Function batchChangeDetection

src/cdk/testing/change-detection.ts:69–111

* Batches together triggering of change detection over the duration of the given function. * @param fn The function to call with batched change detection. * @param triggerBeforeAndAfter Optionally trigger change detection once before and after the batch * operation. If false, change detection w

(fn: () => Promise<T>, triggerBeforeAndAfter: boolean)

 * @return The result of the given function.
 */
async function batchChangeDetection<T>(fn: () => Promise<T>, triggerBeforeAndAfter: boolean) {
  // If change detection batching is already in progress, just run the function.
  if (autoChangeDetectionSubject.getValue().isDisabled) {
    return await fn();
  }

  // If nothing is handling change detection batching, install the default handler.
  if (!autoChangeDetectionSubscription) {
    handleAutoChangeDetectionStatus(defaultAutoChangeDetectionHandler);
  }

  if (triggerBeforeAndAfter) {
    await new Promise(resolve =>
      autoChangeDetectionSubject.next({
        isDisabled: true,
        onDetectChangesNow: resolve as () => void,
      }),
    );
    // The function passed in may throw (e.g. if the user wants to make an expectation of an error
    // being thrown. If this happens, we need to make sure we still re-enable change detection, so
    // we wrap it in a `finally` block.
    try {
      return await fn();
    } finally {
      await new Promise(resolve =>
        autoChangeDetectionSubject.next({
          isDisabled: false,
          onDetectChangesNow: resolve as () => void,
        }),
      );
    }
  } else {
    autoChangeDetectionSubject.next({isDisabled: true});
    // The function passed in may throw (e.g. if the user wants to make an expectation of an error
    // being thrown. If this happens, we need to make sure we still re-enable change detection, so
    // we wrap it in a `finally` block.
    try {
      return await fn();
    } finally {
      autoChangeDetectionSubject.next({isDisabled: false});
    }
  }
}

/**
 * Disables the harness system's auto change detection for the duration of the given function.