Emulator Idempotency: Database

.changeset/forty-bags-arrive.md

@@ -0,0 +1,8 @@
+---
+'@firebase/database-compat': patch
+'@firebase/database': patch
+'firebase': patch
+---
+
+Fixed: invoking `connectDatabaseEmulator` multiple times with the same parameters will no longer
+cause an error. Fixes [GitHub Issue #6824](https://github.com/firebase/firebase-js-sdk/issues/6824).

packages/database-compat/test/database.test.ts

@@ -301,7 +301,9 @@ describe('Database Tests', () => {
 
     expect(() => {
       db.useEmulator('localhost', 1234);
-    }).to.throw(/Cannot call useEmulator/);
+    }).to.throw(
+      'FIREBASE FATAL ERROR: connectDatabaseEmulator() cannot initialize or alter the emulator configuration after the database instance has started.'
+    );
   });
 
   it('refFromURL returns an emulated ref with useEmulator', () => {

packages/database/src/api/Database.ts

@@ -27,6 +27,7 @@ import { Provider } from '@firebase/component';
 import {
   getModularInstance,
   createMockUserToken,
+  deepEqual,
   EmulatorMockTokenOptions,
   getDefaultEmulatorHostnameAndPort
 } from '@firebase/util';
@@ -38,7 +39,7 @@ import {
   FirebaseAuthTokenProvider
 } from '../core/AuthTokenProvider';
 import { Repo, repoInterrupt, repoResume, repoStart } from '../core/Repo';
-import { RepoInfo } from '../core/RepoInfo';
+import { RepoInfo, RepoInfoEmulatorOptions } from '../core/RepoInfo';
 import { parseRepoInfo } from '../core/util/libs/parser';
 import { newEmptyPath, pathIsEmpty } from '../core/util/Path';
 import {
@@ -84,19 +85,20 @@ let useRestClient = false;
  */
 function repoManagerApplyEmulatorSettings(
   repo: Repo,
-  host: string,
-  port: number,
+  hostAndPort: string,
+  emulatorOptions: RepoInfoEmulatorOptions,
   tokenProvider?: AuthTokenProvider
 ): void {
   repo.repoInfo_ = new RepoInfo(
-    `${host}:${port}`,
+    hostAndPort,
     /* secure= */ false,
     repo.repoInfo_.namespace,
     repo.repoInfo_.webSocketOnly,
     repo.repoInfo_.nodeAdmin,
     repo.repoInfo_.persistenceKey,
     repo.repoInfo_.includeNamespaceInQueryParams,
-    /*isUsingEmulator=*/ true
+    /*isUsingEmulator=*/ true,
+    emulatorOptions
   );
 
   if (tokenProvider) {
@@ -350,13 +352,22 @@ export function connectDatabaseEmulator(
 ): void {
   db = getModularInstance(db);
   db._checkNotDeleted('useEmulator');
+  const hostAndPort = `${host}:${port}`;
+  const repo = db._repoInternal;
   if (db._instanceStarted) {
+    // If the instance has already been started, then silenty fail if this function is called again
+    // with the same parameters. If the parameters differ then assert.
+    if (
+      hostAndPort === db._repoInternal.repoInfo_.host &&
+      deepEqual(options, repo.repoInfo_.emulatorOptions)
+    ) {
+      return;
+    }
     fatal(
-      'Cannot call useEmulator() after instance has already been initialized.'
+      'connectDatabaseEmulator() cannot initialize or alter the emulator configuration after the database instance has started.'
     );
   }
 
-  const repo = db._repoInternal;
   let tokenProvider: EmulatorTokenProvider | undefined = undefined;
   if (repo.repoInfo_.nodeAdmin) {
     if (options.mockUserToken) {
@@ -374,7 +385,7 @@ export function connectDatabaseEmulator(
   }
 
   // Modify the repo to apply emulator settings
-  repoManagerApplyEmulatorSettings(repo, host, port, tokenProvider);
+  repoManagerApplyEmulatorSettings(repo, hostAndPort, options, tokenProvider);
 }
 
