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