commit 02ef73f562659ed4df9fbf54d2733f43aeb71c5b
author Byungwoo Lee <blee@igalia.com> Fri Oct 21 13:14:16 2022
committer Blink WPT Bot <blink-w3c-test-autoroller@chromium.org> Fri Oct 21 13:21:02 2022
tree 62c3d2d706183f16a99dfb20ea9dff9759ac5681
parent 053b74dd29da1e75b0ab96dedcded9187c50eede

Fix :has() invalidation error when removing an element

The InvalidateAncestorsOrSiblingsAffectedByHas(<parent>, <previous-
sibling>, <flag-for-pseudo-change>) method doesn't traverse to
ancestors for a removed element even if the removed element can
affect the :has() state of a :has() anchor element. These are more
specific conditions of the case:
- there is only one :has() pseudo class (has-child or has-descendant
  relationship) that is tested on the :has() anchor element,
- and the :has() anchor element matched the :has() pseudo class from
  the initial style calculation
- and the removed element has a previous sibling element.

The reason of this bug is the lack of cohesiveness of the logic that
determines the traversal direction for :has() invalidation.

The method gets the :has() invalidation traversal direction from the
affected-by flags (AncestorsOrAncestorSiblingsAffectedByHas,
SiblingsAffectedByHas) of the <previous-sibling> element and starts
the traversal from the element if the <previous-sibling> is not null.

This is based on the assumption that, the previous sibling element
of the mutated element will have the affected-by flags set if the
previous sibling is in the :has() argument testing traversal range.

The assumption is true when the :has() pseudo class have tested on the
:has() anchor element but it didn't matched before, because the
SelectorChecker marks the flags of all the elements in the :has()
argument testing traversal range while testing the :has() argument.

But the assumption cannot be true when the :has() pseudo class have
tested and matched on the :has() anchor element, because the
SelectorChecker stops the :has() argument testing traversal at the
first :has() argument matched element. So, the previous sibling of
the :has() argument matched element doesn't have the flags set.

Currently, the has-descendant relationship invalidation for an
attribute change or pseudo state change works well on the :has()
argument matched element even if the element has a previous sibling
and the previous sibling doesn't have the
AncestorsOrAncestorSiblingsAffectedByHas flag set.

It is because of the conditional argument passing logic in the
Invalidate...AffectedByHas(<changed-element>) method. The method calls
the Invalidate...AffectedByHas(<parent>, <previous-sibling>) with
nullptr as the <previous-sibling> if the <changed-element> doesn't
have the SiblingsAffectedByHas flags set. When the <previous-sibling>
is nullptr, the Invalidate...AffectedByHas(<parent>, <previous-
sibling>, <flag-for-pseudo-change>) method can get the
AncestorsOrAncestorSiblingsAffectedByHas flag from the <parent>.

The problem is that, for insertion or removal, StyleEngine calls the
Invalidate...AffectedByHas(<parent>, <previous-sibling>) without the
conditional argument passing logic. So even if the parent has the
Ancestors...AffectedByHas flag set, the Invalidate...AffectedByHas(
<parent>, <previous-sibling>, <flag-for-pseudo-change>) method
determines the ancestor traversal direction from the flag of the
<previous-sibling>. In case that the <previous-sibling> doesn't have
the flag set, the method will not traverse to ancestors.

This CL added PseudoHasInvalidationTraversalContext class
in StyleEngine so that these logic can be collected within the class:
- logic of determining the :has() invalidation traversal direction
- logic of getting the first element of the traversal

To remove unnecessary method overloading, this is moved to the context
class:
- functionality of passing the flag of indicating whether the :has()
  invalidation is only for the pseudo state change or for all mutation
  types

To fix the bug, this CL adds the missing logic of determining the
traversal direction for the insertion and removal:
- Determine the ancestor traversal direction from the flag of <parent>
  for insertion or removing all children.
- Determine the ancestor traversal direction from the flag of
  <removed-element> for removal

The missing tests are also added:
- unittest to check affected-by flags after removal
- web test to check :has() invalidation after removing non-first
  element.

Bug: 1375248
Change-Id: Ia08bcdfaadf6e8a2973b1b4ba6b640d51e56516c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3960181
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Byungwoo Lee <blee@igalia.com>
Cr-Commit-Position: refs/heads/main@{#1062093}