnValue);
+        });
+
+        it('debits the burned token value', async function () {
+          expect(this.token.balanceOf(this.holder, tokenId)).to.eventually.be.equal(mintValue - burnValue);
+        });
+      });
+    });
+  });
 });

From 7d78b5a2b9a11474178dad360a22761f6755bee7 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 20 Dec 2024 16:42:01 -0500
Subject: [PATCH 09/47] await when checking logs

---
 test/token/ERC6909/ERC6909.behavior.js | 6 +++---
 test/token/ERC6909/ERC6909.test.js     | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
index 44e98311917..abc6b06ff68 100644
--- a/test/token/ERC6909/ERC6909.behavior.js
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -45,7 +45,7 @@ function shouldBehaveLikeERC6909() {
       });
 
       it('emits an an OperatorSet event', async function () {
-        expect(this.tx).to.emit(this.token, 'OperatorSet').withArgs(this.holder, this.operator, true);
+        await expect(this.tx).to.emit(this.token, 'OperatorSet').withArgs(this.holder, this.operator, true);
       });
 
       it('should be reflected in isOperator call', async function () {
@@ -67,7 +67,7 @@ function shouldBehaveLikeERC6909() {
       });
 
       it('emits an Approval event', async function () {
-        expect(this.tx)
+        await expect(this.tx)
           .to.emit(this.token, 'Approval')
           .withArgs(this.holder, this.operator, firstTokenId, firstTokenAmount);
       });
@@ -135,7 +135,7 @@ function shouldBehaveLikeERC6909() {
         });
 
         it('should emit transfer event', async function () {
-          expect(this.tx)
+          await expect(this.tx)
             .to.emit(this.token, 'Transfer')
             .withArgs(this.operator, this.alice, this.bruce, firstTokenId, firstTokenAmount - 1n);
         });
diff --git a/test/token/ERC6909/ERC6909.test.js b/test/token/ERC6909/ERC6909.test.js
index 240b01df807..f2dc83afcf7 100644
--- a/test/token/ERC6909/ERC6909.test.js
+++ b/test/token/ERC6909/ERC6909.test.js
@@ -35,7 +35,7 @@ describe('ERC6909', function () {
         });
 
         it('emits a Transfer event from 0 address', async function () {
-          expect(this.tx)
+          await expect(this.tx)
             .to.emit(this.token, 'Transfer')
             .withArgs(this.operator, ethers.ZeroAddress, this.holder, tokenId, mintValue);
         });
@@ -60,7 +60,7 @@ describe('ERC6909', function () {
         });
 
         it('emits a Transfer event to 0 address', async function () {
-          expect(this.tx)
+          await expect(this.tx)
             .to.emit(this.token, 'Transfer')
             .withArgs(this.operator, this.holder, ethers.ZeroAddress, tokenId, burnValue);
         });

From 6abfd920ce44c6ecf69b43d90a257eca1d389a65 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 30 Dec 2024 11:30:52 -0500
Subject: [PATCH 10/47] address comments and fix tests

---
 contracts/token/ERC6909/draft-ERC6909.sol |  8 ++--
 test/token/ERC6909/ERC6909.behavior.js    | 52 ++++++++++++-----------
 test/token/ERC6909/ERC6909.test.js        |  4 +-
 3 files changed, 34 insertions(+), 30 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index c84822a8761..23786b9f047 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -51,7 +51,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     function transfer(address receiver, uint256 id, uint256 amount) external virtual override returns (bool) {
-        _update(_msgSender(), receiver, id, amount);
+        _transfer(_msgSender(), receiver, id, amount);
         return true;
     }
 
@@ -63,13 +63,13 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     ) external virtual override returns (bool) {
         address caller = _msgSender();
         if (caller != sender && !isOperator(sender, caller)) {
-            uint256 currentAllowance = _allowances[sender][caller][id];
+            uint256 currentAllowance = allowance(sender, caller, id);
             if (currentAllowance != type(uint256).max) {
                 if (currentAllowance < amount) {
                     revert ERC6909InsufficientAllowance(caller, currentAllowance, amount, id);
                 }
                 unchecked {
-                    _allowances[sender][_msgSender()][id] = currentAllowance - amount;
+                    _allowances[sender][caller][id] = currentAllowance - amount;
                 }
             }
         }
@@ -92,7 +92,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         address caller = _msgSender();
 
         if (from != address(0)) {
-            uint256 fromBalance = _balances[id][from];
+            uint256 fromBalance = balanceOf(from, id);
             if (fromBalance < amount) {
                 revert ERC6909InsufficientBalance(from, fromBalance, amount, id);
             }
diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
index abc6b06ff68..518761edcb0 100644
--- a/test/token/ERC6909/ERC6909.behavior.js
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -19,9 +19,9 @@ function shouldBehaveLikeERC6909() {
     describe('balanceOf', function () {
       describe("when accounts don't own tokens", function () {
         it('return zero', async function () {
-          expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.be.equal(0);
-          expect(this.token.balanceOf(this.bruce, secondTokenId)).to.eventually.be.equal(0);
-          expect(this.token.balanceOf(this.alice, randomTokenId)).to.eventually.be.equal(0);
+          await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.be.equal(0);
+          await expect(this.token.balanceOf(this.bruce, secondTokenId)).to.eventually.be.equal(0);
+          await expect(this.token.balanceOf(this.alice, randomTokenId)).to.eventually.be.equal(0);
         });
       });
 
@@ -32,9 +32,9 @@ function shouldBehaveLikeERC6909() {
         });
 
         it('returns amount owned by the given address', async function () {
-          expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.be.equal(firstTokenAmount);
-          expect(this.token.balanceOf(this.bruce, secondTokenId)).to.eventually.be.equal(secondTokenAmount);
-          expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.be.equal(0);
+          await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.be.equal(firstTokenAmount);
+          await expect(this.token.balanceOf(this.bruce, secondTokenId)).to.eventually.be.equal(secondTokenAmount);
+          await expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.be.equal(0);
         });
       });
     });
@@ -49,9 +49,9 @@ function shouldBehaveLikeERC6909() {
       });
 
       it('should be reflected in isOperator call', async function () {
-        expect(this.token.isOperator(this.holder, this.operator)).to.eventually.be.true;
+        await expect(this.token.isOperator(this.holder, this.operator)).to.eventually.be.true;
         // not operator for other account
-        expect(this.token.isOperator(this.alice, this.operator)).to.eventually.be.false;
+        await expect(this.token.isOperator(this.alice, this.operator)).to.eventually.be.false;
       });
 
       it('can unset the operator approval', async function () {
@@ -73,16 +73,18 @@ function shouldBehaveLikeERC6909() {
       });
 
       it('is reflected in allowance', async function () {
-        expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.be.equal(firstTokenAmount);
+        await expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.be.equal(
+          firstTokenAmount,
+        );
         // not operator for other account
-        expect(this.token.allowance(this.alice, this.operator, firstTokenId)).to.eventually.be.equal(0);
+        await expect(this.token.allowance(this.alice, this.operator, firstTokenId)).to.eventually.be.equal(0);
       });
 
       it('can unset the approval', async function () {
         await expect(this.token.connect(this.holder).approve(this.operator, firstTokenId, 0))
           .to.emit(this.token, 'Approval')
           .withArgs(this.holder, this.operator, firstTokenId, 0);
-        expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.be.equal(0);
+        await expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.be.equal(0);
       });
     });
 
@@ -92,13 +94,11 @@ function shouldBehaveLikeERC6909() {
         await this.token.$_mint(this.bruce, secondTokenId, secondTokenAmount);
       });
 
-      it('transfers to the zero address are allowed', async function () {
-        await expect(this.token.connect(this.alice).transfer(ethers.ZeroAddress, firstTokenId, firstTokenAmount))
-          .to.emit(this.token, 'Transfer')
-          .withArgs(this.alice, this.alice, ethers.ZeroAddress, firstTokenId, firstTokenAmount);
-
-        // expect(this.token.balanceOf(ethers.ZeroAddress, firstTokenId)).to.eventually.equal(firstTokenAmount); TODO: fix
-        expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(0);
+      it('transfers to the zero address are blocked', async function () {
+        await expect(
+          this.token.connect(this.alice).transfer(ethers.ZeroAddress, firstTokenId, firstTokenAmount),
+        ).to.be.revertedWithCustomError(this.token, 'ERC6909InvalidReceiver');
+        await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(firstTokenAmount);
       });
 
       it('reverts when insufficient balance', async function () {
@@ -116,8 +116,8 @@ function shouldBehaveLikeERC6909() {
 
       it('transfer from self', async function () {
         await this.token.connect(this.alice).transferFrom(this.alice, this.bruce, firstTokenId, firstTokenAmount);
-        expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(0);
-        expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.equal(firstTokenAmount);
+        await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(0);
+        await expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.equal(firstTokenAmount);
       });
 
       describe('with approval', async function () {
@@ -149,7 +149,9 @@ function shouldBehaveLikeERC6909() {
           await this.token
             .connect(this.operator)
             .transferFrom(this.bruce, this.alice, secondTokenId, secondTokenAmount);
-          expect(this.token.allowance(this.bruce, this.operator, secondTokenId)).to.eventually.equal(ethers.MaxUint256);
+          await expect(this.token.allowance(this.bruce, this.operator, secondTokenId)).to.eventually.equal(
+            ethers.MaxUint256,
+          );
         });
       });
     });
@@ -166,15 +168,17 @@ function shouldBehaveLikeERC6909() {
         )
           .to.emit(this.token, 'Transfer')
           .withArgs(this.operator, this.holder, this.alice, firstTokenId, firstTokenAmount);
-        expect(this.token.balanceOf(this.holder, firstTokenId)).to.eventually.equal(0);
-        expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(firstTokenAmount);
+        await expect(this.token.balanceOf(this.holder, firstTokenId)).to.eventually.equal(0);
+        await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(firstTokenAmount);
       });
 
       it('operator transfer does not reduce allowance', async function () {
         // Also give allowance
         await this.token.connect(this.holder).approve(this.operator, firstTokenId, firstTokenAmount);
         await this.token.connect(this.operator).transferFrom(this.holder, this.alice, firstTokenId, firstTokenAmount);
-        expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.equal(firstTokenAmount);
+        await expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.equal(
+          firstTokenAmount,
+        );
       });
     });
 
diff --git a/test/token/ERC6909/ERC6909.test.js b/test/token/ERC6909/ERC6909.test.js
index f2dc83afcf7..80242493900 100644
--- a/test/token/ERC6909/ERC6909.test.js
+++ b/test/token/ERC6909/ERC6909.test.js
@@ -41,7 +41,7 @@ describe('ERC6909', function () {
         });
 
         it('credits the minted token value', async function () {
-          expect(this.token.balanceOf(this.holder, tokenId)).to.eventually.be.equal(mintValue);
+          await expect(this.token.balanceOf(this.holder, tokenId)).to.eventually.be.equal(mintValue);
         });
       });
     });
@@ -66,7 +66,7 @@ describe('ERC6909', function () {
         });
 
         it('debits the burned token value', async function () {
-          expect(this.token.balanceOf(this.holder, tokenId)).to.eventually.be.equal(mintValue - burnValue);
+          await expect(this.token.balanceOf(this.holder, tokenId)).to.eventually.be.equal(mintValue - burnValue);
         });
       });
     });

From 15ece65877d5bd126e91f9f5fddc2d72de7fe27b Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 30 Dec 2024 13:14:50 -0500
Subject: [PATCH 11/47] add test for total supply

---
 .../extensions/ER6909TokenSupply.test.js      | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 test/token/ERC6909/extensions/ER6909TokenSupply.test.js

diff --git a/test/token/ERC6909/extensions/ER6909TokenSupply.test.js b/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
new file mode 100644
index 00000000000..b47c8536567
--- /dev/null
+++ b/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
@@ -0,0 +1,34 @@
+const { ethers } = require('hardhat');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+const { expect } = require('chai');
+
+const { shouldBehaveLikeERC6909 } = require('../ERC6909.behavior');
+
+async function fixture() {
+  const [operator, holder, ...otherAccounts] = await ethers.getSigners();
+  const token = await ethers.deployContract('$ER6909TokenSupply');
+  return { token, operator, holder, otherAccounts };
+}
+
+describe.only('ERC6909TokenSupply', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  shouldBehaveLikeERC6909();
+
+  describe('totalSupply', function () {
+    beforeEach(async function () {
+      await this.token.$_mint(this.holder, 1n, 1000n);
+    });
+
+    it('Minting tokens increases the total supply', async function () {
+      return expect(this.token.totalSupply(1n)).to.eventually.be.equal(1000n);
+    });
+
+    it('Burning tokens decreases the total supply', async function () {
+      await this.token.$_burn(this.holder, 1n, 500n);
+      return expect(this.token.totalSupply(1n)).to.eventually.be.equal(500n);
+    });
+  });
+});

From 499f79b0ac1872f827d6b1a681c277920c6c219e Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 30 Dec 2024 14:55:20 -0500
Subject: [PATCH 12/47] format

---
 test/token/ERC6909/extensions/ER6909TokenSupply.test.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/token/ERC6909/extensions/ER6909TokenSupply.test.js b/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
index b47c8536567..6124b1ff333 100644
--- a/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
+++ b/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
@@ -22,11 +22,11 @@ describe.only('ERC6909TokenSupply', function () {
       await this.token.$_mint(this.holder, 1n, 1000n);
     });
 
-    it('Minting tokens increases the total supply', async function () {
+    it('minting tokens increases the total supply', async function () {
       return expect(this.token.totalSupply(1n)).to.eventually.be.equal(1000n);
     });
 
-    it('Burning tokens decreases the total supply', async function () {
+    it('burning tokens decreases the total supply', async function () {
       await this.token.$_burn(this.holder, 1n, 500n);
       return expect(this.token.totalSupply(1n)).to.eventually.be.equal(500n);
     });

From d79198d736ab456c3cad43bb9e8fe965064b1aa3 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 30 Dec 2024 16:26:14 -0500
Subject: [PATCH 13/47] add tests

---
 test/token/ERC6909/ERC6909.behavior.js                  | 8 ++++++++
 test/token/ERC6909/extensions/ER6909TokenSupply.test.js | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
index 518761edcb0..abbc8c78e98 100644
--- a/test/token/ERC6909/ERC6909.behavior.js
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -106,6 +106,14 @@ function shouldBehaveLikeERC6909() {
           .to.be.revertedWithCustomError(this.token, 'ERC6909InsufficientBalance')
           .withArgs(this.alice, firstTokenAmount, firstTokenAmount + 1n, firstTokenId);
       });
+
+      it('emits event and transfers tokens', async function () {
+        await expect(this.token.connect(this.alice).transfer(this.bruce, firstTokenId, firstTokenAmount))
+          .to.emit(this.token, 'Transfer')
+          .withArgs(this.alice, this.alice, this.bruce, firstTokenId, firstTokenAmount);
+        await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(0);
+        return expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.equal(firstTokenAmount);
+      });
     });
 
     describe('transferFrom', function () {
diff --git a/test/token/ERC6909/extensions/ER6909TokenSupply.test.js b/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
index 6124b1ff333..0d8c732dde3 100644
--- a/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
+++ b/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
@@ -10,7 +10,7 @@ async function fixture() {
   return { token, operator, holder, otherAccounts };
 }
 
-describe.only('ERC6909TokenSupply', function () {
+describe('ERC6909TokenSupply', function () {
   beforeEach(async function () {
     Object.assign(this, await loadFixture(fixture));
   });

