ast-grep

Use ast-grep (CLI binary ast-grep or sg) for structural, syntax-tree aware code search.

Decision Boundary: ast-grep vs ripgrep

• Use ripgrep (rg) when:

  • Searching for exact literal strings, comments, import paths, or single-line identifiers.
  • Searching non-AST/plain text files (markdown, JSON, YAML, config files).

• Use ast-grep when:

  • Matching multiline code blocks, call signatures, or nested control structures.
  • Searching for code pattern equivalence regardless of formatting, spacing, or line breaks.
  • Filtering out false positives in comments or string literals.
  • Searching for functions called with specific argument patterns (e.g. callback functions, specific parameter types).

CLI Command Usage

Execute searches:

ast-grep run --pattern '<PATTERN>' --lang <LANG> <DIR>

Or short alias:

sg run -p '<PATTERN>' -l <LANG> <DIR>

Common Language Identifiers (-l / --lang)

ts, tsx, js, jsx, python, go, rust, cpp, c, html, css.

Pattern Syntax Cheat Sheet

Syntax	Description	Example
$VAR	Single AST node variable	foo($A, $B)
$$$ARGS	Zero or more AST nodes (spread metavariable)	console.log($$$ARGS)
___	Wildcard single node (anonymous)	if (___) { $$$ }

Syntax Examples

1. Find all function calls with callback as last argument:

   ast-grep run -p '$FUNC($$$ARGS, ($$$PARAMS) => { $$$BODY })' -l ts .
   

2. Find specific JSX/TSX element usage:

   ast-grep run -p '<Button onClick={$HANDLER}>$$$CHILDREN</Button>' -l tsx .
   

3. Find error logging calls:

   ast-grep run -p 'logger.error($$$ARGS)' -l ts src/
   

4. Find async functions without try-catch:

   ast-grep run -p 'async function $NAME($$$ARGS) { $$$BODY }' -l ts src/