zone.js promises returning Unhandled Promise Rejection error even with catch blocks

I am working on an angular environment with zone.js so all the native es6 promises have been over-written by zone-aware promises. I have 2 functions called save() and onSaveCb()

save() calls a function called validate() which gets the error-codes of any of the saved objects already present in the file so it is done in sync.

if hasError() returns true we return Promise.reject() from save() otherwise we send a save request to the backend.

Now, onSaveCb() function is an async/await function which has a try-catch block around save().

Problem:

When Promise is rejected from save() function, I see console log error:

zone.js:682 Unhandled Promise rejection: ; Zone: ; Task: onClick Event ; Value: Error:

I tried a bunch of things with wrapping the function save in a promise and then rejecting it, but i still see the same error

function save() {
   let errorCode = this.validate(); // This is a sync call
   if(errorCode !== 0) { return Promise.reject(errorCode);}
   return https(url).then(function() {return true});
} 

function async onSaveCb() {
   try{
     let response = await this.save();
     alertUI(response);
     } catch (response) {
       alertUI(response);
     }
}

I am not sure why I am getting this message when I have clearly written error handling in the catch block. Any help here would be helpful

@utsavkapoor

@utsavkapoor thanks for posting the issue, I will check it.

@utsavkapoor

@utsavkapoor, could you provide a sample repo to reproduce, thanks!

copy this inside an empty chrome window.
or open it here: https://codepen.io/kanti/pen/yLBPLGB?editors=0011
or here: https://jsfiddle.net/iKanti/b67zu4pq/1/

Without zone.js it doesn't throw an Unhandled Promise rejection.
But with zone.js it throws an Unhandled Promise rejection.

function x() {
  return Promise.reject(new Error('Expired Token'))
}
(async function() {
  await x();
})().catch(console.warn);
// the above code will print no:
// 'Unhandled Promise rejection: Expired Token ; Zone: <root> ; Task: null ; Value: Error: Expired Token'
// but the code below will:
import('https://unpkg.com/zone.js').then(() => {
  (async function() {
    await x();
  })().catch(console.warn);
});

@Kanti

@Kanti, sure, I have fixed this one, but it break some cases inside Google, so I am working on to provide an option flag to enable/disable this uncaught promise error feature of zone.js.

Is there any update on this issue? I'm seeing warnings about promises I actually catch as well (using promise.then(x => { }, err => { })). I don't want to totally disable Zone's uncaught promise detection feature -- it would be great if it worked! -- but I'd like it to stop spuriously telling me I didn't catch something that is in fact caught.

this issue should be fixed by this PR #35873

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zone.js promises returning Unhandled Promise Rejection error even with catch blocks #31680

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zone.js promises returning Unhandled Promise Rejection error even with catch blocks #31680

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JiaLiPassion commented on Jun 19, 2019

JiaLiPassion commented on Jul 19, 2019

Kanti commented on Sep 3, 2019

JiaLiPassion commented on Sep 5, 2019

thw0rted commented on Jan 29, 2020

JiaLiPassion commented on May 28, 2020

angular-automatic-lock-bot commented on Jun 28, 2020

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