Simon Willison’s Weblog

ast-grep (via) There are a lot of interesting things about this year-old project.

sg (an alias for ast-grep) is a CLI tool for running AST-based searches against code, built in Rust on top of the Tree-sitter parsing library. You can run commands like this:

sg -p ’await await_me_maybe($ARG)’ datasette --lang python

To search the datasette directory for code that matches the search pattern, in a syntax-aware way.

It works across 19 different languages, and can handle search-and-replace too, so it can work as a powerful syntax-aware refactoring tool.

My favourite detail is how it’s packaged. You can install the CLI utility using Homebrew, Cargo, npm or pip/pipx—each of which will give you a CLI tool you can start running. On top of that it provides API bindings for Rust, JavaScript and Python!