fix: add firebase-messaging gradle dependency to app module

The native module declares firebase-messaging as an `implementation`
dependency, which is private to the library module. Since the generated
FirebaseMessagingService lives in the app module, it needs
firebase-messaging on its own compile classpath. Conditionally adds the
dependency to app/build.gradle if not already present.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Rosie-Kennelly-1

__tests__/withAndroidPushNotifications.test.ts

@@ -40,12 +40,26 @@ function createMockConfig(packageName?: string) {
 describe('withAndroidPushNotifications', () => {
   let mkdirSyncSpy: jest.SpyInstance;
   let writeFileSyncSpy: jest.SpyInstance;
+  let readFileSyncSpy: jest.SpyInstance;
+
+  const fakeBuildGradle = `
+android {
+    compileSdkVersion 34
+}
+
+dependencies {
+    implementation("com.facebook.react:react-native:+")
+}
+`;
 
   beforeEach(() => {
     mkdirSyncSpy = jest.spyOn(fs, 'mkdirSync').mockReturnValue(undefined);
     writeFileSyncSpy = jest
       .spyOn(fs, 'writeFileSync')
       .mockReturnValue(undefined);
+    readFileSyncSpy = jest
+      .spyOn(fs, 'readFileSync')
+      .mockReturnValue(fakeBuildGradle);
   });
 
   afterEach(() => {
@@ -139,6 +153,32 @@ describe('withAndroidPushNotifications', () => {
     });
   });
 
+  describe('Gradle dependency', () => {
+    test('adds firebase-messaging when not present', () => {
+      const config = createMockConfig('com.example.myapp');
+      withAndroidPushNotifications(config as any, {} as any);
+
+      const gradleWriteCall = writeFileSyncSpy.mock.calls.find(
+        (call: any[]) => (call[0] as string).includes('build.gradle')
+      );
+      expect(gradleWriteCall).toBeDefined();
+      expect(gradleWriteCall[1]).toContain('firebase-messaging');
+    });
+
+    test('skips adding firebase-messaging when already present', () => {
+      readFileSyncSpy.mockReturnValue(
+        'dependencies {\n    implementation("com.google.firebase:firebase-messaging:23.0.0")\n}'
+      );
+      const config = createMockConfig('com.example.myapp');
+      withAndroidPushNotifications(config as any, {} as any);
+
+      const gradleWriteCall = writeFileSyncSpy.mock.calls.find(
+        (call: any[]) => (call[0] as string).includes('build.gradle')
+      );
+      expect(gradleWriteCall).toBeUndefined();
+    });
+  });
+
   describe('AndroidManifest service registration', () => {
     test('adds service entry with correct attributes', () => {
       const config = createMockConfig('com.example.myapp');

src/expo-plugins/withAndroidPushNotifications.ts

@@ -74,6 +74,25 @@ const writeFirebaseService: ConfigPlugin<IntercomPluginProps> = (_config) =>
         'utf-8'
       );
 
+      // The native module declares firebase-messaging as an `implementation`
+      // dependency, which keeps it private to the library. Since our generated
+      // service lives in the app module, we need firebase-messaging on the
+      // app's compile classpath too.
+      const buildGradlePath = path.join(
+        projectRoot,
+        'android',
+        'app',
+        'build.gradle'
+      );
+      const buildGradle = fs.readFileSync(buildGradlePath, 'utf-8');
+      if (!buildGradle.includes('firebase-messaging')) {
+        const updatedBuildGradle = buildGradle.replace(
+          /dependencies\s*\{/,
+          `dependencies {\n    implementation("com.google.firebase:firebase-messaging:24.1.2")`
+        );
+        fs.writeFileSync(buildGradlePath, updatedBuildGradle, 'utf-8');
+      }
+
       return config;
     },
   ]);