Deprecate jquery.ui.draggable

Why is this issue postponed on the sortable issue? In core.libraries.yml, dialog depends on draggable, but sortable has no dependency on draggable. Is it another missing dependency we should add, or is there another reason it's postponed on sortable as well?

I'd say at this point it's fairly likely we will be developing this issue against D9 soon, especially since there's a lot of risk with the Dialog replacement so Dialog is likely to continue in D9 development as well. (9.0.x opens October 14.)

What about the other uses of draggable? Do we need to do further work on tabledrag after #3064049: Replace jQuery UI sortable with Sortable js?

@bnjmnm confirmed that tabledrag does not actually use draggable. #3064049: Replace jQuery UI sortable with Sortable js proves this (edit: I guess because no HEAD test coverage fails?)

I belatedly realized that core tabledrag predates jQuery UI in core by, like, a lot, so it would not have depended on jquery.ui.draggable unless refactored.

Core library definition:

drupal.tabledrag:
  version: VERSION
  js:
    misc/tabledrag.js: { weight: -1 }
  dependencies:
    - core/jquery
    - core/drupal
    - core/drupalSettings
    - core/jquery.once
    - core/jquery.cookie

(Caveat: we have had missing library dependencies, but in this case it seems unlikely.)

So I guess this can be closed as a duplicate if/when the other issue is committed, and the library added then to the list of those we deprecate.

#8++ … except for the last paragraph. core/jquery.ui.dialog still depends on core/jquery.ui.draggable, so even after #3064049: Replace jQuery UI sortable with Sortable js lands, we'll still need to have #2158943: PP-1 Add a native dialog element using HTMX to deprecate the jQuery UI dialog land before we can do this. Unless you mean #2158943 can deprecate both core/jquery.ui.dialog and core/jquery.ui.draggable?

One of the blockers is in.

I found a way to deprecate this now, see #3113400: Deprecate more jQuery UI library definitions. Unpostponing although we may want to merge into that issue.

Marking duplicate of #3113400: Deprecate more jQuery UI library definitions.