UndoManager configuration to filter deletes

tests/undo-redo.tests.js

@@ -172,7 +172,7 @@ export const testUndoEvents = tc => {
 export const testTrackClass = tc => {
   const { users, text0 } = init(tc, { users: 3 })
   // only track origins that are numbers
-  const undoManager = new UndoManager(text0, new Set([Number]))
+  const undoManager = new UndoManager(text0, { trackedOrigins: new Set([Number]) })
   users[0].transact(() => {
     text0.insert(0, 'abc')
   }, 42)
@@ -201,3 +201,22 @@ export const testTypeScope = tc => {
   undoManagerBoth.undo()
   t.assert(text1.toString() === '')
 }
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testUndoDeleteFilter = tc => {
+  /**
+   * @type {Array<Y.Map<any>>}
+   */
+  const array0 = /** @type {any} */ (init(tc, { users: 3 }).array0)
+  const undoManager = new UndoManager(array0, { deleteFilter: item => !(item instanceof Y.Item) || (item.content instanceof Y.ContentType && item.content.type._map.size === 0) })
+  const map0 = new Y.Map()
+  map0.set('hi', 1)
+  const map1 = new Y.Map()
+  array0.insert(0, [map0, map1])
+  undoManager.undo()
+  t.assert(array0.length === 1)
+  array0.get(0)
+  t.assert(Array.from(array0.get(0).keys()).length === 1)
+}