From 85196e78641b707a66553484244f9223f4401658 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 30 Dec 2024 18:12:52 -0500
Subject: [PATCH 14/47] add internal function test

---
 test/token/ERC6909/ERC6909.test.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test/token/ERC6909/ERC6909.test.js b/test/token/ERC6909/ERC6909.test.js
index 80242493900..dedd7274556 100644
--- a/test/token/ERC6909/ERC6909.test.js
+++ b/test/token/ERC6909/ERC6909.test.js
@@ -70,5 +70,11 @@ describe('ERC6909', function () {
         });
       });
     });
+
+    it('reverts when transferring from the zero address', async function () {
+      await expect(this.token.$_transfer(ethers.ZeroAddress, this.holder, 1n, 1n))
+        .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidSender')
+        .withArgs(ethers.ZeroAddress);
+    });
   });
 });

From 89690059cece5fb9b279f4dcf26712db29660218 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Thu, 2 Jan 2025 16:19:03 -0500
Subject: [PATCH 15/47] add changesets

---
 .changeset/brown-turkeys-marry.md | 5 +++++
 .changeset/dirty-bananas-shake.md | 5 +++++
 .changeset/proud-cooks-do.md      | 5 +++++
 .changeset/ten-hats-begin.md      | 5 +++++
 4 files changed, 20 insertions(+)
 create mode 100644 .changeset/brown-turkeys-marry.md
 create mode 100644 .changeset/dirty-bananas-shake.md
 create mode 100644 .changeset/proud-cooks-do.md
 create mode 100644 .changeset/ten-hats-begin.md

diff --git a/.changeset/brown-turkeys-marry.md b/.changeset/brown-turkeys-marry.md
new file mode 100644
index 00000000000..0440f0d9464
--- /dev/null
+++ b/.changeset/brown-turkeys-marry.md
@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`ER6909TokenSupply`: Add an extension of ERC6909 which tracks total supply for each token id.
diff --git a/.changeset/dirty-bananas-shake.md b/.changeset/dirty-bananas-shake.md
new file mode 100644
index 00000000000..4e10a427c40
--- /dev/null
+++ b/.changeset/dirty-bananas-shake.md
@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`ERC6909ContentURI`: Add an extension of ERC6909 which adds content URI functionality.
diff --git a/.changeset/proud-cooks-do.md b/.changeset/proud-cooks-do.md
new file mode 100644
index 00000000000..e3d4331aeb2
--- /dev/null
+++ b/.changeset/proud-cooks-do.md
@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`ERC6909Metadata`: Add an extension of ERC6909 which adds metadata functionality.
diff --git a/.changeset/ten-hats-begin.md b/.changeset/ten-hats-begin.md
new file mode 100644
index 00000000000..393e0e7db5d
--- /dev/null
+++ b/.changeset/ten-hats-begin.md
@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`ERC6909`: Add a standard implmentation of ERC6909.

From 607c11933640bc1ba717409cd5a3c561086b7ac3 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Thu, 2 Jan 2025 16:31:18 -0500
Subject: [PATCH 16/47] fix spelling

---
 .changeset/ten-hats-begin.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.changeset/ten-hats-begin.md b/.changeset/ten-hats-begin.md
index 393e0e7db5d..bb7ab77e2ff 100644
--- a/.changeset/ten-hats-begin.md
+++ b/.changeset/ten-hats-begin.md
@@ -2,4 +2,4 @@
 'openzeppelin-solidity': minor
 ---
 
-`ERC6909`: Add a standard implmentation of ERC6909.
+`ERC6909`: Add a standard implementation of ERC6909.

From 57631119f3a92e5724ecda18eed8aa73f8e9ad5f Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 3 Jan 2025 12:37:47 -0500
Subject: [PATCH 17/47] Add tests for `ERC6909Metadata`

---
 .../extensions/draft-ERC6909Metadata.sol      |  2 +-
 .../extensions/ERC6909Metadata.test.js        | 72 +++++++++++++++++++
 2 files changed, 73 insertions(+), 1 deletion(-)
 create mode 100644 test/token/ERC6909/extensions/ERC6909Metadata.test.js

diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index d244f5d7ba0..fd946234a2a 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -30,7 +30,7 @@ contract ERC6909Metadata is ERC6909, IERC6909Metadata {
         _tokenMetadata[id].name = newName;
     }
 
-    function _setTokenSymbol(uint256 id, string memory newSymbol) internal {
+    function _setSymbol(uint256 id, string memory newSymbol) internal {
         _tokenMetadata[id].symbol = newSymbol;
     }
 
diff --git a/test/token/ERC6909/extensions/ERC6909Metadata.test.js b/test/token/ERC6909/extensions/ERC6909Metadata.test.js
new file mode 100644
index 00000000000..270a0bcddc8
--- /dev/null
+++ b/test/token/ERC6909/extensions/ERC6909Metadata.test.js
@@ -0,0 +1,72 @@
+const { ethers } = require('hardhat');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+const { expect } = require('chai');
+
+async function fixture() {
+  const [operator, holder, ...otherAccounts] = await ethers.getSigners();
+  const token = await ethers.deployContract('$ERC6909Metadata');
+  return { token, operator, holder, otherAccounts };
+}
+
+describe('ERC6909Metadata', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  describe('name', function () {
+    it('is empty string be default', async function () {
+      return expect(this.token.name(1n)).to.eventually.equal('');
+    });
+
+    it('can be set by dedicated setter', async function () {
+      await this.token.$_setName(1n, 'My Token');
+      await expect(this.token.name(1n)).to.eventually.equal('My Token');
+
+      // Only set for the specified token ID
+      return expect(this.token.name(2n)).to.eventually.equal('');
+    });
+
+    it('can be set by global setter', async function () {
+      await this.token.$_setTokenMetadata(1n, { name: 'My Token', symbol: '', decimals: '0' });
+      return expect(this.token.name(1n)).to.eventually.equal('My Token');
+    });
+  });
+
+  describe('symbol', function () {
+    it('is empty string be default', async function () {
+      return expect(this.token.symbol(1n)).to.eventually.equal('');
+    });
+
+    it('can be set by dedicated setter', async function () {
+      await this.token.$_setSymbol(1n, 'MTK');
+      await expect(this.token.symbol(1n)).to.eventually.equal('MTK');
+
+      // Only set for the specified token ID
+      return expect(this.token.symbol(2n)).to.eventually.equal('');
+    });
+
+    it('can be set by global setter', async function () {
+      await this.token.$_setTokenMetadata(1n, { name: '', symbol: 'MTK', decimals: '0' });
+      return expect(this.token.symbol(1n)).to.eventually.equal('MTK');
+    });
+  });
+
+  describe('decimals', function () {
+    it('is 0 by default', async function () {
+      return expect(this.token.decimals(1n)).to.eventually.equal(0);
+    });
+
+    it('can be set by dedicated setter', async function () {
+      await this.token.$_setDecimals(1n, 18);
+      await expect(this.token.decimals(1n)).to.eventually.equal(18);
+
+      // Only set for the specified token ID
+      return expect(this.token.decimals(2n)).to.eventually.equal(0);
+    });
+
+    it('can be set by global setter', async function () {
+      await this.token.$_setTokenMetadata(1n, { name: '', symbol: '', decimals: '18' });
+      return expect(this.token.decimals(1n)).to.eventually.equal(18);
+    });
+  });
+});

From 673124c820bb8a6b4af9af6aa209c27f8437ab50 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 3 Jan 2025 15:17:38 -0500
Subject: [PATCH 18/47] test `ERC6909ContentURI`

---
 .../extensions/ERC6909ContentURI.test.js      | 40 +++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 test/token/ERC6909/extensions/ERC6909ContentURI.test.js

diff --git a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
new file mode 100644
index 00000000000..ba87b74b761
--- /dev/null
+++ b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
@@ -0,0 +1,40 @@
+const { ethers } = require('hardhat');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+const { expect } = require('chai');
+
+async function fixture() {
+  const [operator, holder, ...otherAccounts] = await ethers.getSigners();
+  const token = await ethers.deployContract('$ERC6909ContentURI');
+  return { token, operator, holder, otherAccounts };
+}
+
+describe('ERC6909ContentURI', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  describe('contractURI', function () {
+    it('is empty string be default', async function () {
+      return expect(this.token.contractURI()).to.eventually.equal('');
+    });
+
+    it('is settable by internal setter', async function () {
+      await this.token.$_setContractURI('https://example.com');
+      return expect(this.token.contractURI()).to.eventually.equal('https://example.com');
+    });
+  });
+
+  describe('tokenURI', function () {
+    it('is empty string be default', async function () {
+      return expect(this.token.tokenURI(1n)).to.eventually.equal('');
+    });
+
+    it('can be set by dedicated setter', async function () {
+      await this.token.$_setTokenURI(1n, 'https://example.com/1');
+      await expect(this.token.tokenURI(1n)).to.eventually.equal('https://example.com/1');
+
+      // Only set for the specified token ID
+      return expect(this.token.tokenURI(2n)).to.eventually.equal('');
+    });
+  });
+});

From ff3ee754e2b7b7b6c82844c0d61810846aa9fd46 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 10 Jan 2025 15:04:49 -0500
Subject: [PATCH 19/47] Add docs

---
 contracts/token/ERC6909/draft-ERC6909.sol     | 45 +++++++++++++++++++
 .../extensions/draft-ER6909TokenSupply.sol    |  5 +++
 .../extensions/draft-ERC6909ContentURI.sol    |  2 +
 .../extensions/draft-ERC6909Metadata.sol      |  6 +++
 4 files changed, 58 insertions(+)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 23786b9f047..8d5282b5484 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -6,6 +6,10 @@ import {IERC6909} from "../../interfaces/draft-IERC6909.sol";
 import {Context} from "../../utils/Context.sol";
 import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
 
+/**
+ * @dev Basic implementation of ERC6909.
+ * See https://eips.ethereum.org/EIPS/eip-6909
+ */
 contract ERC6909 is Context, ERC165, IERC6909 {
     error ERC6909InsufficientBalance(address sender, uint256 balance, uint256 needed, uint256 id);
     error ERC6909InsufficientAllowance(address spender, uint256 allowance, uint256 needed, uint256 id);
@@ -18,22 +22,27 @@ contract ERC6909 is Context, ERC165, IERC6909 {
 
     mapping(address owner => mapping(address spender => mapping(uint256 id => uint256))) private _allowances;
 
+    /// @inheritdoc IERC165
     function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
         return interfaceId == type(IERC6909).interfaceId || super.supportsInterface(interfaceId);
     }
 
+    /// @inheritdoc IERC6909
     function balanceOf(address owner, uint256 id) public view virtual override returns (uint256) {
         return _balances[id][owner];
     }
 
+    /// @inheritdoc IERC6909
     function allowance(address owner, address spender, uint256 id) public view virtual override returns (uint256) {
         return _allowances[owner][spender][id];
     }
 
+    /// @inheritdoc IERC6909
     function isOperator(address owner, address spender) public view virtual override returns (bool) {
         return _operatorApprovals[owner][spender];
     }
 
+    /// @inheritdoc IERC6909
     function approve(address spender, uint256 id, uint256 amount) external virtual override returns (bool) {
         address caller = _msgSender();
         _allowances[caller][spender][id] = amount;
@@ -42,6 +51,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         return true;
     }
 
+    /// @inheritdoc IERC6909
     function setOperator(address spender, bool approved) external virtual override returns (bool) {
         address caller = _msgSender();
         _operatorApprovals[caller][spender] = approved;
@@ -50,11 +60,13 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         return true;
     }
 
+    /// @inheritdoc IERC6909
     function transfer(address receiver, uint256 id, uint256 amount) external virtual override returns (bool) {
         _transfer(_msgSender(), receiver, id, amount);
         return true;
     }
 
+    /// @inheritdoc IERC6909
     function transferFrom(
         address sender,
         address receiver,
@@ -78,6 +90,16 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         return true;
     }
 
+    /**
+     * @dev Moves `amount` of token `id` from `from` to `to` without checking for approvals.
+     *
+     * This internal function is equivalent to {transfer}, and can be used to
+     * e.g. implement automatic token fees, slashing mechanisms, etc.
+     *
+     * Emits a {Transfer} event.
+     *
+     * NOTE: This function is not virtual, {_update} should be overridden instead.
+     */
     function _transfer(address from, address to, uint256 id, uint256 amount) internal {
         if (from == address(0)) {
             revert ERC6909InvalidSender(address(0));
@@ -88,6 +110,13 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         _update(from, to, id, amount);
     }
 
+    /**
+     * @dev Transfers `amount` of token `id` from `from` to `to`, or alternatively mints (or burns) if `from`
+     * (or `to`) is the zero address. All customizations to transfers, mints, and burns should be done by overriding
+     * this function.
+     *
+     * Emits a {Transfer} event.
+     */
     function _update(address from, address to, uint256 id, uint256 amount) internal virtual {
         address caller = _msgSender();
 
@@ -107,6 +136,14 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         emit Transfer(caller, from, to, id, amount);
     }
 
+    /**
+     * @dev Creates `amount` of token `id` and assigns them to `account`, by transferring it from address(0).
+     * Relies on the `_update` mechanism
+     *
+     * Emits a {Transfer} event with `from` set to the zero address.
+     *
+     * NOTE: This function is not virtual, {_update} should be overridden instead.
+     */
     function _mint(address to, uint256 id, uint256 amount) internal {
         if (to == address(0)) {
             revert ERC6909InvalidReceiver(address(0));
@@ -114,6 +151,14 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         _update(address(0), to, id, amount);
     }
 
+    /**
+     * @dev Destroys a `amount` of token `id` from `account`.
+     * Relies on the `_update` mechanism.
+     *
+     * Emits a {Transfer} event with `to` set to the zero address.
+     *
+     * NOTE: This function is not virtual, {_update} should be overridden instead
+     */
     function _burn(address from, uint256 id, uint256 amount) internal {
         if (from == address(0)) {
             revert ERC6909InvalidSender(address(0));
diff --git a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol b/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
index 1cdc39985dc..8586637bac0 100644
--- a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
+++ b/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
@@ -5,9 +5,14 @@ pragma solidity ^0.8.20;
 import {ERC6909} from "../draft-ERC6909.sol";
 import {IERC6909TokenSupply} from "../../../interfaces/draft-IERC6909.sol";
 
+/**
+ * @dev Implementation of the Token Supply extension defined in ERC6909.
+ * Tracks the total supply of each token id individually.
+ */
 contract ER6909TokenSupply is ERC6909, IERC6909TokenSupply {
     mapping(uint256 id => uint256) private _totalSupplies;
 
+    /// @inheritdoc IERC6909TokenSupply
     function totalSupply(uint256 id) external view virtual override returns (uint256) {
         return _totalSupplies[id];
     }
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index 9f9c9bd7f5d..ca3517421df 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -9,10 +9,12 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
     string private _contractURI;
     mapping(uint256 id => string) private _tokenURIs;
 
+    /// @inheritdoc IERC6909ContentURI
     function contractURI() external view virtual override returns (string memory) {
         return _contractURI;
     }
 
+    /// @inheritdoc IERC6909ContentURI
     function tokenURI(uint256 id) external view virtual override returns (string memory) {
         return _tokenURIs[id];
     }
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index fd946234a2a..fd184ce3cf4 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -5,6 +5,9 @@ pragma solidity ^0.8.20;
 import {ERC6909} from "../draft-ERC6909.sol";
 import {IERC6909Metadata} from "../../../interfaces/draft-IERC6909.sol";
 
