LLM_DEFINITION_TOOL.md

LLM Definition Tool for ElixirLS

This feature adds a VS Code language model tool that allows LLMs to look up Elixir symbol definitions and retrieve their source code.

Implementation Overview

VS Code Extension (TypeScript)

• package.json: Registers the elixir-definition language model tool
• src/definition-tool.ts: Implements the DefinitionTool class that handles tool invocations
• src/extension.ts: Registers the tool when language clients are ready

ElixirLS Language Server (Elixir)

• execute_command.ex: Added llmDefinition to the command handlers
• llm_definition.ex: Implements the command handler that:
  • Parses symbol strings (e.g., "MyModule", "MyModule.function", "MyModule.function/2")
  • Locates definitions using the existing Location.find_mod_fun_source/3
  • Uses the Location's range (start_line, start_column, end_line, end_column) to extract the exact definition text
  • Extracts additional context like @doc and @spec attributes before the definition
  • Returns formatted source with file location information

Usage

The tool can be invoked by LLMs with symbol names in various formats:

• Module: "MyModule" or "MyModule.SubModule"
• Function: "MyModule.my_function" or "MyModule.my_function/2"
• Erlang module: ":erlang" or ":ets"

Example Response

# Definition found in /path/to/file.ex:42

@doc """
Documentation for the function
"""
@spec my_function(term()) :: {:ok, term()} | {:error, String.t()}
def my_function(arg) do
  # Implementation
end

Testing

To test the implementation:

1. Build the extension: npm run compile && npm run vscode:prepublish
2. Launch VS Code with the extension
3. Open an Elixir project
4. Use GitHub Copilot or another LLM that supports language tools
5. Reference the tool with @elixir-definition and provide a symbol name

Future Enhancements

• Support for more symbol types (macros, structs, protocols)
• Include @doc and @spec in all cases
• Better handling of multi-clause functions
• Support for finding references/usages
• Caching for improved performance