From e6015e2bb509f740f955a17ffd6d0c7d49115ee7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ji=C5=99=C3=AD=20Brabec?= <brabeji@gmail.com>
Date: Sun, 1 Sep 2024 21:45:40 +0200
Subject: [PATCH 1/2] POC of typed extension views for arbitrary list of
 extensions.

---
 .../__tests__/ext.spec.ts                     | 40 +++++++++++++++++++
 src/json-crdt/model/Model.ts                  | 23 +++++++----
 src/json-crdt/nodes/types.ts                  | 11 ++++-
 src/json-crdt/schema/types.ts                 | 23 ++++++++---
 4 files changed, 83 insertions(+), 14 deletions(-)
 create mode 100644 src/json-crdt-extensions/__tests__/ext.spec.ts

diff --git a/src/json-crdt-extensions/__tests__/ext.spec.ts b/src/json-crdt-extensions/__tests__/ext.spec.ts
new file mode 100644
index 0000000000..35f451e6c9
--- /dev/null
+++ b/src/json-crdt-extensions/__tests__/ext.spec.ts
@@ -0,0 +1,40 @@
+import {s} from '../../json-crdt-patch';
+import {Extension} from '../../json-crdt/extensions/Extension';
+import {ExtNode} from '../../json-crdt/extensions/ExtNode';
+import {ExtApi} from '../../json-crdt/extensions/types';
+import * as ext from '../../json-crdt-extensions/ext';
+import {NodeApi} from '../../json-crdt/model/api/nodes';
+import {Model} from '../../json-crdt/model/Model';
+import {ObjNode} from '../../json-crdt/nodes';
+
+export type FileView = {type: 'File'; content: {type: 'Content'}};
+class FileNode extends ExtNode<ObjNode, FileView> {
+  public readonly extId = 101;
+
+  public name(): string {
+    return 'File' as const;
+  }
+
+  public view(): FileView {
+    return {type: 'File', content: {type: 'Content'}};
+  }
+}
+class FileApi extends NodeApi<FileNode> implements ExtApi<FileNode> {}
+export const File = new Extension(101, 'File', FileNode, FileApi, () =>
+  s.obj({type: s.con('File'), content: s.map({})}),
+);
+
+describe('Extensions', () => {
+  test('type inference', () => {
+    const schema = s.obj({
+      field1: File.new(),
+      field2: ext.cnt.new(1),
+      field3: s.con('a'),
+      field4: ext.mval.new(1),
+    });
+    const model = Model.create(schema, 1, {extensions: [File, ext.cnt, ext.mval]});
+    const v = model.view();
+    // now typed correctly
+    type ModelView = typeof v;
+  });
+});
diff --git a/src/json-crdt/model/Model.ts b/src/json-crdt/model/Model.ts
index d07406c178..b74615e2f8 100644
--- a/src/json-crdt/model/Model.ts
+++ b/src/json-crdt/model/Model.ts
@@ -15,6 +15,7 @@ import type {JsonNode, JsonNodeView} from '../nodes/types';
 import type {Printable} from 'tree-dump/lib/types';
 import type {NodeBuilder} from '../../json-crdt-patch';
 import type {NodeApi} from './api/nodes';
+import {Extension} from '../extensions/Extension';
 
 export const UNDEFINED = new ConNode(ORIGIN, undefined);
 
