rust-analyzer-mcp: Instructions file for Claude Code

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

rust-analyzer-mcp is a Model Context Protocol (MCP) server that provides integration with rust-analyzer LSP, allowing AI assistants to analyze Rust code through standardized tools. The server acts as a bridge between MCP clients and rust-analyzer, translating MCP tool calls into LSP requests.

Architecture

The codebase follows a modular architecture:

• Main MCP Server (src/main.rs): Handles MCP protocol, manages rust-analyzer subprocess, and routes tool calls to LSP methods
• Test Support Library (test-support/): Provides MCPTestClient for integration testing with proper process lifecycle management
• Test Structure:
  • tests/integration/: Core MCP server integration tests
  • tests/stress/: Concurrency and performance stress tests
  • tests/unit/: Protocol and component unit tests
  • tests/property/: Property-based fuzzing tests

Key architectural decisions:

• Uses Tokio async runtime for concurrent request handling
• Maintains persistent rust-analyzer subprocess for performance
• Implements proper LSP initialization sequence with workspace support
• Handles CI environment detection for test reliability

Development Commands

Building and Running

# Development build and run
cargo build
cargo run -- /path/to/workspace

# Release build (optimized with LTO)
cargo build --release

# Run with debug logging
RUST_LOG=debug cargo run -- /path/to/workspace

Testing

# Run all tests
cargo test

# Run specific test
cargo test test_concurrent_tool_calls

# Run tests in release mode (for stress tests)
cargo test --release

# Run integration tests only
cargo test --test integration_tests

# Run with verbose output to debug failures
cargo test -- --nocapture

# Run tests with specific timeout debugging
RUST_BACKTRACE=1 cargo test --test integration_tests test_all_lsp_tools

Linting and Formatting