Utility for knowing if an Identifier is a reference to a binding

[Rich-Harris]

When traversing an AST, is there an easy way to know if an Identifier node references a binding or not? In other words, this code...

const ast = parse(`foo; obj.bar`);

traverse(ast, {
  $: { scope: true },
  Identifier(path) {
    console.log(path.node.name);
  }
});

...will log this...

foo
obj
bar

...but only foo and obj are binding references. I have a package for this — is-reference — but it would be awesome if there was a way to do this within estree-toolkit. Thank you!

[sarsamurmu]

It's possible, currently there's no built-in utility function but you can make yourself one

const ast = parseModule(`
const foo = 0, obj = {};
const bar = 0;

foo;
obj.bar;
`);

/**
 * @param {NodePath} path 
 */
const isReference = (path) => {
  const binding = path.scope.getBinding(path.node.name);
  if (binding != null) {
    return path === binding.identifierPath || binding.references.includes(path)
  }
  return false
}

traverse(ast, {
  $: { scope: true },
  Identifier(path) {
    console.log(path.node.name, isReference(path))
  }
})

Output

foo true
obj true
bar true
foo true
obj true
bar false

[Rich-Harris]

Wonderful, thanks! That works for us — I'll leave this issue open in case you intend to expose a utility like that, but otherwise please consider this resolved

[sarsamurmu]

Just leaving this issue open, I will add this functionality to the library later