Emulator Idempotency: Auth

.changeset/lemon-candles-vanish.md

@@ -0,0 +1,8 @@
+---
+'@firebase/auth': patch
+'firebase': patch
+---
+
+Fixed: invoking `connectAuthEmulator` 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/auth/src/core/auth/emulator.test.ts

@@ -76,6 +76,41 @@ describe('core/auth/emulator', () => {
       );
     });
 
+    it('passes with same config if a network request has already been made', async () => {
+      expect(() => connectAuthEmulator(auth, 'http://127.0.0.1:2020')).to.not
+        .throw;
+      await user.delete();
+      expect(() => connectAuthEmulator(auth, 'http://127.0.0.1:2020')).to.not
+        .throw;
+    });
+
+    it('fails with alternate config if a network request has already been made', async () => {
+      expect(() => connectAuthEmulator(auth, 'http://127.0.0.1:2020')).to.not
+        .throw;
+      await user.delete();
+      expect(() => connectAuthEmulator(auth, 'http://127.0.0.1:2021')).to.throw(
+        FirebaseError,
+        'auth/emulator-config-failed'
+      );
+    });
+
+    it('subsequent calls update the endpoint appropriately', async () => {
+      connectAuthEmulator(auth, 'http://127.0.0.1:2021');
+      expect(auth.emulatorConfig).to.eql({
+        protocol: 'http',
+        host: '127.0.0.1',
+        port: 2021,
+        options: { disableWarnings: false }
+      });
+      connectAuthEmulator(auth, 'http://127.0.0.1:2020');
+      expect(auth.emulatorConfig).to.eql({
+        protocol: 'http',
+        host: '127.0.0.1',
+        port: 2020,
+        options: { disableWarnings: false }
+      });
+    });
+
     it('updates the endpoint appropriately', async () => {
       connectAuthEmulator(auth, 'http://127.0.0.1:2020');
       await user.delete();

packages/auth/src/core/auth/emulator.ts

@@ -18,6 +18,7 @@ import { Auth } from '../../model/public_types';
 import { AuthErrorCode } from '../errors';
 import { _assert } from '../util/assert';
 import { _castAuth } from './auth_impl';
+import { deepEqual } from '@firebase/util';
 
 /**
  * Changes the {@link Auth} instance to communicate with the Firebase Auth Emulator, instead of production
@@ -47,12 +48,6 @@ export function connectAuthEmulator(
   options?: { disableWarnings: boolean }
 ): void {
   const authInternal = _castAuth(auth);
-  _assert(
-    authInternal._canInitEmulator,
-    authInternal,
-    AuthErrorCode.EMULATOR_CONFIG_FAILED
-  );
-
   _assert(
     /^https?:\/\//.test(url),
     authInternal,
@@ -66,15 +61,42 @@ export function connectAuthEmulator(
   const portStr = port === null ? '' : `:${port}`;
 
   // Always replace path with "/" (even if input url had no path at all, or had a different one).
-  authInternal.config.emulator = { url: `${protocol}//${host}${portStr}/` };
-  authInternal.settings.appVerificationDisabledForTesting = true;
-  authInternal.emulatorConfig = Object.freeze({
+  const emulator = { url: `${protocol}//${host}${portStr}/` };
+  const emulatorConfig = Object.freeze({
     host,
     port,
     protocol: protocol.replace(':', ''),
     options: Object.freeze({ disableWarnings })
   });
 
+  // There are a few scenarios to guard against if the Auth instance has already started:
+  if (!authInternal._canInitEmulator) {
+    // Applications may not initialize the emulator for the first time if Auth has already started
+    // to make network requests.
+    _assert(
+      authInternal.config.emulator && authInternal.emulatorConfig,
+      authInternal,
+      AuthErrorCode.EMULATOR_CONFIG_FAILED
+    );
+
+    // Applications may not alter the configuration of the emulator (aka pass a different config)
+    // once Auth has started to make network requests.
+    _assert(
+      deepEqual(emulator, authInternal.config.emulator) &&
+        deepEqual(emulatorConfig, authInternal.emulatorConfig),
+      authInternal,
+      AuthErrorCode.EMULATOR_CONFIG_FAILED
+    );
+
+    // It's valid, however, to invoke connectAuthEmulator() after Auth has started making
+    // connections, so long as the config matches the existing config. This results in a no-op.
+    return;
+  }
+
+  authInternal.config.emulator = emulator;
+  authInternal.emulatorConfig = emulatorConfig;
+  authInternal.settings.appVerificationDisabledForTesting = true;
+
   if (!disableWarnings) {
     emitEmulatorWarning();
   }