Block widget is not focus after drag and drop and undo

[Piotr Jasiun]

1. Open ​http://tests.ckeditor.dev:1030/tests/plugins/widget/manual/block
2. Select any widget.
3. Move it using drag and drop.
4. Undo.

Result: widget is not selected (it should be) and selection is lost.

Bug introduced by #13042.

Note that in #13042 this assertion were removed because they failed:

• ​https://github.com/ckeditor/ckeditor-dev/blob/7342d1806e7534ed14a4ec39d8d5d7b08fd61203/tests/plugins/widget/dnd.js#L380
• ​https://github.com/ckeditor/ckeditor-dev/blob/7342d1806e7534ed14a4ec39d8d5d7b08fd61203/tests/plugins/widget/dnd.js#L388

They should be restored after the fix or appropriate assertion should be added instead.

[Szymon Cofalik]

Fixed on ​branch:t/13129.

I deleted a line of code which should be cleaned in #13042. It is not needed in current implementation of D&D and even introduces bugs. After deleting it, widget is selected after undoing. Tested on all browsers manually.

I also reverted
​https://github.com/ckeditor/ckeditor-dev/blob/7342d1806e7534ed14a4ec39d8d5d7b08fd61203/tests/plugins/widget/dnd.js#L388

However
​​https://github.com/ckeditor/ckeditor-dev/blob/7342d1806e7534ed14a4ec39d8d5d7b08fd61203/tests/plugins/widget/dnd.js#L380
does not really make any sense to me - why we would like to check it there? I moved it before firing the event. This line was there from the beginning of the test.

I also added an extra assert to test if widget is still selected after undo.

[Olek Nowodziński]

• Messages in ​1 and ​2 contradict the actual assertions.
• Assertion

  assert.isTrue( !!editor.getSelection().isFake, ... )
  

  is weak because it will pass no matter which element is selected. What if something else gets selected? Use

  assert.areSame( widget, editor.widgets.focused, 'widget is focused' );
  

  instead. You may need getWidgetById again because undo will demolish editor.widgets and the reference will point to a non–existing widget.

[Szymon Cofalik]

Pushed fixes to ​branch:t/13129

[Olek Nowodziński]

Merged into master in ​git:507dd19.