Angular / Ionic mobile app ios does not fetch from Firebase using angularfire

import { initializeApp } from 'firebase/app';
import { getFirestore } from 'firebase/firestore';
import { Capacitor } from '@capacitor/core';
import { initializeAuth, indexedDBLocalPersistence } from 'firebase/auth';
import { getAuth } from 'firebase/auth';

const firebaseApp = initializeApp({
 apiKey: process.env.VUE_APP_FIREBASE_API_KEY,
 authDomain: process.env.VUE_APP_FIREBASE_AUTH_DOMAIN,
 databaseURL: process.env.VUE_APP_FIREBASE_DATABASE_URL,
 projectId: process.env.VUE_APP_FIREBASE_PROJECT_ID,
 storageBucket: process.env.VUE_APP_FIREBASE_STORAGE_BUCKET,
 messagingSenderId: 
 process.env.VUE_APP_FIREBASE_MESSAGING_SENDER_ID,
 appId: process.env.VUE_APP_FIREBASE_APP_ID,
});


function whichAuth() {
  let auth
  if (Capacitor.isNativePlatform()) {
    auth = initializeAuth(firebaseApp, {
      persistence: indexedDBLocalPersistence
    })
  } else {
    auth = getAuth()
  }
  return auth
}

export const auth = whichAuth()
const db = getFirestore();

export const auth = whichAuth();
export { firebaseApp, db };

Then in your component, cal your method like this await signInAnonymously(auth);. Don't forget to import the auth we exported at the top.

TL;DR: in capacitor.config set server: { iosScheme: "ionic" }

It looks like the issue is Firebase incorrectly detecting the environment (see @alistairheath's comment here).

There's a check in the auth/compat library here which checks for the URL scheme "ionic://", which was used by older versions of Capacitor (it's now "capacitor://") and if you set it back to "ionic://" (see the config option iosScheme) it seems to work again and doesn't attempt to load the gapi libraries.

Been struggling a lot with this issue too but I managed to fix it. For those who need help here's my code.

You can delete all Firebase related imports from app.module.ts since this solution only uses Firebase. The packages rxfire and @angular/fire can be removed from your package.json. The only dependency I have is "firebase": "^9.6.1". I used observables for the getObject and list functions since that's what I'm used to and I didn't want to rewrite my original code.

import { Injectable } from '@angular/core';
import { Capacitor } from '@capacitor/core';
import { environment } from '@environment';
import { initializeApp } from 'firebase/app';
import { Auth, getAuth, indexedDBLocalPersistence, initializeAuth, signInWithCustomToken } from 'firebase/auth';
import { Database, getDatabase, onValue, orderByChild, query, ref } from 'firebase/database';
import { Observable, Observer, from } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class FirebaseService {
  private readonly database: Database;
  private readonly auth: Auth;

  constructor() {
    const firebaseApp = initializeApp(environment.firebase);

    if (Capacitor.isNativePlatform()) {
      initializeAuth(firebaseApp, {
        persistence: indexedDBLocalPersistence
      });
    }

    this.database = getDatabase(firebaseApp);
    this.auth = getAuth(firebaseApp);
  }

  connectFirebase(firebaseToken) {
    return from(signInWithCustomToken(this.auth, firebaseToken));
  }

  disconnectFirebase() {
    return from(this.auth.signOut());
  }

  getObject<T>(path: string): Observable<T> {
    return new Observable((observer: Observer<T>) => {
      const dbRef = ref(this.database, path);
      const listener = onValue(dbRef, snapshot => {
        const data = snapshot.val();
        observer.next(data);
      });

      return {
        unsubscribe() {
          listener();
        }
      };
    });
  }

  public list<T>(path: string, orderChildBy?: string): Observable<Array<T>> {
    return new Observable<Array<T>>((observer: Observer<Array<T>>) => {
      const dbRef = ref(this.database, path);
      const dbReference = !orderChildBy ? dbRef : query(dbRef, orderByChild(orderChildBy));

      const listener = onValue(dbReference, snapshot => {
        const data = Object.values<T>(snapshot.val() || {});
        console.log(path, data);
        observer.next(data);
      });

      return {
        unsubscribe() {
          listener();
        }
      };
    });
  }
}

For those who can't see the error message thrown by firebase try the following command in your Safari console to see the error.

window.location.reload()

The real problem: firebase-js-sdk on mobile iOS assumes google API (gapi) exists on the window, even when it isn't used.

I found a work around: Mock window.gapi before using firebase auth login:

window['gapi'] = {
  load: (name: string) => Promise.resolve(),
  iframes: {
    getContext: () => {
      return {
        iframe: {
          contentWindow: {
            postMessage: (message: any) => {
              console.log("gapi iframe message:", message);
            }
          }
        }
      }
    }
  }
} as any;