ast-grep

ast-grep Code Search

Overview

This skill helps translate natural language queries into ast-grep rules for structural code search. ast-grep uses Abstract Syntax Tree (AST) patterns to match code based on its structure rather than just text, enabling powerful and precise code search across large codebases.

When to Use This Skill

Use this skill when users:

• Need to search for code patterns using structural matching (e.g., "find all async functions that don't have error handling")
• Want to locate specific language constructs (e.g., "find all function calls with specific parameters")
• Request searches that require understanding code structure rather than just text
• Ask to search for code with particular AST characteristics
• Need to perform complex code queries that traditional text search cannot handle

General Workflow

Follow this process to help users write effective ast-grep rules:

Step 1: Understand the Query

Clearly understand what the user wants to find. Ask clarifying questions if needed:

• What specific code pattern or structure are they looking for?
• Which programming language?
• Are there specific edge cases or variations to consider?
• What should be included or excluded from matches?

Step 2: Create Example Code

Write a simple code snippet that represents what the user wants to match. Save this to a temporary file for testing.

Example: If searching for "async functions that use await", create a test file:

// test_example.js
async function example() {
  const result = await fetchData();
  return result;
}

Step 3: Write the ast-grep Rule

Translate the pattern into an ast-grep rule. Start simple and add complexity as needed.

Key principles:

• Always use stopBy: end for relational rules (inside, has) to ensure search goes to the end of the direction
• Use pattern for simple structures
• Use kind with has/inside for complex structures
• Break complex queries into smaller sub-rules using all, any, or not