title: "Developer error: this application is misconfigured" Google sign in on firebase with whitelisted client id
body: <p>I'm trying to migrate to firebase auth on my android app. The package name and SHA1 are currently associated with an old app engine project (which I don't want to upgrade to firebase) and therefore I can't add the SHA1 fingerprint to my new firebase project. The app engine project is currently in production, so I can't remove the android client ids or delete the project. The documentation here <a href="https://support.google.com/firebase/answer/6401008?authuser=0" rel="nofollow noreferrer">https://support.google.com/firebase/answer/6401008?authuser=0</a> says that I should be able to whitelist the client IDs of the old app engine project. However when I do this and then try to log in to the app with google using firebase auth I get the following error <code>"Developer error: this application is misconfigured. Check your SHA1 and package name in the Firebase console."</code> </p>
  
  <p>I have also tried the instructions here <a href="https://firebase.googleblog.com/2016/12/working-with-multiple-firebase-projects-in-an-android-app.html" rel="nofollow noreferrer">https://firebase.googleblog.com/2016/12/working-with-multiple-firebase-projects-in-an-android-app.html</a> which involve passing in a <code>GoogleSignInOptions</code>object into the AuthUI builder with a web client id from the appropriate project like so: </p>
  
  <pre><code>private void StartLoginActivity() {
  
      GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
              .requestIdToken("&lt;my-client-id&gt;.apps.googleusercontent.com")
              .requestEmail()
              .build();
  
      List&lt;AuthUI.IdpConfig&gt; providers = Arrays.asList(
              new AuthUI.IdpConfig.EmailBuilder().build(),
              new AuthUI.IdpConfig.GoogleBuilder().setSignInOptions(gso).build());
  
      startActivityForResult(
              AuthUI.getInstance()
                      .createSignInIntentBuilder()
                      .setAvailableProviders(providers)
                      .build(),
              RC_SIGN_IN);
  }
  </code></pre>
  
  <p>but when I do that I get the error <code>java.lang.IllegalArgumentException: two different server client ids provided</code></p>
  
  <p>So my question is how can I configure my firebase project to enable auth when the SHA1 is associated with an existing GCP project?</p>