`_accept` collapsed every non-ACCEPT filter result into a single boolean,
so FILTER_REJECT behaved exactly like FILTER_SKIP: the node was not
returned, but the walk still descended into its subtree. Per DOM 6.1,
FILTER_REJECT rejects a node *and* its descendants.
This was unreachable until #440 exposed the real NodeFilter constants,
which made the canonical prune idiom
if (node.tagName === 'SCRIPT') return NodeFilter.FILTER_REJECT;
start yielding nodes from inside the pruned subtree instead of failing
loudly — sanitizers and text extractors built on TreeWalker silently got
extra content.
Split the filter into a three-valued `_filter` (keeping `_accept` as the
boolean wrapper the sibling/child movers use) and give nextNode a second
traversal step for the reject case. That step lives in the DOM layer as
`DomTree::next_after_subtree`, mirroring how #447 put `next_in_subtree`
there: both share the ancestor climb, and REJECT costs no more JS/native
crossings than SKIP.
NodeIterator shares this walker but has no subtree pruning (DOM 6.2:
FILTER_REJECT behaves as FILTER_SKIP), so `createNodeIterator` marks the
walker `_rejectIsSkip` and keeps the plain step. Covered by its own test
so the shared implementation cannot drift.
Andrey Mnatsakanov
1a5c27a592