unresolved extern crate on Nixos

[StealthyKamereon]

rust-analyzer version: rust-analyzer 1.80.0-nightly (d84b903 2024-05-19)

rustc version: rustc 1.80.0-nightly (d84b90375 2024-05-19)

editor or extension: NeoVim configured with lspconfig

relevant settings:

rust_analyzer = {
  cargo = {
    features = "all",
  },
  rustc = { source = "discover" },
},

repository link (if public, optional): rustc_plugin example

steps to reproduce:
Clone the example from https://github.com/cognitive-engineering-lab/rustc_plugin/ and change the crate:

git clone https://github.com/cognitive-engineering-lab/rustc_plugin/
cd example/print-all-items
sed -i 's;rustc_plugin = { path = "../.." };rustc_plugin = "=0.10.0-nightly-2024-05-20"' Cargo.toml

Create a shell.nix with the following content:

{ nixpkgs ? import <nixpkgs> { }}:

let
  rustOverlay = builtins.fetchTarball "https://github.com/oxalica/rust-overlay/archive/master.tar.gz";
  pinnedPkgs = nixpkgs.fetchFromGitHub {
    owner  = "NixOS";
    repo   = "nixpkgs";
    rev    = "b3fcfcfabd01b947a1e4f36622bbffa3985bdac6";
    sha256 = "0va68ddkrqb6j349rsbkjhdq7m243kg9njcqhnx9p2sbrcl2g5l8";
  };
  pkgs = import pinnedPkgs {
    overlays = [ (import rustOverlay) ];
  };
  rust_pkg = pkgs.rust-bin.nightly."2024-05-20".default.override {
    extensions = ["rust-src" "rustc" "rustc-dev" "llvm-tools" "rust-analyzer" "cargo"];
  };
in
  pkgs.mkShell {
    buildInputs = with pkgs; [
      (
        rust_pkg
      )
      openssl
      pkg-config
      eza
      fd
    ];

    RUST_BACKTRACE = 1;
    RUST_SRC_PATH = "${rust_pkg}/lib/rustlib/src/rust/library";
  }

Enter the shell:

nix-shell

Launch RA:

rust-analyzer diagnostics .

You will have the following errors:

processing crate: print_all_items_driver, module: /print-all-items/src/bin/print-all-items-driver.rs
processing crate: cargo_print_all_items, module: /print-all-items/src/bin/cargo-print-all-items.rs
processing crate: print_all_items, module: /print-all-items/src/lib.rs
Diagnostic { code: RustcHardError("unresolved-extern-crate"), message: "unresolved extern crate", range: FileRange { file_id: FileId(11), range: 98..124 }, severity: Error, unused: false, experimental: false, fixes: None, main_node: Some(InFileWrapper { file_id: FileId(11), value: SyntaxNodePtr { kind: EXTERN_CRATE, range: 98..124 } }) }
Diagnostic { code: RustcHardError("unresolved-extern-crate"), message: "unresolved extern crate", range: FileRange { file_id: FileId(11), range: 125..154 }, severity: Error, unused: false, experimental: false, fixes: None, main_node: Some(InFileWrapper { file_id: FileId(11), value: SyntaxNodePtr { kind: EXTERN_CRATE, range: 125..154 } }) }
Diagnostic { code: RustcHardError("unresolved-extern-crate"), message: "unresolved extern crate", range: FileRange { file_id: FileId(11), range: 155..181 }, severity: Error, unused: false, experimental: false, fixes: None, main_node: Some(InFileWrapper { file_id: FileId(11), value: SyntaxNodePtr { kind: EXTERN_CRATE, range: 155..181 } }) }
Diagnostic { code: RustcHardError("unresolved-extern-crate"), message: "unresolved extern crate", range: FileRange { file_id: FileId(11), range: 182..209 }, severity: Error, unused: false, experimental: false, fixes: None, main_node: Some(InFileWrapper { file_id: FileId(11), value: SyntaxNodePtr { kind: EXTERN_CRATE, range: 182..209 } }) }

diagnostic scan complete

Error: diagnostic error detected

Stack backtrace:
   0: <anyhow::Error>::msg::<&str>
   1: std::sys_common::backtrace::__rust_begin_short_backtrace::<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>
   2: <<std::thread::Builder>::spawn_unchecked_<<stdx::thread::Builder>::spawn<<rust_analyzer::cli::flags::Diagnostics>::run::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#0}, core::result::Result<(), anyhow::Error>>::{closure#2} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
   3: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/d84b9037541f45dc2c52a41d723265af211c0497/library/alloc/src/boxed.rs:2022:9
   4: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/d84b9037541f45dc2c52a41d723265af211c0497/library/alloc/src/boxed.rs:2022:9
   5: std::sys::pal::unix::thread::Thread::new::thread_start
             at /rustc/d84b9037541f45dc2c52a41d723265af211c0497/library/std/src/sys/pal/unix/thread.rs:108:17
   6: start_thread
   7: __GI___clone3

See cognitive-engineering-lab/rustc_plugin#26 for additional information.

