Fix test to use disableGC option

src/document/crdt/element_rht.ts

@@ -184,6 +184,17 @@ export class ElementRHT {
     return !node.isRemoved();
   }
 
+  /**
+   * `hasByCreatedAt` returns whether the element exists of the given createdAt or not.
+   */
+  public hasByCreatedAt(createdAt: TimeTicket): boolean {
+    const node = this.nodeMapByCreatedAt.get(createdAt.toIDString());
+    if (node == null) {
+      return false;
+    }
+    return !node.isRemoved();
+  }
+
   /**
    * `get` returns the value of the given key.
    */

src/document/crdt/object.ts

@@ -98,6 +98,14 @@ export class CRDTObject extends CRDTContainer {
     return this.memberNodes.has(key);
   }
 
+  /**
+   * `hasByCreatedAt` returns whether the element exists of the given
+   * createdAt or not.
+   */
+  public hasByCreatedAt(createdAt: TimeTicket): boolean {
+    return this.memberNodes.hasByCreatedAt(createdAt);
+  }
+
   /**
    * `toJSON` returns the JSON encoding of this object.
    */

src/document/operation/remove_operation.ts

@@ -69,16 +69,16 @@ export class RemoveOperation extends Operation {
       logger.fatal(`only object and array can execute remove: ${parentObject}`);
     }
     const obj = parentObject as CRDTContainer;
-    const key = obj.subPathOf(this.createdAt);
     // NOTE(chacha912): Handle cases where operation cannot be executed during undo and redo.
     if (
       source === OpSource.UndoRedo &&
       (obj.getRemovedAt() ||
-        (obj instanceof CRDTObject && !obj.has(key!)) ||
+        (obj instanceof CRDTObject && !obj.hasByCreatedAt(this.createdAt)) ||
         (obj instanceof CRDTArray && !obj.get(this.createdAt)))
     ) {
       return;
     }
+    const key = obj.subPathOf(this.createdAt);
     const reverseOp = this.getReverseOperation(obj);
 
     const elem = obj.delete(this.createdAt, this.getExecutedAt());

test/integration/object_test.ts

@@ -587,15 +587,16 @@ describe('Object', function () {
       assert.equal(doc2.toSortedJSON(), '{"color":"red"}');
     });
 
-    it.skip(`Should handle case of reverse operations referencing already garbage-collected elements`, async function ({
+    it(`Should handle case of reverse operations referencing already garbage-collected elements`, async function ({
       task,
     }) {
       interface TestDoc {
         shape: { color: string };
       }
       const docKey = toDocKey(`${task.name}-${new Date().getTime()}`);
-      const doc1 = new Document<TestDoc>(docKey);
-      const doc2 = new Document<TestDoc>(docKey);
+      // TODO(chacha912): Remove the disableGC option
+      const doc1 = new Document<TestDoc>(docKey, { disableGC: true });
+      const doc2 = new Document<TestDoc>(docKey, { disableGC: true });
 
       const client1 = new Client(testRPCAddr);
       const client2 = new Client(testRPCAddr);
@@ -626,12 +627,13 @@ describe('Object', function () {
       assert.equal(doc1.toSortedJSON(), '{"shape":{"color":"red"}}');
       assert.equal(doc2.toSortedJSON(), '{"shape":{"color":"red"}}');
 
-      // TODO(chacha912): fix error that occurs when undoing and make the test pass
       doc1.history.undo();
-      assert.equal(doc1.toSortedJSON(), '{}');
+      assert.equal(doc1.toSortedJSON(), '{"shape":{"color":"red"}}');
+      assert.equal(doc1.getRedoStackForTest().length, 0);
+      assert.equal(doc1.history.canRedo(), false);
       await client1.sync();
       await client2.sync();
-      assert.equal(doc2.toSortedJSON(), '{}');
+      assert.equal(doc2.toSortedJSON(), '{"shape":{"color":"red"}}');
     });
   });
 });