rust-analyzer does not return LSP suggestions when enabled via nix-direnv

[antoineco]

nix-direnv 3.0.6

I use the following Flake to describe a standard development environment for Rust:

flake.nix

{
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-24.11";
    rust-overlay.url = "https://flakehub.com/f/oxalica/rust-overlay/0.1";
  };

  outputs =
    {
      self,
      nixpkgs,
      rust-overlay,
    }:
    let
      allSystems = [
        "x86_64-linux"
        "aarch64-darwin"
      ];

      forAllSystems =
        f:
        nixpkgs.lib.genAttrs allSystems (
          system:
          f {
            pkgs = import nixpkgs {
              inherit system;
              overlays = [
                rust-overlay.overlays.default
              ];
            };
          }
        );
    in
    {
      devShells = forAllSystems (
        { pkgs }:
        {
          rust =
            with pkgs;
            mkShell {
              name = "rust";
              packages =
                let
                  rust-stable-custom = rust-bin.stable.latest.default.override {
                    extensions = [
                      "rust-analyzer"
                      "rust-src"
                    ];
                  };
                in
                [ rust-stable-custom ];
            };
        }
      );
    };
}

If I use nix develop '.#rust' -c zsh and open my editor (Neovim), the LSP integration with rust-analyzer works flawlessly (diagnostics from clippy, completions, ...). ✅

If I instead create an .envrc with use flake ${HOME}/myflake#rust, code completions do not trigger in rust-analyzer, although the exact same Nix store directory for Rust tools is present in my PATH in both cases. ❌

This can be replicated in any Cargo project, such as the one bootstrapped by cargo init.

Simply illustated:

nix develop

nix direnv (no LSP completions)

The only noticeable difference from the LSP progress message is that, in the nix-direnv case, progress stops at:

rust-analyzer [Roots Scanned] 15/15

Whereas while using nix develop it continues after that point with:

rust-analyzer [Fetching] metadata
rust-analyzer [Loading proc-macros]
rust-analyzer [Building CrateGraph]
rust-analyzer [Indexing] 22/22 (myproject)

I haven't noticed any issue in any similar setup, using devShells for Go, Nix and Bash mainly.

I intend to investigate further the differences between the two environment (nix develop vs nix-direnv), but wanted to create an issue anyway with the observed symptoms.

[antoineco]

Closing as upstream issue:

• rust-analyzer.files.excludeDirs is (still) not working rust-lang/rust-analyzer#14734 (comment)