Create initial implementation

[ma2ciek]

Overview created by @pjasiun:

• The editor created using watchdog will be automatically observed and restarted in case of a fatal error.
• The watchdog will save the editor data in a similar way autosave plugin do. Then, when the editor is restarted these data will be used as new initial data. Note that if the user uses RTC it should not be an issue because the editor will use data from the collaboration server anyway.
• When the CKEditorError will occur it might be tricky to guess which editor causes the issue, the error could be thrown on the model class which knows nothing about the editor instance. However, since watchdog keeps the instance of the editor, it can recursively iterate over its own properties and check if the error is thrown on any of it.

Full usage:

const watchdog = new Watchdog();
watchdog.setCreator( ( element, config ) => ClassicEditor.create( element, config ) );
watchdog.setDestructor( editor => editor.destroy() );
		
watchdog.create( element, config );

Shortcut:

const watchdog = Watchdog.for( ClassicEditor );
watchdog.create( element, config );

Additional API:

watchdog.editor;
		
watchdog.destroy();
watchdog.restart();
		
watchdog.on( 'restart', () => { console.log( 'restarted' ); } )

[ma2ciek]

Should we be aware of such usage?

watchdog.create( element, config );

// Immediately called (until the editor is fully initialized):
watchdog.destory();

IMO yes, we should stack actions so the editor will be destroyed once it's created.

cc @pjasiun.

[pjasiun]

IMO yes, we should stack actions so the editor will be destroyed once it's created.

I think the editor could support it. If the editor does not support it, then watchdog should not add such functionally (as long as there is no special reason, valid for Watchdog, but not for the editor, why Watchdog should have such functionality).

[ma2ciek]

The watchdog has a slightly different API. Using the editor you can't do the above because you don't have access to the editor before the initialization.

[pjasiun]

Right. Then, I think we could add such protection, but we can do it in the follow-up.