travbid / mypyls

Mypy language server: runs mypy on Python code to provide type checking, go to definition, and hover.

Mypy Language Server

Runs mypy on Python code to provide type checking, go to definition, and hover.

Installation

Follow the installation instructions in Mypy extension for VS Code. Using the VS Code extension itself is not required -- the language server may be used with any editor that supports the Language Server Protocol.

Motivation

Why another language server for Python? There are already at least Palantir's python-language-server (uses jedi), pyright (uses analysis engine written in TypeScript), Microsoft's python-language-server (uses analysis engine written in C#), and PyCharm (does not provide language server conforming to Language Server Protocol; uses analysis engine written in Java).

Mypy has a robust type checking engine that is focused on correctness. Other IDE tools use custom analysis engines and the provided language features do not always match mypy's analysis. In a future where type-annotated Python is more common, it would be useful to have mypy's robust analysis provide the basis for IDE features as 'one source truth'. This language server is a proof of concept for that, although it is currently quite hacky and uses private mypy APIs. The mypy team might be working on an official integration in the future.

License

This project is made available under the MIT License. It is based on Palantir's python-language-server and uses mypy.