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ast-grep

@natsukium/dotfiles
90
0

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.

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SKILL.md

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

I need to find all React components using useState I'll find useState usage in React components: `ast-grep --pattern 'const [$STATE, $SETTER] = useState($$$)'` Replace && chains with optional chaining for null checks I'll modernize null checks to optional chaining: `ast-grep --pattern '$OBJ && $OBJ.$PROP' --rewrite '$OBJ?.$PROP' --interactive` Find async functions that don't have error handling I'll search for async functions without try-catch: `ast-grep --pattern 'async function $NAME($$$PARAMS) { $$$BODY }' | grep -v try` Find all TypeScript interfaces I'll search for TypeScript interfaces: `ast-grep --pattern 'interface $NAME { $$$BODY }' --lang ts` I want to find potential null pointer exceptions I'll search for property access without null checks: `ast-grep --pattern '$VAR.$PROP' --filter 'not match { $VAR?.$PROP }'`