@@ -147,17 +148,21 @@ export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
    *        session ID generated by {@link Model.sid}.
    * @returns A strictly typed model.
    */
-  public static readonly create = <S extends NodeBuilder>(
+  public static readonly create = <S extends NodeBuilder, E extends Extension<any, any, any, any, any, any>[] = []>(
     schema?: S,
     sidOrClock: clock.ClockVector | number = Model.sid(),
-  ): Model<SchemaToJsonNode<S>> => {
+    options?: {extensions?: E},
+  ): Model<SchemaToJsonNode<S, E>> => {
     const cl =
       typeof sidOrClock === 'number'
         ? sidOrClock === SESSION.SERVER
           ? new clock.ServerClockVector(SESSION.SERVER, 1)
           : new clock.ClockVector(sidOrClock, 1)
         : sidOrClock;
-    const model = new Model<SchemaToJsonNode<S>>(cl);
+    const model = new Model<SchemaToJsonNode<S, E>>(cl);
+    for (const extension of options?.extensions ?? []) {
+      model.ext.register(extension);
+    }
     if (schema) model.setSchema(schema, true);
     return model;
   };
@@ -186,12 +191,16 @@ export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
    * @param sid Session ID to set for the model.
    * @returns An instance of a model.
    */
-  public static readonly load = <S extends NodeBuilder>(
+  public static readonly load = <S extends NodeBuilder, E extends Extension<any, any, any, any, any, any>[]>(
     data: Uint8Array,
     sid?: number,
     schema?: S,
-  ): Model<SchemaToJsonNode<S>> => {
-    const model = decoder.decode(data) as unknown as Model<SchemaToJsonNode<S>>;
+    options?: {extensions?: E},
+  ): Model<SchemaToJsonNode<S, E>> => {
+    const model = decoder.decode(data) as unknown as Model<SchemaToJsonNode<S, E>>;
+    for (const extension of options?.extensions ?? []) {
+      model.ext.register(extension);
+    }
     if (schema) model.setSchema(schema, true);
     if (typeof sid === 'number') model.setSid(sid);
     return model;
@@ -537,7 +546,7 @@ export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
    *            session.
    * @returns Strictly typed model.
    */
-  public setSchema<S extends NodeBuilder>(schema: S, useGlobalSession: boolean = true): Model<SchemaToJsonNode<S>> {
+  public setSchema<S extends NodeBuilder>(schema: S, useGlobalSession: boolean = true): Model<SchemaToJsonNode<S, []>> {
     const c = this.clock;
     const isNewDocument = c.time === 1;
     if (isNewDocument) {
diff --git a/src/json-crdt/nodes/types.ts b/src/json-crdt/nodes/types.ts
index fb56284524..f3902f97eb 100644
--- a/src/json-crdt/nodes/types.ts
+++ b/src/json-crdt/nodes/types.ts
@@ -1,4 +1,7 @@
 import type {Identifiable} from '../../json-crdt-patch/types';
+import {ExtNode} from '../extensions/ExtNode';
+import {ExtensionVecData} from '../schema/types';
+import {VecNode} from './vec/VecNode';
 
 /**
  * Each JsonNode represents a structural unit of a JSON document. It is like an
@@ -44,4 +47,10 @@ export interface JsonNode<View = unknown> extends Identifiable {
   api: undefined | unknown; // JsonNodeApi<this>;
 }
 
-export type JsonNodeView<N> = N extends JsonNode<infer V> ? V : {[K in keyof N]: JsonNodeView<N[K]>};
+export type JsonNodeView<N> = N extends ExtNode<any, infer V>
+  ? V
+  : N extends VecNode<ExtensionVecData<infer N2>>
+  ? JsonNodeView<N2>
+  : N extends JsonNode<infer V>
+  ? V
+  : {[K in keyof N]: JsonNodeView<N[K]>};
diff --git a/src/json-crdt/schema/types.ts b/src/json-crdt/schema/types.ts
index bf2df60013..b1782b390f 100644
--- a/src/json-crdt/schema/types.ts
+++ b/src/json-crdt/schema/types.ts
@@ -4,29 +4,40 @@ import type {PeritextNode, QuillDeltaNode} from '../../json-crdt-extensions';
 import type {nodes as builder} from '../../json-crdt-patch';
 import type {ExtNode} from '../extensions/ExtNode';
 import type * as nodes from '../nodes';
+import {Extension} from '../extensions/Extension';
 
