FR: please add function Auth.getCurrentUser() as a promise that will return current user or null

[Thaina]

• Firebase SDK version: 4.9.0
• Firebase Product: auth

Auth.currentUser object is unreliable to get user from persistence storage. If the authentication system could be pending and don't really have ensure finishing endpoint then you should have a promise for it

So I want to have promise function Auth.getCurrentUser() in addition to onAuthStateChange that would eventually return user but would return null if no user exist in persistence storage or user require sign in from expired token

[google-oss-bot]

Hmmm this issue does not seem to follow the issue template. Make sure you provide all the required information.

[bojeil-google]

You can easily implement that on your own with a couple of lines:

function getCurrentUser(auth) {
  return new Promise((resolve, reject) => {
     const unsubscribe = auth.onAuthStateChanged(user => {
        unsubscribe();
        resolve(user);
     }, reject);
  });
}

[Thaina]

@bojeil-google If the user does not signed in will that promise would ever fired for null?

And I think this function is really common enough to included in the SDK

[bojeil-google]

Yes that promise will fire. onAuthStateChanged always triggers with the initial state even when it is null. That is what you care for here, the current state. After that is determined, you unsubscribe.

[Thaina]

I see but anyway if it really just a couple line and will be the same for everyone so why it not be inside SDK. Did you not consider it useful?

And also that function would fire only one time at first call and will not fire again in second call am I right? What I want from getCurrentUser() function is consistently return null if it already checking in persistence storage, or return the actual current user after that

At least it should have a function like getPreparedAuthStated() or isPreparedAuthFinished

[bojeil-google]

I have no idea what you mean by: " consistently return null if it already checking in persistence storage, or return the actual current user after that".

[Thaina]

@bojeil-google If I don't misunderstand, the onAuthStateChanged in promise function you present will work only on the first call. If I call that function on the second time it will never return because the auth state never change again after that

This is not what I want from getCurrentUser(). I want this function to actively checking that user is not really signed in before. I want it to be promise just in case that firebase auth does not finish initializing yet, in that case the user was signed in before but firebase itself are not ready. So return promise is better solution

What I want is

• If called when firebase auth preparation is not finished : return promise to wait
  • after preparation finished but user was not signed in before : resolve null from the promise
  • after preparation finished and user was signed in before : resolve currentUser from the promise
• If called after firebase auth preparation is finished
  • but user is not signed in : immediately resolve null from the promise
  • and user is signed in : immediately resolve currentUser from the promise

I want this consistence behavior for getCurrentUser() function

But if I don't misunderstand, the function you present will never resolve if that function was called after firebase auth preparation is finished unless the user try to signed in

[Thaina]

If I misunderstand above, which means onAuthStateChanged will always fire once whenever it get called for the current user without the need of signIn or signOut action. Then I would like to request that this behavior should be mentioned in the document

[bojeil-google]

Please read the documentation, you presume some incorrect assumptions.
If we were to implement a promise that returns the current user, it will be done as I described.
onAuthStateChanged will always trigger every time it is set. It is super easy to test that.
If it is called while Auth is still initializing and loading state, it will wait for it to complete before resolving. If you call it after, it will still trigger immediately with the current user.

If you want some custom function or listener that triggers based on your own custom requirements, we provide all the APIs you need to build that.

If you are experiencing issues with the behavior of onAuthStateChanged listener, please file the bugs and we will make sure to address them.

[Thaina]

@bojeil-google I know that if I call onAuthStateChanged before initializing and loading state it would be triggered. However I read the document and haven't seen mentioning about what happen if I register onAuthStateChanged after it finished initializing and loading state but the user is not signed in yet

I know that it would be surely be triggered whenever user would sign in by any means. But if user never sign in at all would it trigger that it change from null to null?

Why is that?

Is it changed from null as auth not initialized to null as user not signed in ?

And if I register onAuthStateChanged after finished initialized why it still trigger when user AuthState was not changed at all?

In the document

https://firebase.google.com/docs/reference/js/firebase.auth.Auth

I have seen the explanation only these

Adds an observer for changes to the user's sign-in state.

Prior to 4.0.0, this triggered the observer when users were signed in, signed out, or when the user's ID token changed in situations such as token expiry or password change. After 4.0.0, the observer is only triggered on sign-in or sign-out.

At this line

the observer is only triggered on sign-in or sign-out

is very pinpoint that if user not doing any signin/signout at all it should not be triggered just from registering the observer

Also in here is not mention about that too

https://firebase.google.com/docs/auth/web/manage-users

What document you think I should read?

[Thaina]

@bojeil-google Do you have a link to the document you mention about this behavior?

[bojeil-google]

This is the reference for onAuthStateChanged:
https://firebase.google.com/docs/reference/js/firebase.auth.Auth#onAuthStateChanged

This is the guide on how to use it:
https://firebase.google.com/docs/auth/web/manage-users#get_the_currently_signed_in_user

Any time you call this listener after initial state has been determined, it will trigger with the current state (null if no user signed in, and with a user if a user is signed in). If you don't believe, then just try it out yourself.

[Thaina]

@bojeil-google It not that I would not belief but it the API name itself is misleading so I got confused. I test it and it seem the real behavior is like you stated. But because it not mentioned in the document I don't know I should rely on it or not

That's why I said if I misunderstand then it should be documented about this behavior. Because the API name is "onAuthStateChanged" but it will also firing one time when the auth state not really changed