Zed Extension

The Beacon Zed extension (pkg/zed/) integrates the Beacon language server with Zed editor. It activates automatically for Python files and provides Hindley-Milner type checking alongside standard LSP features.

Feature Highlights

• On-type diagnostics for syntax and type errors
• Hover tooltips with type information
• Go to definition & find references
• Document and workspace symbols
• Semantic tokens for enhanced highlighting
• Identifier completions and inlay hints
• Code actions for quick fixes and refactoring

These capabilities mirror the features exposed by the Rust server in crates/server.

Repository Layout

pkg/zed/
├── src/
│   └── lib.rs       # Extension implementation
├── Cargo.toml       # Rust project manifest
├── extension.toml   # Zed extension metadata
└── README.md        # Installation instructions

The extension is compiled to WebAssembly (wasm32-wasip1) and communicates with the beacon-lsp binary via the Language Server Protocol.

Prerequisites

• Rust toolchain (stable) with cargo available in PATH
• wasm32-wasip1 target for Rust (install with rustup target add wasm32-wasip1)
• beacon-lsp binary installed and available in PATH
• Zed editor installed

Installing beacon-lsp

The extension requires beacon-lsp to be available in your system PATH:

# From the repository root
cargo install --path crates/server

This installs the beacon-lsp binary to ~/.cargo/bin. Ensure ~/.cargo/bin is in your PATH.

Verify installation:

which beacon-lsp
# Should output: /Users/<username>/.cargo/bin/beacon-lsp

Building The Extension

The extension must be compiled to WebAssembly:

cd pkg/zed
cargo build --target wasm32-wasip1 --release

The compiled extension will be at:

target/wasm32-wasip1/release/beacon_zed.wasm

Installing The Extension

Development Installation

For local development and testing:

1. Build the extension (see above)

2. Create a symlink to the extension directory in Zed's extensions folder:

   # macOS
   mkdir -p ~/.config/zed/extensions
   ln -s /path/to/beacon/pkg/zed ~/.config/zed/extensions/beacon
   

3. Restart Zed or reload the window

4. Open a Python file to activate the extension

Distribution Installation

To distribute the extension, package it following Zed's extension installation guide.

The extension expects beacon-lsp to be available in the user's PATH. Users should install it via:

cargo install beacon-lsp

Extension Implementation

The extension implements the zed::Extension trait with the following key components:

Language Server Command

Returns the command to launch beacon-lsp:

#![allow(unused)]
fn main() {
fn language_server_command(
    &mut self, _: &zed::LanguageServerId, worktree: &zed::Worktree) -> zed::Result<zed::Command> {
    let command = worktree
        .which("beacon-lsp")
        .ok_or_else(|| "beacon-lsp not found in PATH")?;

    Ok(zed::Command {
        command,
        args: vec![],
        env: vec![("RUST_LOG".to_string(), "info".to_string())],
    })
}
}

Environment Variables

The extension sets RUST_LOG=info to configure logging. Logs are written to stderr and can be viewed in Zed's log panel.

Arguments

beacon-lsp doesn't require command-line arguments as it communicates via stdin/stdout.

Configuration

See Configurationfor details.

Development Workflow

Making Changes

1. Edit the extension source in pkg/zed/src/lib.rs

2. Rebuild the extension:

   cargo build --target wasm32-wasip1 --release
   

3. Restart Zed to load the updated extension

Debugging

Enable detailed logging:

RUST_LOG=beacon_lsp=debug zed

Or set the environment variable in your shell before launching Zed. Logs appear in:

• macOS: ~/Library/Logs/Zed/Zed.log
• Linux: ~/.local/share/zed/logs/Zed.log

Testing Changes

1. Build the language server with your changes:

   cargo build -p beacon-lsp
   cargo install --path crates/server
   

2. Rebuild the extension if needed

3. Open a Python project in Zed

4. Test LSP features:

   • Hover over variables to see type information
   • Use Cmd+Click (macOS) or Ctrl+Click (Linux) for go-to-definition
   • Check the Problems panel for diagnostics
   • Trigger completions with Ctrl+Space

Comparison with VS Code Extension

Both extensions use the same beacon-lsp server, so feature parity is guaranteed.

Resources

• Zed Extension Development
• Zed Language Extensions
• Zed Extension API
• Language Server Protocol
• Beacon Configuration