Function wrapInTimeout

front_end/testing/TraceLoader.ts:324–358

* Wraps an async Promise with a timeout. We use this to break down and * instrument `TraceLoader` to understand on CQ where timeouts occur. * * @param asyncPromise The Promise representing the async operation to be timed. * @param timeoutMs The timeout in milliseconds. * @param stepName An iden

(
    mochaContext: Mocha.Context|Mocha.Suite|null, callback: () => Promise<T>| T, timeoutMs: number,
    stepName: string)

 * @returns A promise that resolves with the operation's result, or rejects if it times out.
 */
async function wrapInTimeout<T>(
    mochaContext: Mocha.Context|Mocha.Suite|null, callback: () => Promise<T>| T, timeoutMs: number,
    stepName: string): Promise<T> {
  const timeout = Promise.withResolvers<void>();
  const timeoutId = setTimeout(() => {
    let testTitle = '(unknown test)';
    if (mochaContext) {
      try {
        if (isMochaContext(mochaContext)) {
          testTitle = mochaContext.currentTest?.fullTitle() ?? testTitle;
        } else {
          // For unknown reasons, we cannot trust the Mocha.Suite types in TS.
          // They may be out of sync with the karma-mocha plugin.
          // But, `suite.test.title` is present.
          testTitle = (mochaContext as unknown as {test: {title: string}}).test.title;
        }
      } catch (e) {
        console.error('Determining Mocha test context for trace timeout failed', e);
      }
    }
    console.error(`TraceLoader: [${stepName}]: took longer than ${timeoutMs}ms in test "${testTitle}"`);
    timeout.reject(new Error(`Timeout for TraceLoader: '${stepName}' after ${timeoutMs}ms.`));
  }, timeoutMs);

  // Race the original promise against the timeout promise
  try {
    const cbResult = await Promise.race([callback(), timeout.promise]);
    timeout.resolve();
    return cbResult as T;
  } finally {
    // Clear the timeout if the original promise resolves/rejects,
    // or if the timeout promise wins the race.
    clearTimeout(timeoutId);
  }
}

function isMochaContext(arg: unknown): arg is Mocha.Context {
  return typeof arg === 'object' && arg !== null && 'currentTest' in arg;