Race condition in Amplify.Hub signIn handler when using oath

Question

Example code:

Hub.listen('auth', event => {
  const { event: type, data } = event.payload;

  if (type === 'signIn') {
    const session = data.signInUserSession;
    console.log('SESSION', data.signInUserSession);
    setTimeout(() => {
      console.log('SESSION', data.signInUserSession);
    }, 100);
  }
});

When using oath, after the provider redirects to my app, the Hub fires a signIn event. However, the signInUserSession property is null when the event is fired, but gets a value some time later (within 100 ms). This does not seem to occur when using Auth.signIn(email, password) directly; signInUserSession is populated when the event is fired.

What is happening here, and how can I get around it? Currently, I have an explicit delay in the code, which is a terrible hack.

Answer 1

Perhaps the old way of JavaScript for waiting for value to be populated is useful to ensure that code does not fail even if the it takes longer than expected in populating the value.

Here is a sample code that I normally use when no other options are available.

waitForValue(){
    if(myVar!= null && typeof myVar !== "undefined"){
        //value exists, do what you want
        console.log(myVar)
    }
    else{
        setTimeout(() => {this.waitForValue()}, 100);
    }
}

You can refactor this sample code as per your need.

Alternatively, AWS Amplify also have other ways to get current logged in user session. e.g. Auth.currentAuthenticatedUser() and Auth.currentSession() return promise. They can be used like this

private async getUser(){
    let user = null;
    try {
      user = await Auth.currentAuthenticatedUser();
      //console.log(user);
    } catch (err) {
      //console.log(err);
    }
    //return user;
  }