Ckeditor5: [Chrome, Edge] Exception after pressing CTRL + U while content is selected

[Mgsy]

🐞 Is this a bug report or feature request? (choose one)

• Bug report

💻 Version of CKEditor

1.0.0-alpha2

📋 Steps to reproduce

Scenario 1

1. Go to http://localhost:8125/ckeditor5-core/tests/manual/article.html.
2. Select the image caption.
3. Press Ctrl + U (it's still Ctrl in MacOS).

Scenario 2

1. Go to http://localhost:8125/ckeditor5-core/tests/manual/article.html.
2. Select two list items.
3. Press Ctrl + U (it's still Ctrl in MacOS).

✅ Expected result

Nothing happens.

❎ Actual result

There is the error in the console and in Chrome the selection has moved to the beginning of the document.

📃 Other details that might be useful

Error

input.js:205 Uncaught TypeError: modelFromCurrentDom.getChildren is not a function
    at MutationHandler._handleContainerChildrenMutations (input.js:205)
    at MutationHandler.handle (input.js:147)
    at Input._handleMutations (input.js:105)
    at Document.listenTo (input.js:50)
    at Document.fire (emittermixin.js:269)
    at MutationObserver._onMutations (mutationobserver.js:248)

GIF

Notes

It doesn't occur if the underline plugin is loaded.

Other information

OS: Windows 10, MacOS X
Browser: Chrome, Edge

[Reinmar]

This is a good one. I guess that a native underline comes into action and breaks our mutation observer.

[scofalik]

I wonder what's up, cause I can't reproduce it, while @Mgsy says that it is fixed for caption but still crashes for list items.

EDIT: Okay, yeah, whatever, as usual it suddenly started to be broken for me aswell, but just after writing a comment.

[scofalik]

Although, when I click Cmd + U, I don't get an underline, instead I get this sign: ¨ and composition starts (I guess) and this crashes when there is a multielement selection.

[Reinmar]

BTW, on my MacOS at least, with Polish Pro keyboard the keystroke which is worth testing is Alt+U.

Pressing Alt+U enters umlaut composition. So Alt+U,U inserts "ü". This works fine on Firefox and Chrome in some cases now, but crashes on the two-lists-item-selection. After #140 it simply stops crashing in the two-lists-item-selection case, but it will do nothing in Chrome (in FF, it works fine). Which is fine for now. Let's see if anyone will ever report it.

[scofalik]

Did you check if other keystrokes (Cmd+U, Ctrl+U) crash the editor?

[Reinmar]

I tried all combinations with U. For some reason Ctrl+U crashes the editor on master, but at the same time, this keystroke has no action even here, in a textarea or in CKEditor 4.