 // prettier-ignore
-export type SchemaToJsonNode<S> = S extends builder.str<infer T>
+export type SchemaToJsonNode<S, Extensions extends Extension<number, any, any, any, any>[] = []> = S extends builder.str<infer T>
   ? nodes.StrNode<T>
   : S extends builder.bin
     ? nodes.BinNode
     : S extends builder.con<infer T>
       ? nodes.ConNode<T>
       : S extends builder.val<infer T>
-        ? nodes.ValNode<SchemaToJsonNode<T>>
+        ? nodes.ValNode<SchemaToJsonNode<T,Extensions>>
         : S extends builder.vec<infer T>
-          ? nodes.VecNode<{[K in keyof T]: SchemaToJsonNode<T[K]>}>
+          ? nodes.VecNode<{[K in keyof T]: SchemaToJsonNode<T[K],Extensions>}>
           : S extends builder.obj<infer T>
-            ? nodes.ObjNode<{[K in keyof T]: SchemaToJsonNode<T[K]>}>
+            ? nodes.ObjNode<{[K in keyof T]: SchemaToJsonNode<T[K],Extensions>}>
             : S extends builder.arr<infer T>
-              ? nodes.ArrNode<SchemaToJsonNode<T>>
+              ? nodes.ArrNode<SchemaToJsonNode<T,Extensions>>
               : S extends builder.ext<ExtensionId.peritext, any>
                 ? nodes.VecNode<ExtensionVecData<PeritextNode>>
                 : S extends builder.ext<ExtensionId.quill, any>
                   ? nodes.VecNode<ExtensionVecData<QuillDeltaNode>>
                   : S extends builder.ext<ExtensionId.mval, any>
                     ? nodes.VecNode<ExtensionVecData<MvalNode>>
-                    : nodes.JsonNode;
+                    : S extends builder.ext<infer ExtId, any>
+                      ? Extensions extends (infer ExtsUnion)[] 
+                          ? nodes.VecNode<
+                              ExtensionVecData<
+                                Extract<ExtsUnion, { readonly id: ExtId }> extends Extension<any, any, infer M, any, any, any>
+                                  ? M extends ExtNode<any, any>?M:never
+                                  : never
+                              >
+                            >
+                          : never
+                      : nodes.JsonNode;
 
 export type ExtensionVecData<EDataNode extends ExtNode<any, any>> = {__BRAND__: 'ExtVecData'} & [
   header: nodes.ConNode<Uint8Array>,

From c4e9d57f8112897f57d1fee902f3a7070d049de0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ji=C5=99=C3=AD=20Brabec?= <brabeji@gmail.com>
Date: Thu, 5 Sep 2024 19:18:19 +0200
Subject: [PATCH 2/2] POC of typed node apis for arbitrary list of extensions.

---
 .../__tests__/ext.spec.ts                     |  6 ++-
 src/json-crdt/model/Model.ts                  | 22 ++++----
 src/json-crdt/model/api/ModelApi.ts           |  9 ++--
 src/json-crdt/model/api/nodes.ts              | 39 +++++++++-----
 src/json-crdt/model/api/types.ts              | 51 +++++++++++--------
 src/json-crdt/schema/types.ts                 | 10 ++--
 6 files changed, 81 insertions(+), 56 deletions(-)

diff --git a/src/json-crdt-extensions/__tests__/ext.spec.ts b/src/json-crdt-extensions/__tests__/ext.spec.ts
index 35f451e6c9..78818522c4 100644
--- a/src/json-crdt-extensions/__tests__/ext.spec.ts
+++ b/src/json-crdt-extensions/__tests__/ext.spec.ts
@@ -19,7 +19,9 @@ class FileNode extends ExtNode<ObjNode, FileView> {
     return {type: 'File', content: {type: 'Content'}};
   }
 }
-class FileApi extends NodeApi<FileNode> implements ExtApi<FileNode> {}
+class FileApi extends NodeApi<FileNode> implements ExtApi<FileNode> {
+  rename() {}
+}
 export const File = new Extension(101, 'File', FileNode, FileApi, () =>
   s.obj({type: s.con('File'), content: s.map({})}),
 );
@@ -34,7 +36,9 @@ describe('Extensions', () => {
     });
     const model = Model.create(schema, 1, {extensions: [File, ext.cnt, ext.mval]});
     const v = model.view();
+    const f1 = model.api.node.get('field1');
     // now typed correctly
     type ModelView = typeof v;
+    type NodeApi = typeof f1;
   });
 });
diff --git a/src/json-crdt/model/Model.ts b/src/json-crdt/model/Model.ts
index b74615e2f8..1853cae5e6 100644
--- a/src/json-crdt/model/Model.ts
+++ b/src/json-crdt/model/Model.ts
@@ -23,7 +23,9 @@ export const UNDEFINED = new ConNode(ORIGIN, undefined);
  * In instance of Model class represents the underlying data structure,
  * i.e. model, of the JSON CRDT document.
  */
-export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
+export class Model<N extends JsonNode = JsonNode<any>, Exts extends Extension<number, any, any, any, any>[] = []>
+  implements Printable
+{
   /**
    * Generates a random session ID. Use this method to generate a session ID
    * for a new user. Store the session ID in the user's browser or device once
@@ -152,14 +154,14 @@ export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
     schema?: S,
     sidOrClock: clock.ClockVector | number = Model.sid(),
     options?: {extensions?: E},
-  ): Model<SchemaToJsonNode<S, E>> => {
+  ): Model<SchemaToJsonNode<S, E>, E> => {
     const cl =
       typeof sidOrClock === 'number'
         ? sidOrClock === SESSION.SERVER
           ? new clock.ServerClockVector(SESSION.SERVER, 1)
           : new clock.ClockVector(sidOrClock, 1)
         : sidOrClock;
-    const model = new Model<SchemaToJsonNode<S, E>>(cl);
+    const model = new Model<SchemaToJsonNode<S, E>, E>(cl);
     for (const extension of options?.extensions ?? []) {
       model.ext.register(extension);
     }
@@ -196,8 +198,8 @@ export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
     sid?: number,
     schema?: S,
     options?: {extensions?: E},
-  ): Model<SchemaToJsonNode<S, E>> => {
-    const model = decoder.decode(data) as unknown as Model<SchemaToJsonNode<S, E>>;
+  ): Model<SchemaToJsonNode<S, E>,E> => {
+    const model = decoder.decode(data) as unknown as Model<SchemaToJsonNode<S, E>,E>;
     for (const extension of options?.extensions ?? []) {
       model.ext.register(extension);
     }
@@ -261,13 +263,13 @@ export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
   }
 
