Improve option insertion and removal algorithms

[josepharhar]

This PR improves the option element insertion and removal steps to incorporate invalid nestings of option elements inside select elements by reusing the nearest ancestor select algorithm. It also adds datalist to the list of disallowed elements for nesting options in.

Fixes #11787

• At least two implementers are interested (and none opposed):
  • Chrome
  • WebKit
• Tests are written and can be reviewed and commented upon at:
  • https://chromium-review.googlesource.com/c/chromium/src/+/7042903
• Implementation bugs are filed:
  • Chromium: https://chromium-review.googlesource.com/c/chromium/src/+/7042903
  • Gecko: …
  • WebKit: https://bugs.webkit.org/show_bug.cgi?id=300317
• Corresponding HTML AAM & ARIA in HTML issues & PRs: Not needed
• MDN issue is filed: Not needed
• The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

---

/form-elements.html ( diff )

[annevk]

I think this works and avoids a lot of the complexity I was envisioning we'd need. Nice!

[annevk]

We also need to account for this where we look for whether option is disabled.

[annevk]

html/semantics/forms/the-select-element/customizable-select/nested-options.tenative.html also needs to be updated.

Here's a proposed patch:

index 0cecdf224b1a..89d5b874704b 100644
--- a/LayoutTests/imported/w3c/web-platform-tests/html/semantics/forms/the-select-element/customizable-select/nested-options.tenative.html
+++ b/LayoutTests/imported/w3c/web-platform-tests/html/semantics/forms/the-select-element/customizable-select/nested-options.tenative.html
@@ -33,6 +33,7 @@ test(() => {
 
 // Manually nest the <options> anyway for the following tests.
 o1.appendChild(o2);
+document.querySelector('select').appendChild(o1);
 
 test(() => {
   assert_equals(select.options.length, 1, 'select.options.length');

[annevk]

Another comment: the moving steps can now call this update algorithm directly. The way this is currently written it'd run a lot of redundant code.

[josepharhar]

html/semantics/forms/the-select-element/customizable-select/nested-options.tenative.html also needs to be updated.

Here's a proposed patch:

Thanks, I am incorporating this into the chromium patch in the PR description.

We also need to account for this where we look for whether option is disabled.

Thanks, I accounted for this and added a test to the WPT changes

Another comment: the moving steps can now call this update algorithm directly. The way this is currently written it'd run a lot of redundant code.

done