ast-grep

AST-based code search locates specific language constructs by matching structural patterns rather than exact text. You write YAML rules defining kinds, patterns, and relational constraints, then run the ast-grep CLI to find matching code across your codebase.

Yes, complex structural code queries use relational rules like inside, has, precedes, and follows, combined with logical operators all, any, and not. This allows you to express deeply nested constraints and find patterns requiring structural context.

To find an async function with an await expression, write a YAML rule specifying kind: function_declaration and a has relation with pattern: await $EXPR. This matches the function declaration structurally and checks for the nested await pattern.

The best way to test structural code search rules is to validate them against sample code snippets first. After confirming the YAML rule logic matches expected constructs, run the ast-grep CLI to scan the real project and identify matches for refactoring or auditing.

No external dependencies are required to perform AST-based code searches. You only need to write YAML rules defining your structural patterns and use the ast-grep CLI tool to test and apply those rules against your codebase.

Structural AST search outperforms regex text matching for code auditing because it understands code syntax and language constructs. It accurately locates complex patterns regardless of formatting, whitespace, or variable names, preventing false positives common in plain text searches.