ast-grep

ast-grep is a command-line tool that helps developers find and modify code patterns using abstract syntax trees instead of regular expressions. It works by parsing code into ASTs and matching patterns based on the actual syntax structure of programming languages. This approach allows for more precise code searching and transformation than traditional text-based tools like grep or sed.

The tool supports over 20 programming languages out of the box, including JavaScript, TypeScript, Python, Rust, and Java, with the ability to load custom tree-sitter parsers for additional languages. It offers multiple usage modes from simple command-line operations to a full programmatic Node.js API. The Rust-based parallel processing engine ensures fast performance even when scanning thousands of files, and it includes practical features like interactive codemod previews and a language server.

ast-grep benefits developers working on large codebases who need to perform systematic code changes, create custom linting rules, or maintain consistent code patterns across multiple projects. Real-world use cases include refactoring code to new patterns, eliminating anti-patterns, automating code style enforcement, and preparing code for major library migrations.