add doc parameter to UndoManager

tests/undo-redo.tests.js

@@ -49,6 +49,20 @@ export const testUndoText = tc => {
   t.compare(text0.toDelta(), [{ insert: 'b' }, { insert: 'cxy', attributes: { bold: true } }, { insert: 'z' }])
 }
 
+/**
+ * Test case to fix #241
+ * @param {t.TestCase} tc
+ */
+export const testEmptyTypeScope = tc => {
+  const ydoc = new Y.Doc()
+  const um = new Y.UndoManager([], { doc: ydoc })
+  const yarray = ydoc.getArray()
+  um.addToScope(yarray)
+  yarray.insert(0, [1])
+  um.undo()
+  t.assert(yarray.length === 0)
+}
+
 /**
  * Test case to fix #241
  * @param {t.TestCase} tc