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name: ast-grep description: AST-based code search and transformation tool using tree-sitter. Use for structural pattern matching, refactoring deprecated APIs, detecting anti-patterns, migrating code between library versions, and enforcing coding standards.

ast-grep - AST-based Code Search and Transformation

ast-grep is an AST-based tool for searching, linting, and refactoring code across multiple languages. It uses tree-sitter to parse code into Abstract Syntax Trees, enabling precise structural pattern matching.

Key Pattern Syntax

• $META - Matches a single AST node (e.g., $VAR, $FUNC, $ARG)
• $$$ - Matches zero or more AST nodes (useful for function arguments, statements)
• $_ - Non-capturing metavariable (matches but doesn't capture)
• Patterns must be syntactically valid code in the target language

Triggers

AST pattern, structural search, code refactoring, find anti-patterns, migrate code, console.log, deprecated API, function definition, class search, method signature, unused variables, security vulnerabilities, code transformation, pattern matching

When to Use

• Finding specific code patterns across large codebases
• Refactoring code (replacing deprecated APIs, updating syntax)
• Detecting anti-patterns or potential bugs
• Migrating between library versions
• Enforcing coding standards
• Interactive code rewriting

Examples