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onAuthStateChange called on first user token refresh and it should not happen #5685

@acanimal

Description

@acanimal

Hi,
I started as a tech question in stackoverflow but it seems it is a bug

[REQUIRED] Describe your environment

  • Operating System version: macosx
  • Browser version: chrome 95
  • Firebase SDK version: 9.2.0, 9.1.3
  • Firebase Product: auth

[REQUIRED] Describe the problem

As doc explains onAuthStateChange should be called only on signin and signout actions. It seems the listener is also called on the first user token refresh.

Steps to reproduce:

<html>
  <script src="https://www.gstatic.com/firebasejs/9.1.3/firebase-app-compat.js"></script>
  <script src="https://www.gstatic.com/firebasejs/9.1.3/firebase-auth-compat.js"></script>
  <script>
    // Initialize Firebase
    const config = {
      apiKey: '',
      authDomain: '',
      databaseURL: '',
      projectId: '',
      storageBucket: '',
      messagingSenderId: '',
      appId: '',
    };
    const email = "[email protected]";
    const pass = "123456abc";
    const app = firebase.initializeApp(config);
    const auth = app.auth();

    const example = async () => {
      auth.onAuthStateChanged(async (user) => {
        console.log('onAuthStateChanged user uid', user ? user.uid : 'null');

        if (!user) {
          try {
            await auth.createUserWithEmailAndPassword(email, pass);
          } catch (e) {
            console.log('user already created');
          }

          console.log('signin')
          await auth.signInWithEmailAndPassword(email, pass);
        }
      })

      setInterval(() => {
        console.log('force token renewal');
        auth.currentUser.getIdToken(true);
      }, 5000)
    };

    example();
  </script>
</html>

The output

If you run for the first time or if there is no session you get the output:

onAuthStateChanged user uid null   <-- becuase there is no session stored
user already created
signin
onAuthStateChanged user uid mqLHdtQhwJPaXqIEbDqFBwFoxLz1 <-- this is because the signin
force token renewal <-- run each 5 secs

Having a session stored if you refresh the page you find the next output:

onAuthStateChanged user uid mqLHdtQhwJPaXqIEbDqFBwFoxLz1 <-- recover the session
force token renewal
onAuthStateChanged user uid mqLHdtQhwJPaXqIEbDqFBwFoxLz1 <-- run again after refresh token
force token renewal <-- subsequent refresh token doesn not cause a call to onAuthStateChange

The problem is with the first refresh of token. After debugging a bit in chrome I found that on the first token refresh the function notifyAuthListeners() from the file auth_impl.ts is invoked but the variable this.lastNotifiedUid is undefined which causes the refresh to be notified also to onAuthStateChange listeners.

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