+/**
+ * @dev Implementation of the Metadata extension defined in ERC6909. Exposes the name, symbol, and decimals of each token id.
+ */
 contract ERC6909Metadata is ERC6909, IERC6909Metadata {
     struct TokenMetadata {
         string name;
@@ -14,14 +17,17 @@ contract ERC6909Metadata is ERC6909, IERC6909Metadata {
 
     mapping(uint256 id => TokenMetadata) private _tokenMetadata;
 
+    /// @inheritdoc IERC6909Metadata
     function name(uint256 id) external view virtual override returns (string memory) {
         return _tokenMetadata[id].name;
     }
 
+    /// @inheritdoc IERC6909Metadata
     function symbol(uint256 id) external view virtual override returns (string memory) {
         return _tokenMetadata[id].symbol;
     }
 
+    /// @inheritdoc IERC6909Metadata
     function decimals(uint256 id) external view virtual override returns (uint8) {
         return _tokenMetadata[id].decimals;
     }

From 1f347348fe243b996381ce71d1005f73ff7a10c5 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 10 Jan 2025 16:28:05 -0500
Subject: [PATCH 20/47] add content uri docs

---
 contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol | 3 +++
 contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol   | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index ca3517421df..5f8c43d3921 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -5,6 +5,9 @@ pragma solidity ^0.8.20;
 import {ERC6909} from "../draft-ERC6909.sol";
 import {IERC6909ContentURI} from "../../../interfaces/draft-IERC6909.sol";
 
+/**
+ * @dev Implementation of the Content URI extension defined in ERC6909.
+ */
 contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
     string private _contractURI;
     mapping(uint256 id => string) private _tokenURIs;
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index fd184ce3cf4..d662043504f 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -44,6 +44,9 @@ contract ERC6909Metadata is ERC6909, IERC6909Metadata {
         _tokenMetadata[id].decimals = newDecimals;
     }
 
+    /**
+     * @dev Sets the metadata for a given token `id` to the provided `metadata` struct. Overwrites any previous metadata for this token id.
+     */
     function _setTokenMetadata(uint256 id, TokenMetadata memory metadata) internal {
         _tokenMetadata[id] = metadata;
     }

From 2d9bc74b5230b32670fe56fb92d553fc45b89d7c Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 13 Jan 2025 17:22:33 -1000
Subject: [PATCH 21/47] start on additional docs

---
 contracts/token/ERC6909/README.adoc  | 30 ++++++++++++++++++++++++++++
 docs/modules/ROOT/pages/erc6909.adoc |  5 +++++
 2 files changed, 35 insertions(+)
 create mode 100644 contracts/token/ERC6909/README.adoc
 create mode 100644 docs/modules/ROOT/pages/erc6909.adoc

diff --git a/contracts/token/ERC6909/README.adoc b/contracts/token/ERC6909/README.adoc
new file mode 100644
index 00000000000..b93cf8507d8
--- /dev/null
+++ b/contracts/token/ERC6909/README.adoc
@@ -0,0 +1,30 @@
+= ERC-6909
+
+[.readme-notice]
+NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/token/erc6909
+
+This set of interfaces and contracts are all related to the https://eips.ethereum.org/EIPS/eip-6909[ERC-6909 Minimal Multi-Token Interface].
+
+The ERC consists of four interfaces which fulfill different roles, found here as {IERC6909}, {IERC6909Metadata}, {IERC6909ContentURI}, and {IERC6909TokenSupply}.
+
+Implementations are provided for each of the 4 interfaces defined in the EIP.
+
+== Core
+
+{{IERC6909}}
+
+{{ERC6909}}
+
+== Extensions
+
+{{IERC6909Metadata}}
+
+{{IERC6909ContentURI}}
+
+{{IERC6909TokenSupply}}
+
+{{ERC6909ContentURI}}
+
+{{ERC6909Metadata}}
+
+{{ERC6909TokenSupply}}
\ No newline at end of file
diff --git a/docs/modules/ROOT/pages/erc6909.adoc b/docs/modules/ROOT/pages/erc6909.adoc
new file mode 100644
index 00000000000..2848e9f5f59
--- /dev/null
+++ b/docs/modules/ROOT/pages/erc6909.adoc
@@ -0,0 +1,5 @@
+= ERC-6909
+
+ERC-6909 is a draft EIP that draws on ERC-1155 and learnings since it was published in 2018. The main goals of ERC-6909 is to decrease gas costs and complexity--this is mainly accomplished by removing batching and callbacks.
+
+TIP: To understand the inspiration for a multi token standard, see the xref:erc1155.adoc#multi-token-standard[multi token standard] section within the EIP-1155 docs.
\ No newline at end of file

From 14a06a00a4aafc9bbaa69f7e0048f397218bb0b1 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Wed, 15 Jan 2025 18:28:13 -1000
Subject: [PATCH 22/47] add reference contract

---
 .../mocks/docs/token/ERC6909/GameItems.sol    | 20 ++++++++++++++++
 docs/modules/ROOT/pages/erc6909.adoc          | 24 ++++++++++++++++++-
 2 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 contracts/mocks/docs/token/ERC6909/GameItems.sol

diff --git a/contracts/mocks/docs/token/ERC6909/GameItems.sol b/contracts/mocks/docs/token/ERC6909/GameItems.sol
new file mode 100644
index 00000000000..4bc18eeb560
--- /dev/null
+++ b/contracts/mocks/docs/token/ERC6909/GameItems.sol
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import {ERC6909} from "../../../../token/ERC6909/draft-ERC6909.sol";
+
+contract GameItems is ERC6909 {
+    uint256 public constant GOLD = 0;
+    uint256 public constant SILVER = 1;
+    uint256 public constant THORS_HAMMER = 2;
+    uint256 public constant SWORD = 3;
+    uint256 public constant SHIELD = 4;
+
+    constructor() {
+        _mint(msg.sender, GOLD, 10 ** 18);
+        _mint(msg.sender, SILVER, 10 ** 27);
+        _mint(msg.sender, THORS_HAMMER, 1);
+        _mint(msg.sender, SWORD, 10 ** 9);
+        _mint(msg.sender, SHIELD, 10 ** 9);
+    }
+}
diff --git a/docs/modules/ROOT/pages/erc6909.adoc b/docs/modules/ROOT/pages/erc6909.adoc
index 2848e9f5f59..497309db864 100644
--- a/docs/modules/ROOT/pages/erc6909.adoc
+++ b/docs/modules/ROOT/pages/erc6909.adoc
@@ -2,4 +2,26 @@
 
 ERC-6909 is a draft EIP that draws on ERC-1155 and learnings since it was published in 2018. The main goals of ERC-6909 is to decrease gas costs and complexity--this is mainly accomplished by removing batching and callbacks.
 
-TIP: To understand the inspiration for a multi token standard, see the xref:erc1155.adoc#multi-token-standard[multi token standard] section within the EIP-1155 docs.
\ No newline at end of file
+TIP: To understand the inspiration for a multi token standard, see the xref:erc1155.adoc#multi-token-standard[multi token standard] section within the EIP-1155 docs.
+
+== Changes from ERC-1155
+There are three main changes from ERC-1155 which are as follows:
+1. The removal of batch operations.
+2. The removal of transfer callbacks.
+3. Granularization in approvals--approvals can be set globally (as operators) or as amounts per token (inspired by ERC20).
+
+== Constructing an ERC-6909 Token Contract
+
+We'll use ERC-6909 to track multiple items in a game, each having their own unique attributes. All item types with by minted to the deployer of the contract, which we can later transfer to players.
+
+For simplicity, we will mint all items in the constructor--however, minting functionality could be added to the contract to min on demand to players.
+
+TIP: For an overview of minting mechanisms, check out xref:erc20-supply.adoc[Creating ERC-20 Supply].
+
+Here's what a contract for tokenized items might look like:
+
+[source,solidity]
+----
+include::api:example$token/ERC6909/GameItems.sol[]
+----
+

From 7089ec5948a2dc603b8e9511e5a5c00af51c2baf Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Thu, 16 Jan 2025 10:10:56 -1000
Subject: [PATCH 23/47] further documentation

---
 contracts/interfaces/draft-IERC6909.sol |  2 ++
 docs/modules/ROOT/pages/erc6909.adoc    | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/contracts/interfaces/draft-IERC6909.sol b/contracts/interfaces/draft-IERC6909.sol
index 12151e88656..51b5df05daa 100644
--- a/contracts/interfaces/draft-IERC6909.sol
+++ b/contracts/interfaces/draft-IERC6909.sol
@@ -108,6 +108,8 @@ interface IERC6909ContentURI is IERC6909 {
 
     /**
      * @dev Returns the URI for the token of type `id`.
+     *
+     * NOTE: MUST replace occurrences of {id} in the returned URI string by the client.
      */
     function tokenURI(uint256 id) external view returns (string memory);
 }
diff --git a/docs/modules/ROOT/pages/erc6909.adoc b/docs/modules/ROOT/pages/erc6909.adoc
index 497309db864..644bd2f456f 100644
--- a/docs/modules/ROOT/pages/erc6909.adoc
+++ b/docs/modules/ROOT/pages/erc6909.adoc
@@ -25,3 +25,21 @@ Here's what a contract for tokenized items might look like:
 include::api:example$token/ERC6909/GameItems.sol[]
 ----
 
+Note that the vanilla xref:api:token/ERC6909.adoc#ERC6909[`ERC6909`] implementation does not have any concept of decimals, but the xref:api:token/ERC6909.adoc#ERC6909Metadata[`ERC6909Metadata`] extension does. This is very useful when some (or all) of the tokens represented by the ERC-6909 contract are fungible. Additionally, there is no content URI functionality in the base implementation, but the xref:api:token/ERC6909.adoc#ERC6909ContentURI[`ERC6909ContentURI`] extension adds it.
+
+Once the contract is deployed, we will be able to query the deployer’s balance:
+[source,javascript]
+----
+> gameItems.balanceOf(deployerAddress,3)
+1000000000
+----
+
+We can transfer items to player accounts:
+[source,javascript]
+----
+> gameItems.transfer(playerAddress, 2, 1)
+> gameItems.balanceOf(playerAddress, 2)
+1
+> gameItems.balanceOf(deployerAddress, 2)
+0
+----
\ No newline at end of file

From a6601c84e249556274b958992cd4eefceb08da7d Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Thu, 16 Jan 2025 10:35:13 -1000
Subject: [PATCH 24/47] Update docs and fix incorrectly named file

---
 contracts/interfaces/README.adoc                     | 12 ++++++++++++
 contracts/interfaces/draft-IERC6909.sol              |  2 +-
 ...9TokenSupply.sol => draft-ERC6909TokenSupply.sol} |  3 ++-
 docs/modules/ROOT/nav.adoc                           |  1 +
 docs/modules/ROOT/pages/erc6909.adoc                 |  7 ++++---
 ...okenSupply.test.js => ERC6909TokenSupply.test.js} |  2 +-
 6 files changed, 21 insertions(+), 6 deletions(-)
 rename contracts/token/ERC6909/extensions/{draft-ER6909TokenSupply.sol => draft-ERC6909TokenSupply.sol} (84%)
 rename test/token/ERC6909/extensions/{ER6909TokenSupply.test.js => ERC6909TokenSupply.test.js} (94%)

diff --git a/contracts/interfaces/README.adoc b/contracts/interfaces/README.adoc
index 61aae05d167..25717bcda03 100644
--- a/contracts/interfaces/README.adoc
+++ b/contracts/interfaces/README.adoc
@@ -40,6 +40,10 @@ are useful to interact with third party contracts that implement them.
 - {IERC5313}
 - {IERC5805}
 - {IERC6372}
+- {IERC6909}
+- {IERC6909ContentURI}
+- {IERC6909Metadata}
+- {IERC6909TokenSupply}
 - {IERC7674}
 
 == Detailed ABI
@@ -82,4 +86,12 @@ are useful to interact with third party contracts that implement them.
 
 {{IERC6372}}
 
+{{IERC6909}}
+
+{{IERC6909ContentURI}}
+
+{{IERC6909Metadata}}
+
+{{IERC6909TokenSupply}}
+
 {{IERC7674}}
diff --git a/contracts/interfaces/draft-IERC6909.sol b/contracts/interfaces/draft-IERC6909.sol
index 51b5df05daa..bcab244fb94 100644
--- a/contracts/interfaces/draft-IERC6909.sol
+++ b/contracts/interfaces/draft-IERC6909.sol
@@ -109,7 +109,7 @@ interface IERC6909ContentURI is IERC6909 {
     /**
      * @dev Returns the URI for the token of type `id`.
      *
-     * NOTE: MUST replace occurrences of {id} in the returned URI string by the client.
+     * NOTE: MUST replace occurrences of `{id}` in the returned URI string by the client.
      */
     function tokenURI(uint256 id) external view returns (string memory);
 }
diff --git a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol b/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
similarity index 84%
rename from contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
rename to contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
index 8586637bac0..d20cb7717b9 100644
--- a/contracts/token/ERC6909/extensions/draft-ER6909TokenSupply.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
@@ -9,7 +9,7 @@ import {IERC6909TokenSupply} from "../../../interfaces/draft-IERC6909.sol";
  * @dev Implementation of the Token Supply extension defined in ERC6909.
  * Tracks the total supply of each token id individually.
  */
-contract ER6909TokenSupply is ERC6909, IERC6909TokenSupply {
+contract ERC6909TokenSupply is ERC6909, IERC6909TokenSupply {
     mapping(uint256 id => uint256) private _totalSupplies;
 
     /// @inheritdoc IERC6909TokenSupply
@@ -17,6 +17,7 @@ contract ER6909TokenSupply is ERC6909, IERC6909TokenSupply {
         return _totalSupplies[id];
     }
 
+    /// @dev Override the `_update` function to update the total supply of each token id as necessary.
     function _update(address from, address to, uint256 id, uint256 amount) internal virtual override {
         super._update(from, to, id, amount);
 
diff --git a/docs/modules/ROOT/nav.adoc b/docs/modules/ROOT/nav.adoc
index 15af8b40ea3..59164ff9110 100644
--- a/docs/modules/ROOT/nav.adoc
+++ b/docs/modules/ROOT/nav.adoc
@@ -12,6 +12,7 @@
 *** xref:erc20-supply.adoc[Creating Supply]
 ** xref:erc721.adoc[ERC-721]
 ** xref:erc1155.adoc[ERC-1155]
+** xref:erc6909.adoc[ERC-6909]
 ** xref:erc4626.adoc[ERC-4626]
 
 * xref:governance.adoc[Governance]
diff --git a/docs/modules/ROOT/pages/erc6909.adoc b/docs/modules/ROOT/pages/erc6909.adoc
index 644bd2f456f..8ece07543b1 100644
--- a/docs/modules/ROOT/pages/erc6909.adoc
+++ b/docs/modules/ROOT/pages/erc6909.adoc
@@ -6,9 +6,10 @@ TIP: To understand the inspiration for a multi token standard, see the xref:erc1
 
 == Changes from ERC-1155
 There are three main changes from ERC-1155 which are as follows:
-1. The removal of batch operations.
-2. The removal of transfer callbacks.
-3. Granularization in approvals--approvals can be set globally (as operators) or as amounts per token (inspired by ERC20).
+
+. The removal of batch operations.
+. The removal of transfer callbacks.
+. Granularization in approvals--approvals can be set globally (as operators) or as amounts per token (inspired by ERC20).
 
