colgroup and col elements are removed from markup when configured as allowed in GHS

[ericgsmith]

📝 Provide detailed reproduction steps (if any)

When specifying col and colgroup elements as allowed for General HTML support they are being removed if the Table plugin is enabled but the TableResize plugin is not.

See the MR #15573 - manual test "table-no-resize"

✔️ Expected result

Expected result is the the col and colgroup elements remain in the HTML.

❌ Actual result

View HTML does not contain the col and colgroup elements.

The model does contain the HTML - but this is not rendered when the table is.

In the inspector for the table-resize test I can see 2 schema definitions for col and colgroup:

htmlCol / htmlColgroup and the tableColumn / tableColumnGroup definitions:

The tableColumn / tableColumnGroup definitions are missing the allowedIn: table definition.

In the model the HTML is showing as htmlCol and htmlColgroup - but this is not allowed in the table schema - so nothing is rendered in the view.

❓ Possible solution

Unsure of the solution - seems like only 1 schema should exist and it should have all the information needed to be retained.

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[Witoso]

The GHS doesn't support empty elements right now:

ckeditor5/packages/ckeditor5-html-support/src/schemadefinitions.ts

Lines 21 to 28 in 4bbcdaa

	// Skipped elements due to lack empty element support:
	// * hr
	// * area
	// * br
	// * command
	// * map
	// * wbr
	// * colgroup -> col

[wimleers]

@Witoso But <colgroup> isn't an empty element? <col> is indeed.

[wimleers]

Drupal.org issue: https://www.drupal.org/project/drupal/issues/3397556

[Witoso]

I assume there's some relation there that blocked us, maybe @niegowski could share more here.

[ericgsmith]

Hi there - sorry for the delay on this - it looks like support was added in #13328 but just the docs are out of date?

I should have been clearer in the description that GHS does work for col and colgroup elements when:

✅ - the TableResize plugin is enabled or
✅ - Table plugin is not enabled -

❌ it does not work in the scenario where Table is enabled but TableResize is not.

[ericgsmith]

Ok - I have added #15573 to

• extend table, ghs-all-features and ghs-no-features manual tests to show the elements are supported in certain circumstances
• add manual test fortable-resize to show where its not working

Updated issue description with a better explanation - initial issue description wasn't clear as I had no idea what I was look at 🙈

I don't know if I can commit additional time to fix - but if somebody can suggest where this can be fixed I can certainly try where I can. Other step would be removing the comment that implies this element has no support

[Witoso]

@filipsobol would be great if you could take a look!