fix(app-check): guard missing initializeAppCheck options at runtime

Keep optional options matching firebase-js-sdk; reject undefined options
with the same error as the macOS path before native initialization.

Author: mikehardy

.github/scripts/compare-types/configs/app-check.ts

@@ -89,7 +89,7 @@ const config: PackageConfig = {
     {
       name: 'initializeAppCheck',
       reason:
-        'RN Firebase returns `Promise<AppCheck>` because App Check initialization crosses the native bridge, whereas the firebase-js-sdk returns `AppCheck` synchronously. The `options` argument is required on RN Firebase because native initialization always needs a configured provider; the firebase-js-sdk declaration marks it optional even though a provider is required in practice.',
+        'RN Firebase returns `Promise<AppCheck>` because App Check initialization crosses the native bridge, whereas the firebase-js-sdk returns `AppCheck` synchronously.',
     },
     {
       name: 'AppCheckOptions',

packages/app-check/__tests__/appcheck.test.ts

@@ -20,8 +20,8 @@ describe('appCheck()', function () {
       expect(initializeAppCheck).toBeDefined();
     });
 
-    it('`initializeAppCheck` rejects missing options', async function () {
-      await expect(initializeAppCheck(undefined, undefined as any)).rejects.toThrow(
+    it('`initializeAppCheck` rejects missing options at runtime', async function () {
+      await expect(initializeAppCheck(undefined, undefined)).rejects.toThrow(
         'Invalid configuration: no options defined.',
       );
     });

packages/app-check/lib/index.ts

@@ -255,8 +255,8 @@ function getModularAppCheck(app?: FirebaseApp): AppCheck {
 }
 
 export async function initializeAppCheck(
-  app: FirebaseApp | undefined,
-  options: AppCheckOptions,
+  app?: FirebaseApp,
+  options?: AppCheckOptions,
 ): Promise<AppCheck> {
   if (!isObject(options)) {
     throw new Error('Invalid configuration: no options defined.');

packages/app-check/type-test.ts

@@ -25,9 +25,6 @@ initializeAppCheck(getApp(), options).then((instance: AppCheck) => {
   console.log(instance.app.name);
 });
 
-// @ts-expect-error options is required for App Check initialization
-initializeAppCheck(getApp());
-
 getToken(appCheck).then((result: AppCheckTokenResult) => {
   console.log(result.token);
 });