[StealthyKamereon]

Anybody willing to help me on this ?

[Multirious]

Encountered the same problem and I found out that:

1. I guess that rust-analyzer with rust-analyzer.rustc.source = "discover" won't find files inside the nix store so I tried to explicitly set the file location.
2. I tried /nix/store/ydmh9f2s01bdgzz9f8y6a20mbkrchh13-rust-default-1.85.0-nightly-2024-12-16/lib/rustlib/rustc-src/rust/compiler/rustc/Cargo.toml for rust-analyzer.rustc.source
3. rust-analyzer continue to error but this time it log out that some certain command failed.
4. I tried running that command manually and found out that it's saying the file does not exists which I figured that rust-analzyer do not read symlink
5. I readlinked the Cargo.toml and use that value for rust-analyzer.rustc.source and the command found the file!
6. ...except there's no Cargo.lock and rust-analyzer is trying to write the file to the nix store ...Unfortunately a deadend I guess

[Multirious]

I found out that in the part that reads rustc_source doesn't canonicalize the path in any way. Is this intended? .canonicalize is also seems like it's explicitly not implemented too.

[Multirious]

I think we also need #10792

[Multirious]

For those looking for workaround, there is cognitive-engineering-lab/rustc_plugin#26 (comment) by @StealthyKamereon

For those who can't wait a fix, I found a dirty workaround.

Make a directory in your project and create a auxiliary nix store by copying the rust package :

# Set the RUST_PKG with the shell.nix. For example, my RUST_PKG contains the following:

export RUST_PKG=/nix/store/v0769idpz76l6b3xff8ps98bcsy5ymjb-rust-default-1.80.0-nightly-2024-05-20



nix copy --to /<project-dir>/local-store $RUST_PKG --no-check-sigs

This will take care of copying all the necessary packages.

Then simply enable writing in the local store:

chmod u+w -R /<project-dir>/local-store

You then need to tell your lsp where your sysroot is. For example, I have these settings for vscode:

{

    "rust-analyzer.server.path": "/<project-dir>/local-store/nix/store/v0769idpz76l6b3xff8ps98bcsy5ymjb-rust-default-1.80.0-nightly-2024-05-20/bin/rust-analyzer",

    "rust-analyzer.cargo.sysroot": "/<project-dir>/local-store/nix/store/v0769idpz76l6b3xff8ps98bcsy5ymjb-rust-default-1.80.0-nightly-2024-05-20/",

    "rust-analyzer.rustc.source": "discover"

}

Just to make my life easier, I've made this script:

#!/usr/bin/env bash

# local_nix directory is <current dir>/.local-nix
local_nix="$(dirname "$(readlink -f "$0")")/.local-nix"

# remake if local nix directory do not exists or the current copy do not match $RUST_PKG
if [ ! -d "$local_nix" ]; then
  should_remake="true"
elif [ "$(cat "$local_nix/origin_rust_pkg")" != "$RUST_PKG" ]; then
  should_remake="true"

  # Clear current copy
  echo "Clearing $local_nix"
  rm -rf "$local_nix"
else
  should_remake="false"
fi

if [ "$should_remake" = "true" ]; then
  echo "Making $local_nix"

  # copy nix
  nix copy --to "$local_nix" $RUST_PKG --no-check-sigs

  # Make writable
  chmod u+w -R "$local_nix"

  # Save original path to file
  echo "$RUST_PKG" > "$local_nix/origin_rust_pkg"
fi

[StealthyKamereon]

Yes, thanks for reposting the workaround here :)
I literally spent months try to find it so I guess I was a bit lazy and just posted on one of the three issues. Sorry for that.

For anyone coming here, see this workaround.

[Multirious]

Thanks for making the workaround anyways! I have no idea know how long I'm going to take without the works you've done. Mega time saver.