 == Constructing an ERC-6909 Token Contract
 
diff --git a/test/token/ERC6909/extensions/ER6909TokenSupply.test.js b/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
similarity index 94%
rename from test/token/ERC6909/extensions/ER6909TokenSupply.test.js
rename to test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
index 0d8c732dde3..be2c990a2b6 100644
--- a/test/token/ERC6909/extensions/ER6909TokenSupply.test.js
+++ b/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
@@ -6,7 +6,7 @@ const { shouldBehaveLikeERC6909 } = require('../ERC6909.behavior');
 
 async function fixture() {
   const [operator, holder, ...otherAccounts] = await ethers.getSigners();
-  const token = await ethers.deployContract('$ER6909TokenSupply');
+  const token = await ethers.deployContract('$ERC6909TokenSupply');
   return { token, operator, holder, otherAccounts };
 }
 

From e711da686426e4f4781869a3644d43ef4c00bceb Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 17 Jan 2025 09:40:52 -1000
Subject: [PATCH 25/47] update docs

---
 contracts/mocks/docs/token/ERC6909/GameItems.sol | 12 +++++++++---
 docs/modules/ROOT/pages/erc6909.adoc             |  4 ++--
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/contracts/mocks/docs/token/ERC6909/GameItems.sol b/contracts/mocks/docs/token/ERC6909/GameItems.sol
index 4bc18eeb560..022395b19fc 100644
--- a/contracts/mocks/docs/token/ERC6909/GameItems.sol
+++ b/contracts/mocks/docs/token/ERC6909/GameItems.sol
@@ -1,9 +1,9 @@
 // SPDX-License-Identifier: MIT
 pragma solidity ^0.8.20;
 
-import {ERC6909} from "../../../../token/ERC6909/draft-ERC6909.sol";
+import {ERC6909Metadata} from "../../../../token/ERC6909/extensions/draft-ERC6909Metadata.sol";
 
-contract GameItems is ERC6909 {
+contract GameItems is ERC6909Metadata {
     uint256 public constant GOLD = 0;
     uint256 public constant SILVER = 1;
     uint256 public constant THORS_HAMMER = 2;
@@ -11,8 +11,14 @@ contract GameItems is ERC6909 {
     uint256 public constant SHIELD = 4;
 
     constructor() {
+        _setDecimals(GOLD, 18);
+        _setDecimals(SILVER, 18);
+        // Default decimals is 0
+        _setDecimals(SWORD, 9);
+        _setDecimals(SHIELD, 9);
+
         _mint(msg.sender, GOLD, 10 ** 18);
-        _mint(msg.sender, SILVER, 10 ** 27);
+        _mint(msg.sender, SILVER, 10_000 ** 18);
         _mint(msg.sender, THORS_HAMMER, 1);
         _mint(msg.sender, SWORD, 10 ** 9);
         _mint(msg.sender, SHIELD, 10 ** 9);
diff --git a/docs/modules/ROOT/pages/erc6909.adoc b/docs/modules/ROOT/pages/erc6909.adoc
index 8ece07543b1..c5c53be8d7f 100644
--- a/docs/modules/ROOT/pages/erc6909.adoc
+++ b/docs/modules/ROOT/pages/erc6909.adoc
@@ -13,7 +13,7 @@ There are three main changes from ERC-1155 which are as follows:
 
 == Constructing an ERC-6909 Token Contract
 
-We'll use ERC-6909 to track multiple items in a game, each having their own unique attributes. All item types with by minted to the deployer of the contract, which we can later transfer to players.
+We'll use ERC-6909 to track multiple items in a game, each having their own unique attributes. All item types with by minted to the deployer of the contract, which we can later transfer to players. We'll also use the xref:api:token/ERC6909.adoc#ERC6909Metadata[`ERC6909Metadata`] extension to add decimals to our fungible items (the vanilla ERC-6909 implementation does not have decimals).
 
 For simplicity, we will mint all items in the constructor--however, minting functionality could be added to the contract to min on demand to players.
 
@@ -26,7 +26,7 @@ Here's what a contract for tokenized items might look like:
 include::api:example$token/ERC6909/GameItems.sol[]
 ----
 
-Note that the vanilla xref:api:token/ERC6909.adoc#ERC6909[`ERC6909`] implementation does not have any concept of decimals, but the xref:api:token/ERC6909.adoc#ERC6909Metadata[`ERC6909Metadata`] extension does. This is very useful when some (or all) of the tokens represented by the ERC-6909 contract are fungible. Additionally, there is no content URI functionality in the base implementation, but the xref:api:token/ERC6909.adoc#ERC6909ContentURI[`ERC6909ContentURI`] extension adds it.
+Note that there is no content URI functionality in the base implementation, but the xref:api:token/ERC6909.adoc#ERC6909ContentURI[`ERC6909ContentURI`] extension adds it. Additionally, the base implementation does not track total supplies, but the xref:api:token/ERC6909.adoc#ERC6909TokenSupply[`ERC6909TokenSupply`] extension tracks the total supply of each token id.
 
 Once the contract is deployed, we will be able to query the deployer’s balance:
 [source,javascript]

From 361f81272fbd49f5b94b5986d30aa65855acc807 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 17 Jan 2025 11:54:40 -1000
Subject: [PATCH 26/47] move interface

---
 contracts/token/ERC6909/README.adoc                        | 2 +-
 contracts/token/ERC6909/draft-ERC6909.sol                  | 2 +-
 contracts/{interfaces => token/ERC6909}/draft-IERC6909.sol | 0
 3 files changed, 2 insertions(+), 2 deletions(-)
 rename contracts/{interfaces => token/ERC6909}/draft-IERC6909.sol (100%)

diff --git a/contracts/token/ERC6909/README.adoc b/contracts/token/ERC6909/README.adoc
index b93cf8507d8..48218f8692f 100644
--- a/contracts/token/ERC6909/README.adoc
+++ b/contracts/token/ERC6909/README.adoc
@@ -7,7 +7,7 @@ This set of interfaces and contracts are all related to the https://eips.ethereu
 
 The ERC consists of four interfaces which fulfill different roles, found here as {IERC6909}, {IERC6909Metadata}, {IERC6909ContentURI}, and {IERC6909TokenSupply}.
 
-Implementations are provided for each of the 4 interfaces defined in the EIP.
+Implementations are provided for each of the 4 interfaces defined in the ERC.
 
 == Core
 
diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 8d5282b5484..cc75e98260b 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -2,7 +2,7 @@
 
 pragma solidity ^0.8.20;
 
-import {IERC6909} from "../../interfaces/draft-IERC6909.sol";
+import {IERC6909} from "./draft-IERC6909.sol";
 import {Context} from "../../utils/Context.sol";
 import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
 
diff --git a/contracts/interfaces/draft-IERC6909.sol b/contracts/token/ERC6909/draft-IERC6909.sol
similarity index 100%
rename from contracts/interfaces/draft-IERC6909.sol
rename to contracts/token/ERC6909/draft-IERC6909.sol

From a2e9c98de981356fa8ec45f69ead947252858248 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 17 Jan 2025 11:57:58 -1000
Subject: [PATCH 27/47] add interface reference to interfaces folder

---
 contracts/interfaces/draft-IERC6909.sol    | 4 ++++
 contracts/token/ERC6909/draft-ERC6909.sol  | 2 +-
 contracts/token/ERC6909/draft-IERC6909.sol | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)
 create mode 100644 contracts/interfaces/draft-IERC6909.sol

diff --git a/contracts/interfaces/draft-IERC6909.sol b/contracts/interfaces/draft-IERC6909.sol
new file mode 100644
index 00000000000..0c05f81c944
--- /dev/null
+++ b/contracts/interfaces/draft-IERC6909.sol
@@ -0,0 +1,4 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import {IERC6909, IERC6909Metadata, IERC6909ContentURI, IERC6909TokenSupply} from "../token/ERC6909/draft-IERC6909.sol";
diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index cc75e98260b..8d5282b5484 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -2,7 +2,7 @@
 
 pragma solidity ^0.8.20;
 
-import {IERC6909} from "./draft-IERC6909.sol";
+import {IERC6909} from "../../interfaces/draft-IERC6909.sol";
 import {Context} from "../../utils/Context.sol";
 import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
 
diff --git a/contracts/token/ERC6909/draft-IERC6909.sol b/contracts/token/ERC6909/draft-IERC6909.sol
index bcab244fb94..33688dad540 100644
--- a/contracts/token/ERC6909/draft-IERC6909.sol
+++ b/contracts/token/ERC6909/draft-IERC6909.sol
@@ -2,7 +2,7 @@
 
 pragma solidity ^0.8.20;
 
-import {IERC165} from "../utils/introspection/IERC165.sol";
+import {IERC165} from "../../utils/introspection/IERC165.sol";
 
 /**
  * @dev Required interface of an ERC-6909 compliant contract, as defined in the

From 78bf584c8e31da061c1cce9b36ba3dff449150eb Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 17 Jan 2025 12:14:43 -1000
Subject: [PATCH 28/47] emit events on uri changes

---
 .../ERC6909/extensions/draft-ERC6909ContentURI.sol | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index 5f8c43d3921..1547d7a4e29 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -12,6 +12,16 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
     string private _contractURI;
     mapping(uint256 id => string) private _tokenURIs;
 
+    /**
+     * @dev Event emitted when the contract URI is changed. See https://eips.ethereum.org/EIPS/eip-7572[ERC-7572] for details.
+     */
+    event ContractURIUpdated();
+
+    /**
+     * @dev See {IERC4906-MetadataUpdate}. This contract does not inherit {IERC4906} as it requires {IERC721}.
+     */
+    event MetadataUpdate(uint256 _tokenId);
+
     /// @inheritdoc IERC6909ContentURI
     function contractURI() external view virtual override returns (string memory) {
         return _contractURI;
@@ -24,9 +34,13 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
 
     function _setContractURI(string memory newContractURI) internal {
         _contractURI = newContractURI;
+
+        emit ContractURIUpdated();
     }
 
     function _setTokenURI(uint256 id, string memory newTokenURI) internal {
         _tokenURIs[id] = newTokenURI;
+
+        emit MetadataUpdate(id);
     }
 }

From 521335ca9b1785f3d97a7943d10948c136be2b8d Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 17 Jan 2025 12:25:53 -1000
Subject: [PATCH 29/47] move game items file for 6909

---
 .../docs/token/ERC6909/{GameItems.sol => ERC6909GameItems.sol}  | 2 +-
 docs/modules/ROOT/pages/erc6909.adoc                            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
 rename contracts/mocks/docs/token/ERC6909/{GameItems.sol => ERC6909GameItems.sol} (94%)

diff --git a/contracts/mocks/docs/token/ERC6909/GameItems.sol b/contracts/mocks/docs/token/ERC6909/ERC6909GameItems.sol
similarity index 94%
rename from contracts/mocks/docs/token/ERC6909/GameItems.sol
rename to contracts/mocks/docs/token/ERC6909/ERC6909GameItems.sol
index 022395b19fc..611e1dd667b 100644
--- a/contracts/mocks/docs/token/ERC6909/GameItems.sol
+++ b/contracts/mocks/docs/token/ERC6909/ERC6909GameItems.sol
@@ -3,7 +3,7 @@ pragma solidity ^0.8.20;
 
 import {ERC6909Metadata} from "../../../../token/ERC6909/extensions/draft-ERC6909Metadata.sol";
 
-contract GameItems is ERC6909Metadata {
+contract ERC6909GameItems is ERC6909Metadata {
     uint256 public constant GOLD = 0;
     uint256 public constant SILVER = 1;
     uint256 public constant THORS_HAMMER = 2;
diff --git a/docs/modules/ROOT/pages/erc6909.adoc b/docs/modules/ROOT/pages/erc6909.adoc
index c5c53be8d7f..37985ddfd45 100644
--- a/docs/modules/ROOT/pages/erc6909.adoc
+++ b/docs/modules/ROOT/pages/erc6909.adoc
@@ -23,7 +23,7 @@ Here's what a contract for tokenized items might look like:
 
 [source,solidity]
 ----
-include::api:example$token/ERC6909/GameItems.sol[]
+include::api:example$token/ERC6909/ERC6909GameItems.sol[]
 ----
 
 Note that there is no content URI functionality in the base implementation, but the xref:api:token/ERC6909.adoc#ERC6909ContentURI[`ERC6909ContentURI`] extension adds it. Additionally, the base implementation does not track total supplies, but the xref:api:token/ERC6909.adoc#ERC6909TokenSupply[`ERC6909TokenSupply`] extension tracks the total supply of each token id.

From d630d84ec2586b7404ba5079161ffb20af02229f Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 17 Jan 2025 14:54:53 -1000
Subject: [PATCH 30/47] check that event is emitted on uri set

---
 test/token/ERC6909/extensions/ERC6909ContentURI.test.js | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
index ba87b74b761..579b7c1cccb 100644
--- a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
+++ b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
@@ -22,6 +22,10 @@ describe('ERC6909ContentURI', function () {
       await this.token.$_setContractURI('https://example.com');
       return expect(this.token.contractURI()).to.eventually.equal('https://example.com');
     });
+
+    it('emits an event when set', async function () {
+      await expect(this.token.$_setContractURI('https://example.com')).to.emit(this.token, 'ContractURIUpdated');
+    });
   });
 
   describe('tokenURI', function () {
@@ -36,5 +40,9 @@ describe('ERC6909ContentURI', function () {
       // Only set for the specified token ID
       return expect(this.token.tokenURI(2n)).to.eventually.equal('');
     });
+
+    it('emits an event when set', async function () {
+      await expect(this.token.$_setTokenURI(1n, 'https://example.com/1')).to.emit(this.token, 'MetadataUpdate').withArgs(1n);
+    });
   });
 });

From b3c83c760d1251a2a20ae6065f61f05d68b8f95b Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 17 Jan 2025 15:03:52 -1000
Subject: [PATCH 31/47] fix lint

---
 test/token/ERC6909/extensions/ERC6909ContentURI.test.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
index 579b7c1cccb..105da7a22d6 100644
--- a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
+++ b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
@@ -42,7 +42,9 @@ describe('ERC6909ContentURI', function () {
     });
 
     it('emits an event when set', async function () {
-      await expect(this.token.$_setTokenURI(1n, 'https://example.com/1')).to.emit(this.token, 'MetadataUpdate').withArgs(1n);
+      await expect(this.token.$_setTokenURI(1n, 'https://example.com/1'))
+        .to.emit(this.token, 'MetadataUpdate')
+        .withArgs(1n);
     });
   });
 });

From 9f6506bee375f7103c81a826e2811a30ba2d7b92 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 20 Jan 2025 12:34:06 -0500
Subject: [PATCH 32/47] Apply suggestions from code review

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
---
 contracts/token/ERC6909/draft-ERC6909.sol | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 8d5282b5484..667cfa4eeb1 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -7,7 +7,7 @@ import {Context} from "../../utils/Context.sol";
 import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
 
 /**
- * @dev Basic implementation of ERC6909.
+ * @dev Implementation of ERC-6909.
  * See https://eips.ethereum.org/EIPS/eip-6909
  */
 contract ERC6909 is Context, ERC165, IERC6909 {
@@ -43,7 +43,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     /// @inheritdoc IERC6909
-    function approve(address spender, uint256 id, uint256 amount) external virtual override returns (bool) {
+    function approve(address spender, uint256 id, uint256 amount) public virtual override returns (bool) {
         address caller = _msgSender();
         _allowances[caller][spender][id] = amount;
 