   /** @ignore */
-  private _api?: ModelApi<N>;
+  private _api?: ModelApi<N, Exts>;
 
   /**
    * API for applying local changes to the current document.
    */
-  public get api(): ModelApi<N> {
-    if (!this._api) this._api = new ModelApi<N>(this);
+  public get api(): ModelApi<N, Exts> {
+    if (!this._api) this._api = new ModelApi<N, Exts>(this);
     return this._api;
   }
 
@@ -476,7 +478,7 @@ export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
    *
    * @returns A copy of this model with the same session ID.
    */
-  public clone(): Model<N> {
+  public clone(): Model<N, Exts> {
     return this.fork(this.clock.sid);
   }
 
@@ -493,7 +495,7 @@ export class Model<N extends JsonNode = JsonNode<any>> implements Printable {
   /**
    * Resets the model to equivalent state of another model.
    */
-  public reset(to: Model<N>): void {
+  public reset(to: Model<N, Exts>): void {
     this.onbeforereset?.();
     const index = this.index;
     this.index = new AvlMap<clock.ITimestampStruct, JsonNode>(clock.compare);
diff --git a/src/json-crdt/model/api/ModelApi.ts b/src/json-crdt/model/api/ModelApi.ts
index e92d658244..43045aeb84 100644
--- a/src/json-crdt/model/api/ModelApi.ts
+++ b/src/json-crdt/model/api/ModelApi.ts
@@ -7,7 +7,8 @@ import {SyncStore} from '../../../util/events/sync-store';
 import {MergeFanOut, MicrotaskBufferFanOut} from './fanout';
 import {ExtNode} from '../../extensions/ExtNode';
 import type {Model} from '../Model';
-import type {JsonNode, JsonNodeView} from '../../nodes';
+import type {JsonNode, JsonNodeView, RootNode} from '../../nodes';
+import {Extension} from '../../extensions/Extension';
 
 /**
  * Local changes API for a JSON CRDT model. This class is the main entry point
@@ -15,7 +16,9 @@ import type {JsonNode, JsonNodeView} from '../../nodes';
  *
  * @category Local API
  */
-export class ModelApi<N extends JsonNode = JsonNode> implements SyncStore<JsonNodeView<N>> {
+export class ModelApi<N extends JsonNode = JsonNode, Extensions extends Extension<number, any, any, any, any>[] = []>
+  implements SyncStore<JsonNodeView<N>>
+{
   /**
    * Patch builder for the local changes.
    */
@@ -99,7 +102,7 @@ export class ModelApi<N extends JsonNode = JsonNode> implements SyncStore<JsonNo
    * Local changes API for the root node.
    */
   public get r() {
-    return new ValApi(this.model.root, this);
+    return new ValApi<RootNode<N>, Extensions>(this.model.root, this);
   }
 
