bug: listView._startDrag - Uncaught TypeError: Cannot read property 'freeze' of null

[nantunes]

Type: bug

Platform: all

Issue open as requested by @mhartington in #3174 (comment).

PR #3837

Can you provide a detailed description of this issue?
The error ''Uncaught TypeError: Cannot read property 'freeze' of null" appears in the console when dragging an element inside a ion-list item.

How would a robot go about replicating this issue?
I have created a codepen that reproduces the error: http://codepen.io/nantunes/pen/LVLmRJ

Steps to reproduce:
Open the dev tools console and just drag one of the images to the left.

On which platform does this happen occur? (iOS, Android, all, etc.)
On which platform versions does this occur? (Android 4.2, iOS 8, all, etc.)
Tested in Chrome, but probably occurs in all platforms, given the related issue #3174.

Is this an issue with the Ionic Framework or Ionic CLI?
Ionic Framework.

[mhartington]

So the issue is because you do not have an ion-content wrapping the list.
If you wrap the ion-list with the ion-content, the error goes away.
http://codepen.io/mhartington/pen/aOyjYZ

Why this is happening.
This happens because the swipe buttons should prevent scrolling when they are being swiped. So they call a method on the $ionicScrollDelegate. The issue here is that there is no ion-content/$ionicScrollDelegate. So it throws an error.

Your app won't break, but it will just have an error.

[nantunes]

Thanks @mhartington, that solves my problem without keeping a private patch.

But it seems the directive's $ionicScroll require is marked as optional (https://github.com/driftyco/ionic/blob/6c9bc15b2996ae9183624c84a2709fd33f80d20b/js/angular/directive/list.js#L90) and I didn't notice such dependency referred in the docs.

Is it necessary/recommended to always wrap the ion-list or only when enabling swipe?

[nantunes]

Ok, closed PR #3837.