@@ -52,7 +52,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     /// @inheritdoc IERC6909
-    function setOperator(address spender, bool approved) external virtual override returns (bool) {
+    function setOperator(address spender, bool approved) public virtual override returns (bool) {
         address caller = _msgSender();
         _operatorApprovals[caller][spender] = approved;
 
@@ -61,7 +61,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     /// @inheritdoc IERC6909
-    function transfer(address receiver, uint256 id, uint256 amount) external virtual override returns (bool) {
+    function transfer(address receiver, uint256 id, uint256 amount) public virtual override returns (bool) {
         _transfer(_msgSender(), receiver, id, amount);
         return true;
     }
@@ -72,7 +72,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         address receiver,
         uint256 id,
         uint256 amount
-    ) external virtual override returns (bool) {
+    ) public virtual override returns (bool) {
         address caller = _msgSender();
         if (caller != sender && !isOperator(sender, caller)) {
             uint256 currentAllowance = allowance(sender, caller, id);
@@ -121,7 +121,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         address caller = _msgSender();
 
         if (from != address(0)) {
-            uint256 fromBalance = balanceOf(from, id);
+            uint256 fromBalance = _balances[id][from];
             if (fromBalance < amount) {
                 revert ERC6909InsufficientBalance(from, fromBalance, amount, id);
             }

From af6769f71d3c32b5a7d6d3aa6a01b6a71527623d Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Tue, 21 Jan 2025 11:24:47 +0100
Subject: [PATCH 33/47] updates

---
 contracts/interfaces/draft-IERC6909.sol       | 121 ++++++++++++++++-
 contracts/token/ERC6909/draft-ERC6909.sol     |  37 ++++--
 contracts/token/ERC6909/draft-IERC6909.sol    | 125 ------------------
 .../extensions/draft-ERC6909Metadata.sol      |  19 +--
 .../extensions/draft-ERC6909TokenSupply.sol   |   5 +-
 docs/modules/ROOT/nav.adoc                    |   2 +-
 test/token/ERC6909/ERC6909.behavior.js        |  45 ++++---
 .../extensions/ERC6909ContentURI.test.js      |   5 +-
 .../extensions/ERC6909Metadata.test.js        |  20 +--
 .../extensions/ERC6909TokenSupply.test.js     |   2 +-
 10 files changed, 187 insertions(+), 194 deletions(-)
 delete mode 100644 contracts/token/ERC6909/draft-IERC6909.sol

diff --git a/contracts/interfaces/draft-IERC6909.sol b/contracts/interfaces/draft-IERC6909.sol
index 0c05f81c944..12151e88656 100644
--- a/contracts/interfaces/draft-IERC6909.sol
+++ b/contracts/interfaces/draft-IERC6909.sol
@@ -1,4 +1,123 @@
 // SPDX-License-Identifier: MIT
+
 pragma solidity ^0.8.20;
 
-import {IERC6909, IERC6909Metadata, IERC6909ContentURI, IERC6909TokenSupply} from "../token/ERC6909/draft-IERC6909.sol";
+import {IERC165} from "../utils/introspection/IERC165.sol";
+
+/**
+ * @dev Required interface of an ERC-6909 compliant contract, as defined in the
+ * https://eips.ethereum.org/EIPS/eip-6909[ERC].
+ */
+interface IERC6909 is IERC165 {
+    /**
+     * @dev Emitted when the allowance of a `spender` for an `owner` is set for a token of type `id`.
+     * The new allowance is `amount`.
+     */
+    event Approval(address indexed owner, address indexed spender, uint256 indexed id, uint256 amount);
+
+    /**
+     * @dev Emitted when `owner` grants or revokes operator status for a `spender`.
+     */
+    event OperatorSet(address indexed owner, address indexed spender, bool approved);
+
+    /**
+     * @dev Emitted when `amount` tokens of type `id` are moved from `sender` to `receiver` initiated by `caller`.
+     */
+    event Transfer(
+        address caller,
+        address indexed sender,
+        address indexed receiver,
+        uint256 indexed id,
+        uint256 amount
+    );
+
+    /**
+     * @dev Returns the amount of tokens of type `id` owned by `owner`.
+     */
+    function balanceOf(address owner, uint256 id) external view returns (uint256);
+
+    /**
+     * @dev Returns the amount of tokens of type `id` that `spender` is allowed to spend on behalf of `owner`.
+     *
+     * NOTE: Does not include operator allowances.
+     */
+    function allowance(address owner, address spender, uint256 id) external view returns (uint256);
+
+    /**
+     * @dev Returns true if `spender` is set as an operator for `owner`.
+     */
+    function isOperator(address owner, address spender) external view returns (bool);
+
+    /**
+     * @dev Sets an approval to `spender` for `amount` tokens of type `id` from the caller's tokens.
+     *
+     * Must return true.
+     */
+    function approve(address spender, uint256 id, uint256 amount) external returns (bool);
+
+    /**
+     * @dev Grants or revokes unlimited transfer permission of any token id to `spender` for the caller's tokens.
+     *
+     * Must return true.
+     */
+    function setOperator(address spender, bool approved) external returns (bool);
+
+    /**
+     * @dev Transfers `amount` of token type `id` from the caller's account to `receiver`.
+     *
+     * Must return true.
+     */
+    function transfer(address receiver, uint256 id, uint256 amount) external returns (bool);
+
+    /**
+     * @dev Transfers `amount` of token type `id` from `sender` to `receiver`.
+     *
+     * Must return true.
+     */
+    function transferFrom(address sender, address receiver, uint256 id, uint256 amount) external returns (bool);
+}
+
+/**
+ * @dev Optional extension of {IERC6909} that adds metadata functions.
+ */
+interface IERC6909Metadata is IERC6909 {
+    /**
+     * @dev Returns the name of the token of type `id`.
+     */
+    function name(uint256 id) external view returns (string memory);
+
+    /**
+     * @dev Returns the ticker symbol of the token of type `id`.
+     */
+    function symbol(uint256 id) external view returns (string memory);
+
+    /**
+     * @dev Returns the number of decimals for the token of type `id`.
+     */
+    function decimals(uint256 id) external view returns (uint8);
+}
+
+/**
+ * @dev Optional extension of {IERC6909} that adds content URI functions.
+ */
+interface IERC6909ContentURI is IERC6909 {
+    /**
+     * @dev Returns URI for the contract.
+     */
+    function contractURI() external view returns (string memory);
+
+    /**
+     * @dev Returns the URI for the token of type `id`.
+     */
+    function tokenURI(uint256 id) external view returns (string memory);
+}
+
+/**
+ * @dev Optional extension of {IERC6909} that adds a token supply function.
+ */
+interface IERC6909TokenSupply is IERC6909 {
+    /**
+     * @dev Returns the total supply of the token of type `id`.
+     */
+    function totalSupply(uint256 id) external view returns (uint256);
+}
diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 667cfa4eeb1..695f64ee897 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -74,18 +74,9 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         uint256 amount
     ) public virtual override returns (bool) {
         address caller = _msgSender();
-        if (caller != sender && !isOperator(sender, caller)) {
-            uint256 currentAllowance = allowance(sender, caller, id);
-            if (currentAllowance != type(uint256).max) {
-                if (currentAllowance < amount) {
-                    revert ERC6909InsufficientAllowance(caller, currentAllowance, amount, id);
-                }
-                unchecked {
-                    _allowances[sender][caller][id] = currentAllowance - amount;
-                }
-            }
+        if (sender != caller && !isOperator(sender, caller)) {
+            _spendAllowance(sender, caller, id, amount);
         }
-
         _transfer(sender, receiver, id, amount);
         return true;
     }
@@ -126,7 +117,8 @@ contract ERC6909 is Context, ERC165, IERC6909 {
                 revert ERC6909InsufficientBalance(from, fromBalance, amount, id);
             }
             unchecked {
-                _balances[id][from] -= amount;
+                // Overflow not possible: amount <= fromBalance.
+                _balances[id][from] = fromBalance - amount;
             }
         }
         if (to != address(0)) {
@@ -165,4 +157,25 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         }
         _update(from, address(0), id, amount);
     }
+
+    /**
+     * @dev Updates `owner` s allowance for `spender` based on spent `value`.
+     *
+     * Does not update the allowance value in case of infinite allowance.
+     * Revert if not enough allowance is available.
+     *
+     * Does not emit an {Approval} event.
+     */
+    function _spendAllowance(address owner, address spender, uint256 id, uint256 amount) internal virtual {
+        uint256 currentAllowance = allowance(owner, spender, id);
+        // uint256 currentAllowance = allowance(owner, spender);
+        if (currentAllowance < type(uint256).max) {
+            if (currentAllowance < amount) {
+                revert ERC6909InsufficientAllowance(spender, currentAllowance, amount, id);
+            }
+            unchecked {
+                _allowances[owner][spender][id] = currentAllowance - amount;
+            }
+        }
+    }
 }
diff --git a/contracts/token/ERC6909/draft-IERC6909.sol b/contracts/token/ERC6909/draft-IERC6909.sol
deleted file mode 100644
index 33688dad540..00000000000
--- a/contracts/token/ERC6909/draft-IERC6909.sol
+++ /dev/null
@@ -1,125 +0,0 @@
-// SPDX-License-Identifier: MIT
-
-pragma solidity ^0.8.20;
-
-import {IERC165} from "../../utils/introspection/IERC165.sol";
-
-/**
- * @dev Required interface of an ERC-6909 compliant contract, as defined in the
- * https://eips.ethereum.org/EIPS/eip-6909[ERC].
- */
-interface IERC6909 is IERC165 {
-    /**
-     * @dev Emitted when the allowance of a `spender` for an `owner` is set for a token of type `id`.
-     * The new allowance is `amount`.
-     */
-    event Approval(address indexed owner, address indexed spender, uint256 indexed id, uint256 amount);
-
-    /**
-     * @dev Emitted when `owner` grants or revokes operator status for a `spender`.
-     */
-    event OperatorSet(address indexed owner, address indexed spender, bool approved);
-
-    /**
-     * @dev Emitted when `amount` tokens of type `id` are moved from `sender` to `receiver` initiated by `caller`.
-     */
-    event Transfer(
-        address caller,
-        address indexed sender,
-        address indexed receiver,
-        uint256 indexed id,
-        uint256 amount
-    );
-
-    /**
-     * @dev Returns the amount of tokens of type `id` owned by `owner`.
-     */
-    function balanceOf(address owner, uint256 id) external view returns (uint256);
-
-    /**
-     * @dev Returns the amount of tokens of type `id` that `spender` is allowed to spend on behalf of `owner`.
-     *
-     * NOTE: Does not include operator allowances.
-     */
-    function allowance(address owner, address spender, uint256 id) external view returns (uint256);
-
-    /**
-     * @dev Returns true if `spender` is set as an operator for `owner`.
-     */
-    function isOperator(address owner, address spender) external view returns (bool);
-
-    /**
-     * @dev Sets an approval to `spender` for `amount` tokens of type `id` from the caller's tokens.
-     *
-     * Must return true.
-     */
-    function approve(address spender, uint256 id, uint256 amount) external returns (bool);
-
-    /**
-     * @dev Grants or revokes unlimited transfer permission of any token id to `spender` for the caller's tokens.
-     *
-     * Must return true.
-     */
-    function setOperator(address spender, bool approved) external returns (bool);
-
-    /**
-     * @dev Transfers `amount` of token type `id` from the caller's account to `receiver`.
-     *
-     * Must return true.
-     */
-    function transfer(address receiver, uint256 id, uint256 amount) external returns (bool);
-
-    /**
-     * @dev Transfers `amount` of token type `id` from `sender` to `receiver`.
-     *
-     * Must return true.
-     */
-    function transferFrom(address sender, address receiver, uint256 id, uint256 amount) external returns (bool);
-}
-
-/**
- * @dev Optional extension of {IERC6909} that adds metadata functions.
- */
-interface IERC6909Metadata is IERC6909 {
-    /**
-     * @dev Returns the name of the token of type `id`.
-     */
-    function name(uint256 id) external view returns (string memory);
-
-    /**
-     * @dev Returns the ticker symbol of the token of type `id`.
-     */
-    function symbol(uint256 id) external view returns (string memory);
-
-    /**
-     * @dev Returns the number of decimals for the token of type `id`.
-     */
-    function decimals(uint256 id) external view returns (uint8);
-}
-
-/**
- * @dev Optional extension of {IERC6909} that adds content URI functions.
- */
-interface IERC6909ContentURI is IERC6909 {
-    /**
-     * @dev Returns URI for the contract.
-     */
-    function contractURI() external view returns (string memory);
-
-    /**
-     * @dev Returns the URI for the token of type `id`.
-     *
-     * NOTE: MUST replace occurrences of `{id}` in the returned URI string by the client.
-     */
-    function tokenURI(uint256 id) external view returns (string memory);
-}
-
-/**
- * @dev Optional extension of {IERC6909} that adds a token supply function.
- */
-interface IERC6909TokenSupply is IERC6909 {
-    /**
-     * @dev Returns the total supply of the token of type `id`.
-     */
-    function totalSupply(uint256 id) external view returns (uint256);
-}
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index d662043504f..857653db6e2 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -18,36 +18,29 @@ contract ERC6909Metadata is ERC6909, IERC6909Metadata {
     mapping(uint256 id => TokenMetadata) private _tokenMetadata;
 
     /// @inheritdoc IERC6909Metadata
-    function name(uint256 id) external view virtual override returns (string memory) {
+    function name(uint256 id) public view virtual override returns (string memory) {
         return _tokenMetadata[id].name;
     }
 
     /// @inheritdoc IERC6909Metadata
-    function symbol(uint256 id) external view virtual override returns (string memory) {
+    function symbol(uint256 id) public view virtual override returns (string memory) {
         return _tokenMetadata[id].symbol;
     }
 
     /// @inheritdoc IERC6909Metadata
-    function decimals(uint256 id) external view virtual override returns (uint8) {
+    function decimals(uint256 id) public view virtual override returns (uint8) {
         return _tokenMetadata[id].decimals;
     }
 
-    function _setName(uint256 id, string memory newName) internal {
+    function _setName(uint256 id, string memory newName) internal virtual {
         _tokenMetadata[id].name = newName;
     }
 
-    function _setSymbol(uint256 id, string memory newSymbol) internal {
+    function _setSymbol(uint256 id, string memory newSymbol) internal virtual {
         _tokenMetadata[id].symbol = newSymbol;
     }
 
