Cordova pause event error from a null target

[adamdbradley]

Cordova fires a pause event when the app is put into the background, but this error is thrown from within patchViaCapturingAllTheEvents():

It looks as though event.target is null:

This only happens on Cordova's pause event, but is not a problem with the others:
https://cordova.apache.org/docs/en/latest/cordova/events/events.html#pause

[mhevery]

@juliemr could you look at this?

[juliemr]

This is the easy fix: #327

But I haven't found the magical combination of steps necessary to reproduce the bug outside of cordova. @adamdbradley do you have a script to create a targetless event that I can add to our tests without setting up cordova on our CI?

This also doesn't address Zones possibly not properly including or wrapping Cordova's custom events - it just makes sure that it won't outright fail.

[adamdbradley]

@juliemr I dug through cordova and it looks like the pause event ultimately calls fireDocumentEvent

Next, it passes the created evt to documentEventHandlers[type].fire(evt)

Which is cordova's Channel.prototype.fire

The fireArgs variable from within Channel.prototype.fire has the null target:

Channel.prototype.fire then creates and runs each function in the toCall array, use the event with the null target:

One of them being the callback created from within zone's patchViaCapturingAllTheEvents(), which is expecting the event to have a target.

Sorry I'm not able to provide an explanation as to why cordova is calling these events like this, but hopefully this can help document where the issues are coming from, and to help create tests. Hope that helps, thanks.

[juliemr]

Note that this should be fixed (with my dumb fix) in the current version, but I'm leaving this open since we still don't actually have a test to guard against it failing.

[peter-fu]

The error still occurs in iOS simulator for pause event.

exeption nativeEvalAndFetch : TypeError: null is not an object (evaluating 'elt.constructor')

How about making it like this? (I have tried this code locally and there's no error for the pause event any more).

if (elt && elt.constructor) {
  source = elt.constructor['name'] + '.' + onproperty;
} else {
  source = 'unknown.' + onproperty;
}

I'm using Ionic 2 beta, this error can be reproduced in all Ionic 2 beta projects.

$ ionic info

Your system information:

Cordova CLI: 6.1.1
Gulp version:  CLI version 3.9.0
Gulp local:   Local version 3.9.1
Ionic Framework Version: 2.0.0-beta.6-201604261740
Ionic CLI Version: 2.0.0-beta.25
Ionic App Lib Version: 2.0.0-beta.15
ios-deploy version: 1.8.6 
ios-sim version: 5.0.6 
OS: Mac OS X El Capitan
Node Version: v4.3.2
Xcode version: Xcode 7.3.1 Build version 7D1014 

However, I didn't observe such error with the HelloWorld project created by Cordova followed by this article - http://cordova.apache.org/docs/en/latest/guide/cli/index.html. So I am not sure where the root cause of the problem locates.