[lexical] Bug Fix: Skip $reconcileChildren fast path during full reconcile#8564
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…ncile (facebook#8563) The sizeDelta===0 children fast path walks from prevElement.__first while following the next node map's __next pointers, assuming prev and next children share the same keys in the same order. It gated that assumption on _cloneNotNeeded, but a FULL_RECONCILE (setEditorState, which backs history undo/redo) swaps the node map wholesale without routing changes through getWritable(), leaving _cloneNotNeeded empty even when children differ by key. Undoing a markdown code-block transform produces a same-size child key swap, so the walk reached a next-only key and threw "reconcileNode: prevNode or nextNode does not exist in nodeMap" during reconciliation. Gate the fast path on !treatAllNodesAsDirty so full reconciles fall through to the general key-diffing path. https://claude.ai/code/session_01EAeZ6geVH74SpUrRhY6Z8h
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Manage the editor lifecycle with `using` and move root-element setup/teardown into a test extension's register function (setRootElement + document.body cleanup), matching the idiom used by the other reconciler repro tests. The editor's dispose also calls setRootElement(null), so the whole fixture tears down at end of scope without an afterEach. https://claude.ai/code/session_01EAeZ6geVH74SpUrRhY6Z8h
…#8563 repro A detached root element is enough to drive DOM reconciliation for this repro (the crash is in node-map lookups, not layout), so set it inline and let the `using` editor's dispose call setRootElement(null). Removes the test extension and document.body bookkeeping. https://claude.ai/code/session_01EAeZ6geVH74SpUrRhY6Z8h
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approved these changes
May 26, 2026
This was referenced May 26, 2026
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Description
The sizeDelta===0 children fast path walks from prevElement.__first while following the next node map's __next pointers, assuming prev and next children share the same keys in the same order. It gated that assumption on _cloneNotNeeded, but a FULL_RECONCILE (setEditorState, which backs history undo/redo) swaps the node map wholesale without routing changes through getWritable(), leaving _cloneNotNeeded empty even when children differ by key. Undoing a markdown code-block transform produces a same-size child key swap, so the walk reached a next-only key and threw "reconcileNode: prevNode or nextNode does not exist in nodeMap" during reconciliation.
Gate the fast path on !treatAllNodesAsDirty so full reconciles fall through to the general key-diffing path.
Closes #8563
Test plan
New unit tests