-    function _setDecimals(uint256 id, uint8 newDecimals) internal {
+    function _setDecimals(uint256 id, uint8 newDecimals) internal virtual {
         _tokenMetadata[id].decimals = newDecimals;
     }
-
-    /**
-     * @dev Sets the metadata for a given token `id` to the provided `metadata` struct. Overwrites any previous metadata for this token id.
-     */
-    function _setTokenMetadata(uint256 id, TokenMetadata memory metadata) internal {
-        _tokenMetadata[id] = metadata;
-    }
 }
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol b/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
index d20cb7717b9..1ab14b71616 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
@@ -24,7 +24,10 @@ contract ERC6909TokenSupply is ERC6909, IERC6909TokenSupply {
         if (from == address(0)) {
             _totalSupplies[id] += amount;
         } else if (to == address(0)) {
-            _totalSupplies[id] -= amount;
+            unchecked {
+                // amount <= _balances[id][from] <= _totalSupplies[id]
+                _totalSupplies[id] -= amount;
+            }
         }
     }
 }
diff --git a/docs/modules/ROOT/nav.adoc b/docs/modules/ROOT/nav.adoc
index 59164ff9110..52f7e37b09d 100644
--- a/docs/modules/ROOT/nav.adoc
+++ b/docs/modules/ROOT/nav.adoc
@@ -12,8 +12,8 @@
 *** xref:erc20-supply.adoc[Creating Supply]
 ** xref:erc721.adoc[ERC-721]
 ** xref:erc1155.adoc[ERC-1155]
-** xref:erc6909.adoc[ERC-6909]
 ** xref:erc4626.adoc[ERC-4626]
+** xref:erc6909.adoc[ERC-6909]
 
 * xref:governance.adoc[Governance]
 
diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
index abbc8c78e98..d8989e243a1 100644
--- a/test/token/ERC6909/ERC6909.behavior.js
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -95,9 +95,9 @@ function shouldBehaveLikeERC6909() {
       });
 
       it('transfers to the zero address are blocked', async function () {
-        await expect(
-          this.token.connect(this.alice).transfer(ethers.ZeroAddress, firstTokenId, firstTokenAmount),
-        ).to.be.revertedWithCustomError(this.token, 'ERC6909InvalidReceiver');
+        await expect(this.token.connect(this.alice).transfer(ethers.ZeroAddress, firstTokenId, firstTokenAmount))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidReceiver')
+          .withArgs(ethers.ZeroAddress);
         await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(firstTokenAmount);
       });
 
@@ -112,7 +112,7 @@ function shouldBehaveLikeERC6909() {
           .to.emit(this.token, 'Transfer')
           .withArgs(this.alice, this.alice, this.bruce, firstTokenId, firstTokenAmount);
         await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(0);
-        return expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.equal(firstTokenAmount);
+        await expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.equal(firstTokenAmount);
       });
     });
 
@@ -123,33 +123,36 @@ function shouldBehaveLikeERC6909() {
       });
 
       it('transfer from self', async function () {
-        await this.token.connect(this.alice).transferFrom(this.alice, this.bruce, firstTokenId, firstTokenAmount);
+        await expect(
+          this.token.connect(this.alice).transferFrom(this.alice, this.bruce, firstTokenId, firstTokenAmount),
+        )
+          .to.emit(this.token, 'Transfer')
+          .withArgs(this.alice, this.alice, this.bruce, firstTokenId, firstTokenAmount);
         await expect(this.token.balanceOf(this.alice, firstTokenId)).to.eventually.equal(0);
         await expect(this.token.balanceOf(this.bruce, firstTokenId)).to.eventually.equal(firstTokenAmount);
       });
 
       describe('with approval', async function () {
         beforeEach(async function () {
-          await this.token.connect(this.alice).approve(this.operator, firstTokenId, firstTokenAmount - 1n);
-          this.tx = await this.token
-            .connect(this.operator)
-            .transferFrom(this.alice, this.bruce, firstTokenId, firstTokenAmount - 1n);
+          await this.token.connect(this.alice).approve(this.operator, firstTokenId, firstTokenAmount);
         });
 
         it('reverts when insufficient allowance', async function () {
-          await expect(this.token.connect(this.operator).transferFrom(this.alice, this.bruce, firstTokenId, 1))
+          await expect(
+            this.token.connect(this.operator).transferFrom(this.alice, this.bruce, firstTokenId, firstTokenAmount + 1n),
+          )
             .to.be.revertedWithCustomError(this.token, 'ERC6909InsufficientAllowance')
-            .withArgs(this.operator, 0, 1, firstTokenId);
+            .withArgs(this.operator, firstTokenAmount, firstTokenAmount + 1n, firstTokenId);
         });
 
-        it('should emit transfer event', async function () {
-          await expect(this.tx)
+        it('should emit transfer event and update approval (without an Approval event)', async function () {
+          await expect(
+            this.token.connect(this.operator).transferFrom(this.alice, this.bruce, firstTokenId, firstTokenAmount),
+          )
             .to.emit(this.token, 'Transfer')
-            .withArgs(this.operator, this.alice, this.bruce, firstTokenId, firstTokenAmount - 1n);
-        });
-
-        it('should update approval', async function () {
-          expect(this.token.allowance(this.alice, this.operator, firstTokenId)).to.eventually.equal(0);
+            .withArgs(this.operator, this.alice, this.bruce, firstTokenId, firstTokenAmount)
+            .to.not.emit(this.token, 'Approval');
+          await expect(this.token.allowance(this.alice, this.operator, firstTokenId)).to.eventually.equal(0);
         });
 
         it("shouldn't reduce allowance when infinite", async function () {
@@ -183,7 +186,11 @@ function shouldBehaveLikeERC6909() {
       it('operator transfer does not reduce allowance', async function () {
         // Also give allowance
         await this.token.connect(this.holder).approve(this.operator, firstTokenId, firstTokenAmount);
-        await this.token.connect(this.operator).transferFrom(this.holder, this.alice, firstTokenId, firstTokenAmount);
+        await expect(
+          this.token.connect(this.operator).transferFrom(this.holder, this.alice, firstTokenId, firstTokenAmount),
+        )
+          .to.emit(this.token, 'Transfer')
+          .withArgs(this.operator, this.holder, this.alice, firstTokenId, firstTokenAmount);
         await expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.equal(
           firstTokenAmount,
         );
diff --git a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
index 105da7a22d6..9a61fbafcf4 100644
--- a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
+++ b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
@@ -1,11 +1,10 @@
 const { ethers } = require('hardhat');
-const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 const { expect } = require('chai');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 
 async function fixture() {
-  const [operator, holder, ...otherAccounts] = await ethers.getSigners();
   const token = await ethers.deployContract('$ERC6909ContentURI');
-  return { token, operator, holder, otherAccounts };
+  return { token };
 }
 
 describe('ERC6909ContentURI', function () {
diff --git a/test/token/ERC6909/extensions/ERC6909Metadata.test.js b/test/token/ERC6909/extensions/ERC6909Metadata.test.js
index 270a0bcddc8..d9084f01853 100644
--- a/test/token/ERC6909/extensions/ERC6909Metadata.test.js
+++ b/test/token/ERC6909/extensions/ERC6909Metadata.test.js
@@ -1,11 +1,10 @@
 const { ethers } = require('hardhat');
-const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 const { expect } = require('chai');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 
 async function fixture() {
-  const [operator, holder, ...otherAccounts] = await ethers.getSigners();
   const token = await ethers.deployContract('$ERC6909Metadata');
-  return { token, operator, holder, otherAccounts };
+  return { token };
 }
 
 describe('ERC6909Metadata', function () {
@@ -25,11 +24,6 @@ describe('ERC6909Metadata', function () {
       // Only set for the specified token ID
       return expect(this.token.name(2n)).to.eventually.equal('');
     });
-
-    it('can be set by global setter', async function () {
-      await this.token.$_setTokenMetadata(1n, { name: 'My Token', symbol: '', decimals: '0' });
-      return expect(this.token.name(1n)).to.eventually.equal('My Token');
-    });
   });
 
   describe('symbol', function () {
@@ -44,11 +38,6 @@ describe('ERC6909Metadata', function () {
       // Only set for the specified token ID
       return expect(this.token.symbol(2n)).to.eventually.equal('');
     });
-
-    it('can be set by global setter', async function () {
-      await this.token.$_setTokenMetadata(1n, { name: '', symbol: 'MTK', decimals: '0' });
-      return expect(this.token.symbol(1n)).to.eventually.equal('MTK');
-    });
   });
 
   describe('decimals', function () {
@@ -63,10 +52,5 @@ describe('ERC6909Metadata', function () {
       // Only set for the specified token ID
       return expect(this.token.decimals(2n)).to.eventually.equal(0);
     });
-
-    it('can be set by global setter', async function () {
-      await this.token.$_setTokenMetadata(1n, { name: '', symbol: '', decimals: '18' });
-      return expect(this.token.decimals(1n)).to.eventually.equal(18);
-    });
   });
 });
diff --git a/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js b/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
index be2c990a2b6..8c6c19d372b 100644
--- a/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
+++ b/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
@@ -1,6 +1,6 @@
 const { ethers } = require('hardhat');
-const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 const { expect } = require('chai');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 
 const { shouldBehaveLikeERC6909 } = require('../ERC6909.behavior');
 

From d09f7fce14362dd44f14595135ac01abca1490ba Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Tue, 21 Jan 2025 11:34:47 +0100
Subject: [PATCH 34/47] fix total supply tracking during updates from 0 to 0

---
 .../extensions/draft-ERC6909TokenSupply.sol   |  3 +-
 .../extensions/ERC6909ContentURI.test.js      |  8 ++---
 .../extensions/ERC6909Metadata.test.js        | 10 +++---
 .../extensions/ERC6909TokenSupply.test.js     | 35 ++++++++++++++-----
 4 files changed, 38 insertions(+), 18 deletions(-)

diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol b/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
index 1ab14b71616..9c6f7a11ca0 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
@@ -23,7 +23,8 @@ contract ERC6909TokenSupply is ERC6909, IERC6909TokenSupply {
 
         if (from == address(0)) {
             _totalSupplies[id] += amount;
-        } else if (to == address(0)) {
+        }
+        if (to == address(0)) {
             unchecked {
                 // amount <= _balances[id][from] <= _totalSupplies[id]
                 _totalSupplies[id] -= amount;
diff --git a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
index 9a61fbafcf4..904c3a912af 100644
--- a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
+++ b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
@@ -14,12 +14,12 @@ describe('ERC6909ContentURI', function () {
 
   describe('contractURI', function () {
     it('is empty string be default', async function () {
-      return expect(this.token.contractURI()).to.eventually.equal('');
+      await expect(this.token.contractURI()).to.eventually.equal('');
     });
 
     it('is settable by internal setter', async function () {
       await this.token.$_setContractURI('https://example.com');
-      return expect(this.token.contractURI()).to.eventually.equal('https://example.com');
+      await expect(this.token.contractURI()).to.eventually.equal('https://example.com');
     });
 
     it('emits an event when set', async function () {
@@ -29,7 +29,7 @@ describe('ERC6909ContentURI', function () {
 
   describe('tokenURI', function () {
     it('is empty string be default', async function () {
-      return expect(this.token.tokenURI(1n)).to.eventually.equal('');
+      await expect(this.token.tokenURI(1n)).to.eventually.equal('');
     });
 
     it('can be set by dedicated setter', async function () {
@@ -37,7 +37,7 @@ describe('ERC6909ContentURI', function () {
       await expect(this.token.tokenURI(1n)).to.eventually.equal('https://example.com/1');
 
       // Only set for the specified token ID
-      return expect(this.token.tokenURI(2n)).to.eventually.equal('');
+      await expect(this.token.tokenURI(2n)).to.eventually.equal('');
     });
 
     it('emits an event when set', async function () {
diff --git a/test/token/ERC6909/extensions/ERC6909Metadata.test.js b/test/token/ERC6909/extensions/ERC6909Metadata.test.js
index d9084f01853..2d6fcc8c5d9 100644
--- a/test/token/ERC6909/extensions/ERC6909Metadata.test.js
+++ b/test/token/ERC6909/extensions/ERC6909Metadata.test.js
@@ -22,13 +22,13 @@ describe('ERC6909Metadata', function () {
       await expect(this.token.name(1n)).to.eventually.equal('My Token');
 
       // Only set for the specified token ID
-      return expect(this.token.name(2n)).to.eventually.equal('');
+      await expect(this.token.name(2n)).to.eventually.equal('');
     });
   });
 
   describe('symbol', function () {
     it('is empty string be default', async function () {
-      return expect(this.token.symbol(1n)).to.eventually.equal('');
+      await expect(this.token.symbol(1n)).to.eventually.equal('');
     });
 
     it('can be set by dedicated setter', async function () {
@@ -36,13 +36,13 @@ describe('ERC6909Metadata', function () {
       await expect(this.token.symbol(1n)).to.eventually.equal('MTK');
 
       // Only set for the specified token ID
-      return expect(this.token.symbol(2n)).to.eventually.equal('');
+      await expect(this.token.symbol(2n)).to.eventually.equal('');
     });
   });
 
   describe('decimals', function () {
     it('is 0 by default', async function () {
-      return expect(this.token.decimals(1n)).to.eventually.equal(0);
+      await expect(this.token.decimals(1n)).to.eventually.equal(0);
     });
 
     it('can be set by dedicated setter', async function () {
@@ -50,7 +50,7 @@ describe('ERC6909Metadata', function () {
       await expect(this.token.decimals(1n)).to.eventually.equal(18);
 
       // Only set for the specified token ID
-      return expect(this.token.decimals(2n)).to.eventually.equal(0);
+      await expect(this.token.decimals(2n)).to.eventually.equal(0);
     });
   });
 });
diff --git a/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js b/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
index 8c6c19d372b..df0c877a054 100644
--- a/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
+++ b/test/token/ERC6909/extensions/ERC6909TokenSupply.test.js
@@ -5,9 +5,9 @@ const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 const { shouldBehaveLikeERC6909 } = require('../ERC6909.behavior');
 
 async function fixture() {
-  const [operator, holder, ...otherAccounts] = await ethers.getSigners();
+  const [operator, holder, receiver, ...otherAccounts] = await ethers.getSigners();
   const token = await ethers.deployContract('$ERC6909TokenSupply');
-  return { token, operator, holder, otherAccounts };
+  return { token, operator, holder, receiver, otherAccounts };
 }
 
 describe('ERC6909TokenSupply', function () {
@@ -18,17 +18,36 @@ describe('ERC6909TokenSupply', function () {
   shouldBehaveLikeERC6909();
 
   describe('totalSupply', function () {
-    beforeEach(async function () {
-      await this.token.$_mint(this.holder, 1n, 1000n);
+    it('is zero before any mint', async function () {
+      await expect(this.token.totalSupply(1n)).to.eventually.be.equal(0n);
     });
 
     it('minting tokens increases the total supply', async function () {
-      return expect(this.token.totalSupply(1n)).to.eventually.be.equal(1000n);
+      await this.token.$_mint(this.receiver, 1n, 17n);
+      await expect(this.token.totalSupply(1n)).to.eventually.be.equal(17n);
     });
 
-    it('burning tokens decreases the total supply', async function () {
-      await this.token.$_burn(this.holder, 1n, 500n);
-      return expect(this.token.totalSupply(1n)).to.eventually.be.equal(500n);
+    describe('with tokens minted', function () {
+      const supply = 1000n;
+
+      beforeEach(async function () {
+        await this.token.$_mint(this.holder, 1n, supply);
+      });
+
+      it('burning tokens decreases the total supply', async function () {
+        await this.token.$_burn(this.holder, 1n, 17n);
+        await expect(this.token.totalSupply(1n)).to.eventually.be.equal(supply - 17n);
+      });
+
+      it('supply unaffected by transfers', async function () {
+        await this.token.$_transfer(this.holder, this.receiver, 1n, 42n);
+        await expect(this.token.totalSupply(1n)).to.eventually.be.equal(supply);
+      });
+
+      it('supply unaffected by no-op', async function () {
+        await this.token.$_update(ethers.ZeroAddress, ethers.ZeroAddress, 1n, 42n);
+        await expect(this.token.totalSupply(1n)).to.eventually.be.equal(supply);
+      });
     });
   });
 });

From 3219c9129b0a1c4963a4f6e97630278d5e43bcf9 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Tue, 21 Jan 2025 11:41:37 +0100
Subject: [PATCH 35/47] typo

---
 contracts/token/ERC6909/draft-ERC6909.sol | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 695f64ee897..237852d8898 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -159,7 +159,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     /**
-     * @dev Updates `owner` s allowance for `spender` based on spent `value`.
+     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
      *
      * Does not update the allowance value in case of infinite allowance.
      * Revert if not enough allowance is available.