   /** @ignore */
diff --git a/src/json-crdt/model/api/nodes.ts b/src/json-crdt/model/api/nodes.ts
index f64dbb22ed..65eaa46159 100644
--- a/src/json-crdt/model/api/nodes.ts
+++ b/src/json-crdt/model/api/nodes.ts
@@ -21,11 +21,10 @@ export type ApiPath = string | number | Path | void;
  *
  * @category Local API
  */
-export class NodeApi<N extends JsonNode = JsonNode> implements Printable {
-  constructor(
-    public node: N,
-    public readonly api: ModelApi<any>,
-  ) {}
+export class NodeApi<N extends JsonNode = JsonNode, Extensions extends Extension<number, any, any, any, any>[] = []>
+  implements Printable
+{
+  constructor(public node: N, public readonly api: ModelApi<any>) {}
 
   /** @ignore */
   private ev: undefined | NodeEvents<N> = undefined;
@@ -122,7 +121,7 @@ export class NodeApi<N extends JsonNode = JsonNode> implements Printable {
    * @param ext Extension of the node
    * @returns API of the extension
    */
-  public asExt(): JsonNodeApi<VecNodeExtensionData<N>> | ExtApi<any> | undefined;
+  public asExt(): JsonNodeApi<VecNodeExtensionData<N>, Extensions> | ExtApi<any> | undefined;
   public asExt<EN extends ExtNode<any, any>, EApi extends ExtApi<EN>>(
     ext: Extension<any, any, EN, EApi, any, any>,
   ): EApi;
@@ -206,12 +205,15 @@ export class ConApi<N extends ConNode<any> = ConNode<any>> extends NodeApi<N> {
  *
  * @category Local API
  */
-export class ValApi<N extends ValNode<any> = ValNode<any>> extends NodeApi<N> {
+export class ValApi<
+  N extends ValNode<any> = ValNode<any>,
+  Extensions extends Extension<number, any, any, any, any>[] = [],
+> extends NodeApi<N> {
   /**
    * Get API instance of the inner node.
    * @returns Inner node API.
    */
-  public get(): JsonNodeApi<N extends ValNode<infer T> ? T : JsonNode> {
+  public get(): JsonNodeApi<N extends ValNode<infer T> ? T : JsonNode, Extensions> {
     return this.in() as any;
   }
 
@@ -254,14 +256,17 @@ type UnVecNode<N> = N extends VecNode<infer T> ? T : never;
  *
  * @category Local API
  */
-export class VecApi<N extends VecNode<any> = VecNode<any>> extends NodeApi<N> {
+export class VecApi<
+  N extends VecNode<any> = VecNode<any>,
+  Extensions extends Extension<number, any, any, any, any>[] = [],
+> extends NodeApi<N> {
   /**
    * Get API instance of a child node.
    *
    * @param key Object key to get.
    * @returns A specified child node API.
    */
-  public get<K extends keyof UnVecNode<N>>(key: K): JsonNodeApi<UnVecNode<N>[K]> {
+  public get<K extends keyof UnVecNode<N>>(key: K): JsonNodeApi<UnVecNode<N>[K], Extensions> {
     return this.in(key as string) as any;
   }
 
@@ -326,14 +331,17 @@ type UnObjNode<N> = N extends ObjNode<infer T> ? T : never;
  *
  * @category Local API
  */
-export class ObjApi<N extends ObjNode<any> = ObjNode<any>> extends NodeApi<N> {
+export class ObjApi<
+  N extends ObjNode<any> = ObjNode<any>,
+  Extensions extends Extension<number, any, any, any, any>[] = [],
+> extends NodeApi<N> {
   /**
    * Get API instance of a child node.
    *
    * @param key Object key to get.
    * @returns A specified child node API.
    */
-  public get<K extends keyof UnObjNode<N>>(key: K): JsonNodeApi<UnObjNode<N>[K]> {
+  public get<K extends keyof UnObjNode<N>>(key: K): JsonNodeApi<UnObjNode<N>[K], Extensions> {
     return this.in(key as string) as any;
   }
 
