LALRPOP language server

lalrpop-lsp provides Language Server Protocol support for LALRPOP, an LR(1) parser generator for Rust. The language server communicates over standard input/output and is shared by the VS Code and Zed integrations in this repository.

Repository layout

• src/ contains the editor-independent Rust language server.
• grammars/lalrpop/ contains the patched Tree-sitter grammar used by the Zed integration.
• grammars/lalrpop-rust/ contains the pinned Rust-expression dialect used for LALRPOP action blocks in Zed.
• editors/vscode/ contains the VS Code extension, TextMate grammar, and TypeScript client.
• editors/zed/ contains the Zed WASM adapter and Tree-sitter language files.

Install the language server

Both editors can run a lalrpop-lsp executable already available on PATH:

cargo install --git https://github.com/LighghtEeloo/lalrpop-lsp.git --locked

VS Code

Install LALRPOP Language Server from the VS Code Marketplace. If lalrpop-lsp is not available on PATH, the extension offers to install it with Cargo on first use.

To use a specific server build, set lalrpop-language-server.server.path in VS Code settings.

Zed

Until the extension is published in Zed's extension registry, install it as a development extension:

1. Install lalrpop-lsp with the command above.
2. Run zed: install dev extension from Zed's command palette.
3. Select the editors/zed directory from this checkout.

If the Zed process cannot see the server on PATH, set an explicit binary path in Zed's settings.json:

{
  "lsp": {
    "lalrpop-lsp": {
      "binary": {
        "path": "/absolute/path/to/lalrpop-lsp"
      }
    }
  }
}

Features

• Go to definition
• Find references
• Document occurrence highlighting
• Hover information
• Document symbols
• Syntax error diagnostics
• Navigation and semantic highlighting retained across incomplete edits
• Syntax highlighting in both editors
• Semantic highlighting for nonterminal and macro definitions and references

Development

Build and test the language server from the repository root:

cargo test

Build the VS Code extension:

cd editors/vscode
pnpm install
pnpm run compile

You can then open the repository in VS Code and run the Launch VS Code Client debug configuration.

Check the Zed adapter with:

cargo check --manifest-path editors/zed/Cargo.toml

Validate the vendored Tree-sitter grammar with:

cd grammars/lalrpop
pnpm dlx tree-sitter-cli@0.25.10 test

Validate the injected Rust action grammar with:

cd grammars/lalrpop-rust
pnpm dlx tree-sitter-cli@0.25.10 test

After changing either grammar, commit grammars/lalrpop and grammars/lalrpop-rust first, then update both grammar revisions in editors/zed/extension.toml to that commit's full hash. Run zed: rebuild dev extension to compile and reload the changed grammars.

Zed compiles the adapter to WebAssembly when editors/zed is installed as a development extension. The language definition uses a patched vendored copy of tree-sitter-lalrpop for syntax-aware editor features. Rust action bodies are parsed as expressions by a small dialect of Zed's pinned tree-sitter-rust; the dialect adds LALRPOP's <> placeholder while retaining Zed's native Rust highlight captures.

Project status

This project is under active development. Please report issues in the GitHub issue tracker.

Credits

The server uses Tower LSP and is based on tower-lsp-boilerplate. The VS Code TextMate grammar originated in VSC_LalrpopHighlight.