gecko-dev/testing/web-platform/tests/webrtc/tools/codemod-peerconnection-addcleanup

/* a codemod for ensuring RTCPeerConnection is cleaned up in tests.
 * For each `new RTCPeerConnection` add a
 * `test.add_cleanup(() => pc.close())`
 * Only applies in promise_tests if there is no add_cleanup in the
 * test function body.
 */
export default function transformer(file, api) {
  const j = api.jscodeshift;
  return j(file.source)
    // find each RTCPeerConnection constructor
    .find(j.NewExpression, {callee: {type: 'Identifier', name: 'RTCPeerConnection'}})

    // check it is inside a promise_test
    .filter(path => {
      // iterate parentPath until you find a CallExpression
      let nextPath = path.parentPath;
      while (nextPath && nextPath.value.type !== 'CallExpression') {
        nextPath = nextPath.parentPath;
      }
      return nextPath && nextPath.value.callee.name === 'promise_test';
    })
    // check there is no add_cleanup in the function body
    .filter(path => {
      let nextPath = path.parentPath;
      while (nextPath && nextPath.value.type !== 'CallExpression') {
        nextPath = nextPath.parentPath;
      }
      const body = nextPath.value.arguments[0].body;
      return j(body).find(j.Identifier, {name: 'add_cleanup'}).length === 0;
    })
    .forEach(path => {
      // iterate parentPath until you find a CallExpression
      let nextPath = path.parentPath;
      while (nextPath && nextPath.value.type !== 'CallExpression') {
        nextPath = nextPath.parentPath;
      }
      const declaration = path.parentPath.parentPath.parentPath;
      const pc = path.parentPath.value.id;

      declaration.insertAfter(
        j.expressionStatement(
          j.callExpression(
            j.memberExpression(
              nextPath.node.arguments[0].params[0],
              j.identifier('add_cleanup')
            ),
            [j.arrowFunctionExpression([],
              j.callExpression(
                j.memberExpression(pc, j.identifier('close'), false),
                []
              )
            )]
          )
        )
      );
    })
    .toSource();
};