@@ -560,14 +568,17 @@ type UnArrNode<N> = N extends ArrNode<infer T> ? T : never;
  *
  * @category Local API
  */
-export class ArrApi<N extends ArrNode<any> = ArrNode<any>> extends NodeApi<N> {
+export class ArrApi<
+  N extends ArrNode<any> = ArrNode<any>,
+  Extensions extends Extension<number, any, any, any, any>[] = [],
+> extends NodeApi<N> {
   /**
    * Get API instance of a child node.
    *
    * @param index Index of the element to get.
    * @returns Child node API for the element at the given index.
    */
-  public get(index: number): JsonNodeApi<UnArrNode<N>> {
+  public get(index: number): JsonNodeApi<UnArrNode<N>, Extensions> {
     return this.in(index) as any;
   }
 
diff --git a/src/json-crdt/model/api/types.ts b/src/json-crdt/model/api/types.ts
index 78d4b283d4..e9727ae2be 100644
--- a/src/json-crdt/model/api/types.ts
+++ b/src/json-crdt/model/api/types.ts
@@ -1,26 +1,35 @@
 import type {PeritextNode, PeritextApi, QuillDeltaNode, QuillDeltaApi} from '../../../json-crdt-extensions';
+import { Extension } from '../../extensions/Extension';
+import { ExtNode } from '../../extensions/ExtNode';
 import type * as types from '../../nodes';
 import type * as nodes from './nodes';
 
 // prettier-ignore
-export type JsonNodeApi<N> = N extends types.ConNode<any>
-  ? nodes.ConApi<N>
-  : N extends types.RootNode<any>
-    ? nodes.ValApi<N>
-    : N extends types.ValNode<any>
-      ? nodes.ValApi<N>
-      : N extends types.StrNode
-        ? nodes.StrApi
-        : N extends types.BinNode
-          ? nodes.BinApi
-          : N extends types.ArrNode<any>
-            ? nodes.ArrApi<N>
-            : N extends types.ObjNode<any>
-              ? nodes.ObjApi<N>
-              : N extends types.VecNode<any>
-                ? nodes.VecApi<N>
-                : N extends PeritextNode
-                  ? PeritextApi
-                  : N extends QuillDeltaNode
-                    ? QuillDeltaApi
-                    : never;
+export type JsonNodeApi<N, Extensions extends Extension<number, any, any, any, any>[]> = 
+N extends ExtNode<any>
+	? Extensions extends (infer ExtsUnion)[] 
+				? Extract<ExtsUnion, { readonly id: N['extId'] }> extends Extension<number, any, any, infer Api, any, any>
+							? Api
+							: never
+				: never
+	:	N extends types.ConNode<any>
+		? nodes.ConApi<N>
+		: N extends types.RootNode<any>
+			? nodes.ValApi<N>
+			: N extends types.ValNode<any>
+				? nodes.ValApi<N, Extensions>
+				: N extends types.StrNode
+					? nodes.StrApi
+					: N extends types.BinNode
+						? nodes.BinApi
+						: N extends types.ArrNode<any>
+							? nodes.ArrApi<N, Extensions>
+							: N extends types.ObjNode<any>
+								? nodes.ObjApi<N, Extensions>
+								: N extends types.VecNode<any>
+									? nodes.VecApi<N, Extensions>
+									: N extends PeritextNode
+										? PeritextApi
+										: N extends QuillDeltaNode
+											? QuillDeltaApi
+											: never;
diff --git a/src/json-crdt/schema/types.ts b/src/json-crdt/schema/types.ts
index b1782b390f..3b20951bd1 100644
--- a/src/json-crdt/schema/types.ts
+++ b/src/json-crdt/schema/types.ts
@@ -29,13 +29,9 @@ export type SchemaToJsonNode<S, Extensions extends Extension<number, any, any, a
                     ? nodes.VecNode<ExtensionVecData<MvalNode>>
                     : S extends builder.ext<infer ExtId, any>
                       ? Extensions extends (infer ExtsUnion)[] 
-                          ? nodes.VecNode<
-                              ExtensionVecData<
-                                Extract<ExtsUnion, { readonly id: ExtId }> extends Extension<any, any, infer M, any, any, any>
-                                  ? M extends ExtNode<any, any>?M:never
-                                  : never
-                              >
-                            >
+                          ? Extract<ExtsUnion, { readonly id: ExtId }> extends Extension<any, any, infer M, any, any, any>
+                                ? M
+                                : never
                           : never
                       : nodes.JsonNode;