firebase-js-sdk/packages/auth/test/integration/webdriver/static/middleware.js

/**
 * @license
 * Copyright 2022 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

export async function attachBlockingMiddleware() {
  auth.beforeAuthStateChanged(() => {
    throw new Error('block state change');
  });
}

export async function attachBlockingMiddlewareOnStart() {
  // Attaches the blocking middleware _immediately_ after auth is initialized,
  // allowing us to test redirect operations.
  const oldStartAuth = window.startAuth;

  window.startAuth = async () => {
    oldStartAuth();
    await attachBlockingMiddleware();
  };
}