UndoManager: fix special deletion case. closes #447 closes #443

src/structs/Item.js

@@ -211,11 +211,6 @@ export const redoItem = (transaction, item, redoitems, itemsToDelete, ignoreRemo
       while (left !== null && left.redone !== null) {
         left = getItemCleanStart(transaction, left.redone)
       }
-      // check wether we were allowed to follow right (indicating that originally this op was replaced by another item)
-      if (left === null || /** @type {AbstractType<any>} */ (left.parent)._item !== parentItem) {
-        // invalid parent; should never happen
-        return null
-      }
       if (left && left.right !== null) {
         // It is not possible to redo this item because it conflicts with a
         // change from another client

tests/undo-redo.tests.js

@@ -602,3 +602,32 @@ export const testBehaviorOfIgnoreremotemapchangesProperty = tc => {
   t.assert(map1.get('x') === 2)
   t.assert(map2.get('x') === 2)
 }
+
+/**
+ * Special deletion case.
+ *
+ * @see https://github.com/yjs/yjs/issues/447
+ * @param {t.TestCase} tc
+ */
+export const testSpecialDeletionCase = tc => {
+  const origin = 'undoable'
+  const doc = new Y.Doc()
+  const fragment = doc.getXmlFragment()
+  const undoManager = new Y.UndoManager(fragment, { trackedOrigins: new Set([origin]) })
+  doc.transact(() => {
+    const e = new Y.XmlElement('test')
+    e.setAttribute('a', '1')
+    e.setAttribute('b', '2')
+    fragment.insert(0, [e])
+  })
+  t.compareStrings(fragment.toString(), '<test a="1" b="2"></test>')
+  doc.transact(() => {
+    // change attribute "b" and delete test-node
+    const e = fragment.get(0)
+    e.setAttribute('b', '3')
+    fragment.delete(0)
+  }, origin)
+  t.compareStrings(fragment.toString(), '')
+  undoManager.undo()
+  t.compareStrings(fragment.toString(), '<test a="1" b="2"></test>')
+}