From 37515f3a55808a7e5e271710a54d9a1102a00cac Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Tue, 21 Jan 2025 13:42:49 +0100
Subject: [PATCH 36/47] Update draft-ERC6909.sol

---
 contracts/token/ERC6909/draft-ERC6909.sol | 1 -
 1 file changed, 1 deletion(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 237852d8898..e86034eb546 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -168,7 +168,6 @@ contract ERC6909 is Context, ERC165, IERC6909 {
      */
     function _spendAllowance(address owner, address spender, uint256 id, uint256 amount) internal virtual {
         uint256 currentAllowance = allowance(owner, spender, id);
-        // uint256 currentAllowance = allowance(owner, spender);
         if (currentAllowance < type(uint256).max) {
             if (currentAllowance < amount) {
                 revert ERC6909InsufficientAllowance(spender, currentAllowance, amount, id);

From 2eff2056baf2f40e8711c36fa44a77065bfb96c7 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Tue, 21 Jan 2025 13:43:57 +0100
Subject: [PATCH 37/47] up

---
 test/token/ERC6909/ERC6909.test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/token/ERC6909/ERC6909.test.js b/test/token/ERC6909/ERC6909.test.js
index dedd7274556..a72f5245b94 100644
--- a/test/token/ERC6909/ERC6909.test.js
+++ b/test/token/ERC6909/ERC6909.test.js
@@ -1,8 +1,8 @@
 const { ethers } = require('hardhat');
+const { expect } = require('chai');
 const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
 
 const { shouldBehaveLikeERC6909 } = require('./ERC6909.behavior');
-const { expect } = require('chai');
 
 async function fixture() {
   const [operator, holder, ...otherAccounts] = await ethers.getSigners();

From e864372875cb94b19271f741d4a6a1393dc6844e Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Tue, 21 Jan 2025 12:32:08 -0500
Subject: [PATCH 38/47] reorder `_balances` mapping

---
 contracts/token/ERC6909/draft-ERC6909.sol | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index e86034eb546..95055926e5e 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -16,7 +16,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     error ERC6909InvalidReceiver(address receiver);
     error ERC6909InvalidSender(address sender);
 
-    mapping(uint256 id => mapping(address owner => uint256)) private _balances;
+    mapping(address owner => mapping(uint256 id => uint256)) private _balances;
 
     mapping(address owner => mapping(address operator => bool)) private _operatorApprovals;
 
@@ -29,7 +29,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
 
     /// @inheritdoc IERC6909
     function balanceOf(address owner, uint256 id) public view virtual override returns (uint256) {
-        return _balances[id][owner];
+        return _balances[owner][id];
     }
 
     /// @inheritdoc IERC6909
@@ -112,17 +112,17 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         address caller = _msgSender();
 
         if (from != address(0)) {
-            uint256 fromBalance = _balances[id][from];
+            uint256 fromBalance = _balances[from][id];
             if (fromBalance < amount) {
                 revert ERC6909InsufficientBalance(from, fromBalance, amount, id);
             }
             unchecked {
                 // Overflow not possible: amount <= fromBalance.
-                _balances[id][from] = fromBalance - amount;
+                _balances[from][id] = fromBalance - amount;
             }
         }
         if (to != address(0)) {
-            _balances[id][to] += amount;
+            _balances[to][id] += amount;
         }
 
         emit Transfer(caller, from, to, id, amount);

From fa66666352635030239bfd198095f7b9ace884f8 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Wed, 22 Jan 2025 17:08:37 -0500
Subject: [PATCH 39/47] Apply suggestions from code review
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Ernesto García <ernestognw@gmail.com>
---
 .../token/ERC6909/extensions/draft-ERC6909ContentURI.sol      | 4 ++--
 .../token/ERC6909/extensions/draft-ERC6909TokenSupply.sol     | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index 1547d7a4e29..8b3353aa29c 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -23,12 +23,12 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
     event MetadataUpdate(uint256 _tokenId);
 
     /// @inheritdoc IERC6909ContentURI
-    function contractURI() external view virtual override returns (string memory) {
+    function contractURI() public view virtual override returns (string memory) {
         return _contractURI;
     }
 
     /// @inheritdoc IERC6909ContentURI
-    function tokenURI(uint256 id) external view virtual override returns (string memory) {
+    function tokenURI(uint256 id) public view virtual override returns (string memory) {
         return _tokenURIs[id];
     }
 
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol b/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
index 9c6f7a11ca0..476935f8fe1 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909TokenSupply.sol
@@ -13,7 +13,7 @@ contract ERC6909TokenSupply is ERC6909, IERC6909TokenSupply {
     mapping(uint256 id => uint256) private _totalSupplies;
 
     /// @inheritdoc IERC6909TokenSupply
-    function totalSupply(uint256 id) external view virtual override returns (uint256) {
+    function totalSupply(uint256 id) public view virtual override returns (uint256) {
         return _totalSupplies[id];
     }
 

From 78d9d92feacc1796619f684730d496b88b306317 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 24 Jan 2025 11:34:44 -0500
Subject: [PATCH 40/47] update docs

---
 contracts/token/ERC6909/README.adoc | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/contracts/token/ERC6909/README.adoc b/contracts/token/ERC6909/README.adoc
index 48218f8692f..3fc9e1e5246 100644
--- a/contracts/token/ERC6909/README.adoc
+++ b/contracts/token/ERC6909/README.adoc
@@ -5,24 +5,21 @@ NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/
 
 This set of interfaces and contracts are all related to the https://eips.ethereum.org/EIPS/eip-6909[ERC-6909 Minimal Multi-Token Interface].
 
-The ERC consists of four interfaces which fulfill different roles, found here as {IERC6909}, {IERC6909Metadata}, {IERC6909ContentURI}, and {IERC6909TokenSupply}.
+The ERC consists of four interfaces which fulfill different roles--the interfaces are as follows:
+
+. {IERC6909}: Base interface for a vanilla ERC6909 token.
+. {IERC6909ContentURI}: Extends the base interface and adds content URI (contract and token level) functionality.
+. {IERC6909Metadata}: Extends the base interface and adds metadata functionality, which exposes a name, symbol, and decimals for each token id.
+. {IERC6909TokenSupply}: Extends the base interface and adds total supply functionality for each token id.
 
 Implementations are provided for each of the 4 interfaces defined in the ERC.
 
 == Core
 
-{{IERC6909}}
-
 {{ERC6909}}
 
 == Extensions
 
-{{IERC6909Metadata}}
-
-{{IERC6909ContentURI}}
-
-{{IERC6909TokenSupply}}
-
 {{ERC6909ContentURI}}
 
 {{ERC6909Metadata}}

From e81d3332505e3a0fe04357a45be8b5369569db9c Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Fri, 24 Jan 2025 12:38:26 -0500
Subject: [PATCH 41/47] add metadata events and use `URI` instead of
 `MetadataUpdate`

---
 .../extensions/draft-ERC6909ContentURI.sol    |  9 +++---
 .../extensions/draft-ERC6909Metadata.sol      | 30 +++++++++++++++++++
 .../extensions/ERC6909ContentURI.test.js      |  4 +--
 .../extensions/ERC6909Metadata.test.js        | 10 ++++---
 4 files changed, 42 insertions(+), 11 deletions(-)

diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index 8b3353aa29c..2c8a85c84ac 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -17,10 +17,9 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
      */
     event ContractURIUpdated();
 
-    /**
-     * @dev See {IERC4906-MetadataUpdate}. This contract does not inherit {IERC4906} as it requires {IERC721}.
-     */
-    event MetadataUpdate(uint256 _tokenId);
+    /// @dev See {IERC1155-URI}
+
+    event URI(string value, uint256 indexed id);
 
     /// @inheritdoc IERC6909ContentURI
     function contractURI() public view virtual override returns (string memory) {
@@ -41,6 +40,6 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
     function _setTokenURI(uint256 id, string memory newTokenURI) internal {
         _tokenURIs[id] = newTokenURI;
 
-        emit MetadataUpdate(id);
+        emit URI(newTokenURI, id);
     }
 }
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index 857653db6e2..352b0e0edea 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -17,6 +17,15 @@ contract ERC6909Metadata is ERC6909, IERC6909Metadata {
 
     mapping(uint256 id => TokenMetadata) private _tokenMetadata;
 
+    /// The name of the token of type `id` was updated to `newName`.
+    event ERC6909NameUpdated(uint256 indexed id, string newName);
+
+    /// @dev The symbol for the token of type `id` was updated to `newSymbol`.
+    event ERC6909SymbolUpdated(uint256 indexed id, string newSymbol);
+
+    /// @dev The decimals value for token of type `id` was updated to `newDecimals`.
+    event ERC6909DecimalsUpdated(uint256 indexed id, uint8 newDecimals);
+
     /// @inheritdoc IERC6909Metadata
     function name(uint256 id) public view virtual override returns (string memory) {
         return _tokenMetadata[id].name;
@@ -32,15 +41,36 @@ contract ERC6909Metadata is ERC6909, IERC6909Metadata {
         return _tokenMetadata[id].decimals;
     }
 
+    /**
+     * @dev Sets the `name` for a given token of type `id`.
+     *
+     * Emits an {ERC6909NameUpdated} event.
+     */
     function _setName(uint256 id, string memory newName) internal virtual {
         _tokenMetadata[id].name = newName;
+
+        emit ERC6909NameUpdated(id, newName);
     }
 
+    /**
+     * @dev Sets the `symbol` for a given token of type `id`.
+     *
+     * Emits an {ERC6909SymbolUpdated} event.
+     */
     function _setSymbol(uint256 id, string memory newSymbol) internal virtual {
         _tokenMetadata[id].symbol = newSymbol;
+
+        emit ERC6909SymbolUpdated(id, newSymbol);
     }
 
+    /**
+     * @dev Sets the `decimals` for a given token of type `id`.
+     *
+     * Emits an {ERC6909DecimalsUpdated} event.
+     */
     function _setDecimals(uint256 id, uint8 newDecimals) internal virtual {
         _tokenMetadata[id].decimals = newDecimals;
+
+        emit ERC6909DecimalsUpdated(id, newDecimals);
     }
 }
diff --git a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
index 904c3a912af..3597eb78e8a 100644
--- a/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
+++ b/test/token/ERC6909/extensions/ERC6909ContentURI.test.js
@@ -42,8 +42,8 @@ describe('ERC6909ContentURI', function () {
 
     it('emits an event when set', async function () {
       await expect(this.token.$_setTokenURI(1n, 'https://example.com/1'))
-        .to.emit(this.token, 'MetadataUpdate')
-        .withArgs(1n);
+        .to.emit(this.token, 'URI')
+        .withArgs('https://example.com/1', 1n);
     });
   });
 });
diff --git a/test/token/ERC6909/extensions/ERC6909Metadata.test.js b/test/token/ERC6909/extensions/ERC6909Metadata.test.js
index 2d6fcc8c5d9..e6d3dd9f32d 100644
--- a/test/token/ERC6909/extensions/ERC6909Metadata.test.js
+++ b/test/token/ERC6909/extensions/ERC6909Metadata.test.js
@@ -14,11 +14,13 @@ describe('ERC6909Metadata', function () {
 
   describe('name', function () {
     it('is empty string be default', async function () {
-      return expect(this.token.name(1n)).to.eventually.equal('');
+      await expect(this.token.name(1n)).to.eventually.equal('');
     });
 
     it('can be set by dedicated setter', async function () {
-      await this.token.$_setName(1n, 'My Token');
+      await expect(this.token.$_setName(1n, 'My Token'))
+        .to.emit(this.token, 'ERC6909NameUpdated')
+        .withArgs(1n, 'My Token');
       await expect(this.token.name(1n)).to.eventually.equal('My Token');
 
       // Only set for the specified token ID
@@ -32,7 +34,7 @@ describe('ERC6909Metadata', function () {
     });
 
     it('can be set by dedicated setter', async function () {
-      await this.token.$_setSymbol(1n, 'MTK');
+      await expect(this.token.$_setSymbol(1n, 'MTK')).to.emit(this.token, 'ERC6909SymbolUpdated').withArgs(1n, 'MTK');
       await expect(this.token.symbol(1n)).to.eventually.equal('MTK');
 
       // Only set for the specified token ID
@@ -46,7 +48,7 @@ describe('ERC6909Metadata', function () {
     });
 
     it('can be set by dedicated setter', async function () {
-      await this.token.$_setDecimals(1n, 18);
+      await expect(this.token.$_setDecimals(1n, 18)).to.emit(this.token, 'ERC6909DecimalsUpdated').withArgs(1n, 18);
       await expect(this.token.decimals(1n)).to.eventually.equal(18);
 
       // Only set for the specified token ID

From b4eb0bc5904ebbe4d1041c0c1945af857bb204db Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Sun, 26 Jan 2025 15:11:33 -0500
Subject: [PATCH 42/47] formatting

---
 contracts/token/ERC6909/draft-ERC6909.sol              | 10 +++++-----
 .../ERC6909/extensions/draft-ERC6909ContentURI.sol     |  9 +++------
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 95055926e5e..e702a440fa7 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -11,17 +11,17 @@ import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
  * See https://eips.ethereum.org/EIPS/eip-6909
  */
 contract ERC6909 is Context, ERC165, IERC6909 {
-    error ERC6909InsufficientBalance(address sender, uint256 balance, uint256 needed, uint256 id);
-    error ERC6909InsufficientAllowance(address spender, uint256 allowance, uint256 needed, uint256 id);
-    error ERC6909InvalidReceiver(address receiver);
-    error ERC6909InvalidSender(address sender);
-
     mapping(address owner => mapping(uint256 id => uint256)) private _balances;
 
     mapping(address owner => mapping(address operator => bool)) private _operatorApprovals;
 
     mapping(address owner => mapping(address spender => mapping(uint256 id => uint256))) private _allowances;
 
+    error ERC6909InsufficientBalance(address sender, uint256 balance, uint256 needed, uint256 id);
+    error ERC6909InsufficientAllowance(address spender, uint256 allowance, uint256 needed, uint256 id);
+    error ERC6909InvalidReceiver(address receiver);
+    error ERC6909InvalidSender(address sender);
+
     /// @inheritdoc IERC165
     function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
         return interfaceId == type(IERC6909).interfaceId || super.supportsInterface(interfaceId);
diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index 2c8a85c84ac..bca24c0332a 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -12,13 +12,10 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
     string private _contractURI;
     mapping(uint256 id => string) private _tokenURIs;
 
-    /**
-     * @dev Event emitted when the contract URI is changed. See https://eips.ethereum.org/EIPS/eip-7572[ERC-7572] for details.
-     */
+    /// @dev Event emitted when the contract URI is changed. See https://eips.ethereum.org/EIPS/eip-7572[ERC-7572] for details.
     event ContractURIUpdated();
 
     /// @dev See {IERC1155-URI}
-
     event URI(string value, uint256 indexed id);
 
     /// @inheritdoc IERC6909ContentURI
@@ -31,13 +28,13 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
         return _tokenURIs[id];
     }
 
-    function _setContractURI(string memory newContractURI) internal {
+    function _setContractURI(string memory newContractURI) internal virtual {
         _contractURI = newContractURI;
 
         emit ContractURIUpdated();
     }
 
-    function _setTokenURI(uint256 id, string memory newTokenURI) internal {
+    function _setTokenURI(uint256 id, string memory newTokenURI) internal virtual {
         _tokenURIs[id] = newTokenURI;
 
         emit URI(newTokenURI, id);

From a9bb0637bde8008e085364b467155f5998435369 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Sun, 26 Jan 2025 15:16:48 -0500
Subject: [PATCH 43/47] add missing dev tag

---
 contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
index 352b0e0edea..4132863863a 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909Metadata.sol
@@ -17,7 +17,7 @@ contract ERC6909Metadata is ERC6909, IERC6909Metadata {
 
     mapping(uint256 id => TokenMetadata) private _tokenMetadata;
 
-    /// The name of the token of type `id` was updated to `newName`.
+    /// @dev The name of the token of type `id` was updated to `newName`.
     event ERC6909NameUpdated(uint256 indexed id, string newName);
 
     /// @dev The symbol for the token of type `id` was updated to `newSymbol`.