 /**

packages/database/src/core/RepoInfo.ts

@@ -15,13 +15,17 @@
  * limitations under the License.
  */
 
-import { assert } from '@firebase/util';
+import { assert, EmulatorMockTokenOptions } from '@firebase/util';
 
 import { LONG_POLLING, WEBSOCKET } from '../realtime/Constants';
 
 import { PersistentStorage } from './storage/storage';
 import { each } from './util/util';
 
+export interface RepoInfoEmulatorOptions {
+  mockUserToken?: string | EmulatorMockTokenOptions;
+}
+
 /**
  * A class that holds metadata about a Repo object
  */
@@ -46,7 +50,8 @@ export class RepoInfo {
     public readonly nodeAdmin: boolean = false,
     public readonly persistenceKey: string = '',
     public readonly includeNamespaceInQueryParams: boolean = false,
-    public readonly isUsingEmulator: boolean = false
+    public readonly isUsingEmulator: boolean = false,
+    public readonly emulatorOptions: RepoInfoEmulatorOptions | null = null
   ) {
     this._host = host.toLowerCase();
     this._domain = this._host.substr(this._host.indexOf('.') + 1);

packages/database/test/exp/integration.test.ts

@@ -35,6 +35,7 @@ import {
   orderByKey
 } from '../../src/api/Reference_impl';
 import {
+  connectDatabaseEmulator,
   getDatabase,
   goOffline,
   goOnline,
@@ -46,8 +47,10 @@ import { EventAccumulatorFactory } from '../helpers/EventAccumulator';
 import {
   DATABASE_ADDRESS,
   DATABASE_URL,
+  EMULATOR_PORT,
   getFreshRepo,
   getRWRefs,
+  USE_EMULATOR,
   waitFor,
   waitUntil,
   writeAndValidate
@@ -138,6 +141,37 @@ describe('Database@exp Tests', () => {
     unsubscribe();
   });
 
+  if (USE_EMULATOR) {
+    it('can connect to emulator', async () => {
+      const db = getDatabase(defaultApp);
+      connectDatabaseEmulator(db, 'localhost', parseInt(EMULATOR_PORT, 10));
+      await get(refFromURL(db, `${DATABASE_ADDRESS}/foo/bar`));
+    });
+    it('can change emulator config before network operations', async () => {
+      const db = getDatabase(defaultApp);
+      const port = parseInt(EMULATOR_PORT, 10);
+      connectDatabaseEmulator(db, 'localhost', port + 1);
+      connectDatabaseEmulator(db, 'localhost', port);
+      await get(refFromURL(db, `${DATABASE_ADDRESS}/foo/bar`));
+    });
+    it('can connect to emulator after network operations with same parameters', async () => {
+      const db = getDatabase(defaultApp);
+      const port = parseInt(EMULATOR_PORT, 10);
+      connectDatabaseEmulator(db, 'localhost', port);
+      await get(refFromURL(db, `${DATABASE_ADDRESS}/foo/bar`));
+      connectDatabaseEmulator(db, 'localhost', port);
+    });
+    it('cannot connect to emulator after network operations with different parameters', async () => {
+      const db = getDatabase(defaultApp);
+      const port = parseInt(EMULATOR_PORT, 10);
+      connectDatabaseEmulator(db, 'localhost', port);
+      await get(refFromURL(db, `${DATABASE_ADDRESS}/foo/bar`));
+      expect(() => {
+        connectDatabaseEmulator(db, 'localhost', 9001);
+      }).to.throw();
+    });
+  }
+
   it('can properly handle unknown deep merges', async () => {
     // Note: This test requires `testIndex` to be added as an index.
     // Please run `yarn test:setup` to ensure that this gets added.

packages/database/test/helpers/util.ts

@@ -33,9 +33,9 @@ import { EventAccumulator } from './EventAccumulator';
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 export const TEST_PROJECT = require('../../../../config/project.json');
-const EMULATOR_PORT = process.env.RTDB_EMULATOR_PORT;
+export const EMULATOR_PORT = process.env.RTDB_EMULATOR_PORT;
 const EMULATOR_NAMESPACE = process.env.RTDB_EMULATOR_NAMESPACE;
-const USE_EMULATOR = !!EMULATOR_PORT;
+export const USE_EMULATOR = !!EMULATOR_PORT;
 
 let freshRepoId = 0;
 const activeFreshApps: FirebaseApp[] = [];