Ionic-framework: Bug: Page transistion error not showing if IonViewCanEnter is used

[shyamal890]

Ionic version: (check one with "x")
[ ] 1.x
[x ] 2.x

I'm submitting a ... (check one with "x")
[x ] bug report
[ ] feature request
[ ] support request => Please do not submit support requests here, use one of these channels: https://forum.ionicframework.com/ or http://ionicworldwide.herokuapp.com/

Current behavior:
Compilation error on a page is not outputted in case IonViewCanEnter is utilized as it only returns true/false. While the developer may be caught unawares and would try to fiddle around with promise in IonViewCanEnter when the error would be somewhere else.

Expected behavior:
IonViewCanEnter should return the promise output.

Steps to reproduce:
http://plnkr.co/edit/ieks9V?p=preview

[jgw96]

Thanks for opening an issue, we will take a look into this.

[dani-digital]

+1. It would be good to have the promise output returned, e.g. when having multiple reasons for rejecting and then appropriately handle it.

[Urbiwanus]

The issue seems to be present in ionic v2.3.0
Discussion can be seen here
https://forum.ionicframework.com/t/uncaught-in-promise-false-when-using-ionviewcanenter/84507/14

[ghost]

Well im glad i didnt update my ionic. My whole App wouldnt work anymore with this issue. Please fix it fast!

[stefanhuber]

Unfortunately, I can confirm this issue. It is not possible to give a negative result with a promise from ionViewCanEnter. It definitely works for me with ionViewCanLeave tough...

[MurhafSousli]

This is pretty old, any updates on this issue?
Currently I found a workaround, I implemented an app guard using viewWillEnter but I am not satisfied with its behavior, it performs many times per navigation, after filtering child pages it performs two times per change!

    this.appCtrl.viewWillEnter
      .filter((page: ViewController) => !page.enableBack())
      .subscribe((page: ViewController) => {

        /** TODO: Check why it performs two times per change */

        /** Check if user is authenticated */
        if (!this.state.authenticated && page.name !== 'AccessPage') {
          this.nav.setRoot('AccessPage');
        }
      });

[joshstrange]

This is also causing issues with our app as well. I don't want the user to navigate away and lose their data without warning first. We return a promise from the ionViewCanLeave and resolve if they say "ok" and reject if they say "cancel". The resolve works fine but the reject throws a:

"Uncaught (in promise) false"

The exact same thing happens with the code in this repo: https://github.com/ionic-team/ionic/blob/efd54750bf44b622a20078be02a2335aabc6dcec/src/components/tabs/test/advanced/pages/tabs-page/tabs.ts#L43

[ionitron-bot[bot]]

Thanks for the issue! This issue is being closed due to inactivity. If this is still an issue with the latest version of Ionic, please create a new issue and ensure the template is fully filled out.

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