From 267df513c7a5ee39db00cdd80003ccacf5a704e9 Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Sun, 26 Jan 2025 22:14:09 -0500
Subject: [PATCH 44/47] add docs

---
 .../ERC6909/extensions/draft-ERC6909ContentURI.sol     | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
index bca24c0332a..8839947936d 100644
--- a/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
+++ b/contracts/token/ERC6909/extensions/draft-ERC6909ContentURI.sol
@@ -28,12 +28,22 @@ contract ERC6909ContentURI is ERC6909, IERC6909ContentURI {
         return _tokenURIs[id];
     }
 
+    /**
+     * @dev Sets the {contractURI} for the contract.
+     *
+     * Emits a {ContractURIUpdated} event.
+     */
     function _setContractURI(string memory newContractURI) internal virtual {
         _contractURI = newContractURI;
 
         emit ContractURIUpdated();
     }
 
+    /**
+     * @dev Sets the {tokenURI} for a given token of type `id`.
+     *
+     * Emits a {URI} event.
+     */
     function _setTokenURI(uint256 id, string memory newTokenURI) internal virtual {
         _tokenURIs[id] = newTokenURI;
 

From de3d5dc71dc723371312d78b0fbc065f4665c614 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Mon, 27 Jan 2025 14:01:10 +0100
Subject: [PATCH 45/47] add missing internal setters

---
 contracts/token/ERC6909/draft-ERC6909.sol | 92 +++++++++++++++++------
 1 file changed, 68 insertions(+), 24 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index e702a440fa7..6ba51dac17a 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -19,8 +19,10 @@ contract ERC6909 is Context, ERC165, IERC6909 {
 
     error ERC6909InsufficientBalance(address sender, uint256 balance, uint256 needed, uint256 id);
     error ERC6909InsufficientAllowance(address spender, uint256 allowance, uint256 needed, uint256 id);
+    error ERC6909InvalidApprover(address approver);
     error ERC6909InvalidReceiver(address receiver);
     error ERC6909InvalidSender(address sender);
+    error ERC6909InvalidSpender(address spender);
 
     /// @inheritdoc IERC165
     function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
@@ -44,19 +46,13 @@ contract ERC6909 is Context, ERC165, IERC6909 {
 
     /// @inheritdoc IERC6909
     function approve(address spender, uint256 id, uint256 amount) public virtual override returns (bool) {
-        address caller = _msgSender();
-        _allowances[caller][spender][id] = amount;
-
-        emit Approval(caller, spender, id, amount);
+        _approve(_msgSender(), spender, id, amount);
         return true;
     }
 
     /// @inheritdoc IERC6909
     function setOperator(address spender, bool approved) public virtual override returns (bool) {
-        address caller = _msgSender();
-        _operatorApprovals[caller][spender] = approved;
-
-        emit OperatorSet(caller, spender, approved);
+        _setOperator(_msgSender(), spender, approved);
         return true;
     }
 
@@ -81,6 +77,21 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         return true;
     }
 
+    /**
+     * @dev Creates `amount` of token `id` and assigns them to `account`, by transferring it from address(0).
+     * Relies on the `_update` mechanism
+     *
+     * Emits a {Transfer} event with `from` set to the zero address.
+     *
+     * NOTE: This function is not virtual, {_update} should be overridden instead.
+     */
+    function _mint(address to, uint256 id, uint256 amount) internal {
+        if (to == address(0)) {
+            revert ERC6909InvalidReceiver(address(0));
+        }
+        _update(address(0), to, id, amount);
+    }
+
     /**
      * @dev Moves `amount` of token `id` from `from` to `to` without checking for approvals.
      *
@@ -101,6 +112,21 @@ contract ERC6909 is Context, ERC165, IERC6909 {
         _update(from, to, id, amount);
     }
 
+    /**
+     * @dev Destroys a `amount` of token `id` from `account`.
+     * Relies on the `_update` mechanism.
+     *
+     * Emits a {Transfer} event with `to` set to the zero address.
+     *
+     * NOTE: This function is not virtual, {_update} should be overridden instead
+     */
+    function _burn(address from, uint256 id, uint256 amount) internal {
+        if (from == address(0)) {
+            revert ERC6909InvalidSender(address(0));
+        }
+        _update(from, address(0), id, amount);
+    }
+
     /**
      * @dev Transfers `amount` of token `id` from `from` to `to`, or alternatively mints (or burns) if `from`
      * (or `to`) is the zero address. All customizations to transfers, mints, and burns should be done by overriding
@@ -129,33 +155,51 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     /**
-     * @dev Creates `amount` of token `id` and assigns them to `account`, by transferring it from address(0).
-     * Relies on the `_update` mechanism
+     * @dev Sets `amount` as the allowance of `spender` over the `owner` s `id` tokens.
      *
-     * Emits a {Transfer} event with `from` set to the zero address.
+     * This internal function is equivalent to `approve`, and can be used to e.g. set automatic allowances for certain
+     * subsystems, etc.
      *
-     * NOTE: This function is not virtual, {_update} should be overridden instead.
+     * Emits an {Approval} event.
+     *
+     * Requirements:
+     *
+     * - `owner` cannot be the zero address.
+     * - `spender` cannot be the zero address.
      */
-    function _mint(address to, uint256 id, uint256 amount) internal {
-        if (to == address(0)) {
-            revert ERC6909InvalidReceiver(address(0));
+    function _approve(address owner, address spender, uint256 id, uint256 amount) internal virtual {
+        if (owner == address(0)) {
+            revert ERC6909InvalidApprover(address(0));
         }
-        _update(address(0), to, id, amount);
+        if (spender == address(0)) {
+            revert ERC6909InvalidSpender(address(0));
+        }
+        _allowances[owner][spender][id] = amount;
+        emit Approval(owner, spender, id, amount);
     }
 
     /**
-     * @dev Destroys a `amount` of token `id` from `account`.
-     * Relies on the `_update` mechanism.
+     * @dev Approve `spender` to operate on all of `owner` tokens
      *
-     * Emits a {Transfer} event with `to` set to the zero address.
+     * This internal function is equivalent to `setOperator`, and can be used to e.g. set automatic allowances for
+     * certain subsystems, etc.
      *
-     * NOTE: This function is not virtual, {_update} should be overridden instead
+     * Emits an {OperatorSet} event.
+     *
+     * Requirements:
+     *
+     * - `owner` cannot be the zero address.
+     * - `spender` cannot be the zero address.
      */
-    function _burn(address from, uint256 id, uint256 amount) internal {
-        if (from == address(0)) {
-            revert ERC6909InvalidSender(address(0));
+    function _setOperator(address owner, address spender, bool approved) internal virtual {
+        if (owner == address(0)) {
+            revert ERC6909InvalidApprover(address(0));
         }
-        _update(from, address(0), id, amount);
+        if (spender == address(0)) {
+            revert ERC6909InvalidSpender(address(0));
+        }
+        _operatorApprovals[owner][spender] = approved;
+        emit OperatorSet(owner, spender, approved);
     }
 
     /**

From 8f239eabb29d15fcef39dad1958b9584bfb9103f Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Mon, 27 Jan 2025 16:55:12 +0100
Subject: [PATCH 46/47] testing

---
 test/token/ERC6909/ERC6909.behavior.js | 39 +++++++++++++++-----------
 test/token/ERC6909/ERC6909.test.js     | 32 ++++++++++++++++++---
 2 files changed, 50 insertions(+), 21 deletions(-)

diff --git a/test/token/ERC6909/ERC6909.behavior.js b/test/token/ERC6909/ERC6909.behavior.js
index d8989e243a1..bfac00b8f46 100644
--- a/test/token/ERC6909/ERC6909.behavior.js
+++ b/test/token/ERC6909/ERC6909.behavior.js
@@ -40,16 +40,14 @@ function shouldBehaveLikeERC6909() {
     });
 
     describe('setOperator', function () {
-      beforeEach(async function () {
-        this.tx = await this.token.connect(this.holder).setOperator(this.operator, true);
-      });
-
-      it('emits an an OperatorSet event', async function () {
-        await expect(this.tx).to.emit(this.token, 'OperatorSet').withArgs(this.holder, this.operator, true);
-      });
+      it('emits an an OperatorSet event and updated the value', async function () {
+        await expect(this.token.connect(this.holder).setOperator(this.operator, true))
+          .to.emit(this.token, 'OperatorSet')
+          .withArgs(this.holder, this.operator, true);
 
-      it('should be reflected in isOperator call', async function () {
+        // operator for holder
         await expect(this.token.isOperator(this.holder, this.operator)).to.eventually.be.true;
+
         // not operator for other account
         await expect(this.token.isOperator(this.alice, this.operator)).to.eventually.be.false;
       });
@@ -59,24 +57,25 @@ function shouldBehaveLikeERC6909() {
           .to.emit(this.token, 'OperatorSet')
           .withArgs(this.holder, this.operator, false);
       });
-    });
 
-    describe('approve', function () {
-      beforeEach(async function () {
-        this.tx = await this.token.connect(this.holder).approve(this.operator, firstTokenId, firstTokenAmount);
+      it('cannot set address(0) as an operator', async function () {
+        await expect(this.token.setOperator(ethers.ZeroAddress, true))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidSpender')
+          .withArgs(ethers.ZeroAddress);
       });
+    });
 
-      it('emits an Approval event', async function () {
-        await expect(this.tx)
+    describe('approve', function () {
+      it('emits an Approval event and updates allowance', async function () {
+        await expect(this.token.connect(this.holder).approve(this.operator, firstTokenId, firstTokenAmount))
           .to.emit(this.token, 'Approval')
           .withArgs(this.holder, this.operator, firstTokenId, firstTokenAmount);
-      });
 
-      it('is reflected in allowance', async function () {
+        // approved
         await expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.be.equal(
           firstTokenAmount,
         );
-        // not operator for other account
+        // other account is not approved
         await expect(this.token.allowance(this.alice, this.operator, firstTokenId)).to.eventually.be.equal(0);
       });
 
@@ -86,6 +85,12 @@ function shouldBehaveLikeERC6909() {
           .withArgs(this.holder, this.operator, firstTokenId, 0);
         await expect(this.token.allowance(this.holder, this.operator, firstTokenId)).to.eventually.be.equal(0);
       });
+
+      it('cannot give allowance to address(0)', async function () {
+        await expect(this.token.connect(this.holder).approve(ethers.ZeroAddress, firstTokenId, firstTokenAmount))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidSpender')
+          .withArgs(ethers.ZeroAddress);
+      });
     });
 
     describe('transfer', function () {
diff --git a/test/token/ERC6909/ERC6909.test.js b/test/token/ERC6909/ERC6909.test.js
index a72f5245b94..7c635b49193 100644
--- a/test/token/ERC6909/ERC6909.test.js
+++ b/test/token/ERC6909/ERC6909.test.js
@@ -46,6 +46,20 @@ describe('ERC6909', function () {
       });
     });
 
+    describe('_transfer', function () {
+      it('reverts when transferring from the zero address', async function () {
+        await expect(this.token.$_transfer(ethers.ZeroAddress, this.holder, 1n, 1n))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidSender')
+          .withArgs(ethers.ZeroAddress);
+      });
+
+      it('reverts when transferring to the zero address', async function () {
+        await expect(this.token.$_transfer(this.holder, ethers.ZeroAddress, 1n, 1n))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidReceiver')
+          .withArgs(ethers.ZeroAddress);
+      });
+    });
+
     describe('_burn', function () {
       it('reverts with a zero from address', async function () {
         await expect(this.token.$_burn(ethers.ZeroAddress, tokenId, burnValue))
@@ -71,10 +85,20 @@ describe('ERC6909', function () {
       });
     });
 
-    it('reverts when transferring from the zero address', async function () {
-      await expect(this.token.$_transfer(ethers.ZeroAddress, this.holder, 1n, 1n))
-        .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidSender')
-        .withArgs(ethers.ZeroAddress);
+    describe('_approve', function () {
+      it('reverts when the owner is the zero address', async function () {
+        await expect(this.token.$_approve(ethers.ZeroAddress, this.recipient, 1n, 1n))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidApprover')
+          .withArgs(ethers.ZeroAddress);
+      });
+    });
+
+    describe('_setOperator', function () {
+      it('reverts when the owner is the zero address', async function () {
+        await expect(this.token.$_setOperator(ethers.ZeroAddress, this.operator, true))
+          .to.be.revertedWithCustomError(this.token, 'ERC6909InvalidApprover')
+          .withArgs(ethers.ZeroAddress);
+      });
     });
   });
 });

From d1297b08f32e8844371743eea6175db3a324edcd Mon Sep 17 00:00:00 2001
From: Arr00 <13561405+arr00@users.noreply.github.com>
Date: Mon, 27 Jan 2025 10:57:14 -0500
Subject: [PATCH 47/47] fix apostrophe

---
 contracts/token/ERC6909/draft-ERC6909.sol | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/contracts/token/ERC6909/draft-ERC6909.sol b/contracts/token/ERC6909/draft-ERC6909.sol
index 6ba51dac17a..e821d4b3b22 100644
--- a/contracts/token/ERC6909/draft-ERC6909.sol
+++ b/contracts/token/ERC6909/draft-ERC6909.sol
@@ -155,7 +155,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     /**
-     * @dev Sets `amount` as the allowance of `spender` over the `owner` s `id` tokens.
+     * @dev Sets `amount` as the allowance of `spender` over the `owner`'s `id` tokens.
      *
      * This internal function is equivalent to `approve`, and can be used to e.g. set automatic allowances for certain
      * subsystems, etc.
@@ -179,7 +179,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     /**
-     * @dev Approve `spender` to operate on all of `owner` tokens
+     * @dev Approve `spender` to operate on all of `owner`'s tokens
      *
      * This internal function is equivalent to `setOperator`, and can be used to e.g. set automatic allowances for
      * certain subsystems, etc.
@@ -203,7 +203,7 @@ contract ERC6909 is Context, ERC165, IERC6909 {
     }
 
     /**
-     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
+     * @dev Updates `owner`'s allowance for `spender` based on spent `amount`.
      *
      * Does not update the allowance value in case of infinite allowance.
      * Revert if not enough allowance is available.