ast-grep

To search code by structure, ast-grep translates natural language queries into AST rules that match code patterns rather than exact text. This allows you to find function calls, variable assignments, or specific syntax trees across large codebases.

Tree-sitter languages are fully supported for structural code search. The generated ast-grep rules apply to any language supported by Tree-sitter, enabling you to query language constructs and complex structural patterns across your codebase.

The best way to find complex nested patterns is using relational rules and metavariables. ast-grep generates rules with relational operators like `inside` and `has` to match flexible, deeply nested code structures across large codebases.

To generate and test an ast-grep rule, describe the code pattern you want to find. The workflow then creates a small test snippet, writes the rule, and validates it before you search the target codebase using the ast-grep CLI.

Yes, a test code snippet is required to create AST-based code search rules. The rule generation workflow needs a clear language target, a test snippet, and your natural language query to produce and validate executable ast-grep rules.

AST structural search is used over regex because it understands code syntax and language constructs. ast-grep rules match the actual structure of the code, ignoring formatting variations, comments, or whitespace that would break regular expression patterns.