ast-grep: Structural Code Search and Editing
Always invoke the ast-grep skill for structural code search and refactoring - do not execute bash commands directly.
Default Strategy
Invoke analyzing-code-structure skill for structural code search and refactoring. Use when:
- Text-based Edit tool fails with "old_string not unique"
- Need formatting-independent pattern matching
- Performing structural changes across code
Common workflow: Invoke extracting-code-structure skill first, then analyzing-code-structure skill for structural modifications.
Use ast-grep to solve the "old_string not unique" problem by matching code structure instead of exact text. This enables refactoring across formatting variations and structural patterns.
When to Use analyzing-code-structure vs Text Tools
Use analyzing-code-structure when:
- Structural code changes - Refactoring function signatures, method calls, class structures
- Formatting-independent matching - Need to find code regardless of whitespace/line breaks
- Pattern variations - Matching similar structures with different variable names/arguments
- "old_string not unique" problem - Edit tool fails because text appears in multiple contexts
- Complex queries - Finding nested structures, specific AST patterns
Use text tools (Edit/Grep) when:
- Simple, unique string replacement - The exact text appears once or in consistent format
- Non-code files - Markdown, configs, data files
- Comment/documentation edits - Content that isn't code structure
- Very small changes - Single line, obvious context, no ambiguity
Key Decision Rule
If editing code structure and there's any ambiguity in text matching → use analyzing-code-structure.
ast-grep's primary value: Solves the "old_string not unique" problem by matching structure instead of exact text.
Detailed Reference
For comprehensive patterns, syntax, metavariables, common use cases, language-specific tips, and best practices, load analyzing-code-structure guide when needing:
- Complex pattern matching with metavariables
- Language-specific syntax variations
- Advanced refactoring workflows
- Integration with other tools
- Common pitfalls and solutions
The reference includes:
- Pattern syntax and metavariables (
$VAR,$$$ARGS,$$STMT) - Recommended workflow (search, verify, apply, validate)
- Common use cases with examples (function calls, imports, method renames)
- Language-specific tips (JavaScript/TypeScript, Python, Go, Rust)
- Best practices and pitfalls to avoid
- Integration strategies with Edit tool
Skill Combinations
For Discovery Phase
- extracting-code-structure → analyzing-code-structure: Get code outline first, then perform structural refactoring
- searching-text → analyzing-code-structure: Search text patterns to locate areas needing structural changes
- finding-files → analyzing-code-structure: Find files of specific type, then apply structural modifications
For Analysis Phase
- analyzing-code-structure → viewing-files: Preview changes with syntax highlighting before committing
- analyzing-code-structure → searching-text: Verify no unintended occurrences remain
- analyzing-code-structure → extracting-code-structure: Validate structural changes against code outline
For Refactoring Phase
- analyzing-code-structure → analyzing-code: Measure changes impact on code statistics
- analyzing-code-structure → replacing-text: Follow structural changes with text-based replacements if needed
- analyzing-code-structure → querying-json/querying-yaml: Update configuration files related to code changes