ast-grep

Fast and polyglot tool for code structural search, lint, rewriting at large scale.

• Official Website

Examples

# Pattern: `println!($$$)`
sg -p "println!(\$\$\$)"

Pattern

sg uses pattern code to construct Abstract Syntax Tree and match that against target code:

// `a+1` will match the following (expressions in) code:
const b = a + 1;
funcCall(a + 1);
deeplyNested({
  target: a + 1,
});

We can match dynamic content with meta variables:

• Meta variable: $ matches one single AST node, can be named.
• Multi-meta variable: $$$ matches zero or more AST node, can be named.

Named variable can be captured like capture group in regular expressions.

// `$A == $A` will match the following code:
a == a;
1 + 1 == 1 + 1;

// `function $FUNC($$$ARGS) { $$$ }` will match the following code:
function foo(bar) {
  return bar;
}
function noop() {}
function add(a, b, c) {
  return a + b + c;
}