fix: making auth and firestore observable compatible

packages/auth/e2e/auth.e2e.js

@@ -187,6 +187,42 @@ describe('auth()', () => {
       unsubscribe();
     });
 
+    it('accept observer instead callback as well', async () => {
+      await firebase.auth().signInAnonymously();
+
+      await Utils.sleep(50);
+
+      // Test
+      const observer = {
+        next(user) {
+          // Test this access
+          this.onNext();
+          this.user = user;
+        },
+      };
+
+      let unsubscribe;
+      await new Promise(resolve => {
+        observer.onNext = resolve;
+        unsubscribe = firebase.auth().onAuthStateChanged(observer);
+      });
+      should.exist(observer.user);
+
+      // Sign out
+
+      await firebase.auth().signOut();
+
+      // Assertions
+
+      await Utils.sleep(50);
+
+      should.not.exist(observer.user);
+
+      // Tear down
+
+      unsubscribe();
+    });
+
     it('stops listening when unsubscribed', async () => {
       await firebase.auth().signInAnonymously();
 

packages/auth/lib/index.d.ts

@@ -1254,7 +1254,7 @@ export namespace FirebaseAuthTypes {
      *
      * @param listener A listener function which triggers when auth state changed (for example signing out).
      */
-    onAuthStateChanged(listener: AuthListenerCallback): () => void;
+    onAuthStateChanged(listener: CallbackOrObserver<AuthListenerCallback>): () => void;
 
     /**
      * Listen for changes in ID token.
@@ -1276,7 +1276,7 @@ export namespace FirebaseAuthTypes {
      *
      * @param listener A listener function which triggers when the users ID token changes.
      */
-    onIdTokenChanged(listener: AuthListenerCallback): () => void;
+    onIdTokenChanged(listener: CallbackOrObserver<AuthListenerCallback>): () => void;
 
     /**
      * Adds a listener to observe changes to the User object. This is a superset of everything from
@@ -1302,7 +1302,7 @@ export namespace FirebaseAuthTypes {
      * @react-native-firebase
      * @param listener A listener function which triggers when the users data changes.
      */
-    onUserChanged(listener: AuthListenerCallback): () => void;
+    onUserChanged(listener: CallbackOrObserver<AuthListenerCallback>): () => void;
 
     /**
      * Signs the user out.
@@ -1634,6 +1634,8 @@ export namespace FirebaseAuthTypes {
   }
 }
 
+type CallbackOrObserver<T extends (...args: any[]) => any> = T | { next: T };
+
 declare module '@react-native-firebase/auth' {
   // tslint:disable-next-line:no-duplicate-imports required otherwise doesn't work
   import { ReactNativeFirebase } from '@react-native-firebase/app';

packages/auth/lib/index.js

@@ -129,7 +129,14 @@ class FirebaseAuthModule extends FirebaseModule {
     };
   }
 
-  onAuthStateChanged(listener) {
+  _parseListener(listenerOrObserver) {
+    return typeof listenerOrObserver === 'object'
+      ? listenerOrObserver.next.bind(listenerOrObserver)
+      : listenerOrObserver;
+  }
+
+  onAuthStateChanged(listenerOrObserver) {
+    const listener = this._parseListener(listenerOrObserver);
     const subscription = this.emitter.addListener(
       this.eventNameForApp('onAuthStateChanged'),
       listener,
@@ -143,7 +150,8 @@ class FirebaseAuthModule extends FirebaseModule {
     return () => subscription.remove();
   }
 
-  onIdTokenChanged(listener) {
+  onIdTokenChanged(listenerOrObserver) {
+    const listener = this._parseListener(listenerOrObserver);
     const subscription = this.emitter.addListener(
       this.eventNameForApp('onIdTokenChanged'),
       listener,
@@ -157,7 +165,8 @@ class FirebaseAuthModule extends FirebaseModule {
     return () => subscription.remove();
   }
 
-  onUserChanged(listener) {
+  onUserChanged(listenerOrObserver) {
+    const listener = this._parseListener(listenerOrObserver);
     const subscription = this.emitter.addListener(this.eventNameForApp('onUserChanged'), listener);
     if (this._authResult) {
       Promise.resolve().then(() => {

packages/firestore/lib/utils/index.js

@@ -141,6 +141,13 @@ export function parseSetOptions(options) {
 //   };
 // }
 
+function isPartialObserver(input) {
+  if (input == null) {
+    return false;
+  }
+  return input.next != null || input.error != null || input.complete != null;
+}
+
 export function parseSnapshotArgs(args) {
   if (args.length === 0) {
     throw new Error('expected at least one argument.');
@@ -174,20 +181,22 @@ export function parseSnapshotArgs(args) {
   /**
    * .onSnapshot({ complete: () => {}, error: (e) => {}, next: (snapshot) => {} })
    */
-  if (isObject(args[0]) && args[0].includeMetadataChanges === undefined) {
-    if (args[0].error) {
-      onError = args[0].error;
+  if (isObject(args[0]) && isPartialObserver(args[0])) {
+    const observer = args[0];
+    if (observer.error) {
+      onError = isFunction(observer.error) ? observer.error.bind(observer) : observer.error;
     }
-    if (args[0].next) {
-      onNext = args[0].next;
+    if (observer.next) {
+      onNext = isFunction(observer.next) ? observer.next.bind(observer) : observer.next;
     }
   }
 
   /**
    * .onSnapshot(SnapshotListenOptions, ...
    */
-  if (isObject(args[0]) && args[0].includeMetadataChanges !== undefined) {
-    snapshotListenOptions.includeMetadataChanges = args[0].includeMetadataChanges;
+  if (isObject(args[0]) && !isPartialObserver(args[0])) {
+    snapshotListenOptions.includeMetadataChanges =
+      args[0].includeMetadataChanges == null ? false : args[0].includeMetadataChanges;
     if (isFunction(args[1])) {
       /**
        * .onSnapshot(SnapshotListenOptions, Function);
@@ -204,15 +213,16 @@ export function parseSnapshotArgs(args) {
          */
         callback = args[1];
       }
-    } else if (isObject(args[1])) {
+    } else if (isPartialObserver(args[1])) {
       /**
        * .onSnapshot(SnapshotListenOptions, { complete: () => {}, error: (e) => {}, next: (snapshot) => {} });
        */
-      if (isFunction(args[1].error)) {
-        onError = args[1].error;
+      const observer = args[1];
+      if (observer.error) {
+        onError = isFunction(observer.error) ? observer.error.bind(observer) : observer.error;
       }
-      if (isFunction(args[1].next)) {
-        onNext = args[1].next;
+      if (observer.next) {
+        onNext = isFunction(observer.next) ? observer.next.bind(observer) : observer.next;
       }
     }
   }