LiveQuery handle unset operation (#714)

* LiveQuery handle unset operation

* change logic to original object

* Nit

Author: dplewis

src/LiveQueryClient.js

@@ -389,17 +389,22 @@ class LiveQueryClient extends EventEmitter {
       break;
     default: {
       // create, update, enter, leave, delete cases
-
-      // Does not override / clear server data
-      delete data.object.__type;
-      const parseObject = ParseObject.fromJSON(data.object, false);
       if (!subscription) {
         break;
       }
       if (data.original) {
         delete data.original.__type;
+        // Check for removed fields
+        for (const field in data.original) {
+          if (!(field in data.object)) {
+            data.object[field] = undefined;
+          }
+        }
         data.original = ParseObject.fromJSON(data.original, false);
       }
+      delete data.object.__type;
+      const parseObject = ParseObject.fromJSON(data.object, false);
+
       subscription.emit(data.op, parseObject, data.original);
     }
     }

src/__tests__/LiveQueryClient-test.js

@@ -264,6 +264,45 @@ describe('LiveQueryClient', () => {
     expect(isChecked).toBe(true);
   });
 
+  it('can handle WebSocket response unset field', async () => {
+    const liveQueryClient = new LiveQueryClient({
+      applicationId: 'applicationId',
+      serverURL: 'ws://test',
+      javascriptKey: 'javascriptKey',
+      masterKey: 'masterKey',
+      sessionToken: 'sessionToken'
+    });
+    // Add mock subscription
+    const subscription = new events.EventEmitter();
+    liveQueryClient.subscriptions.set(1, subscription);
+
+    const object = new ParseObject('Test');
+    const original = new ParseObject('Test');
+    const pointer = new ParseObject('PointerTest');
+    pointer.id = '1234';
+    original.set('pointer', pointer);
+    const data = {
+      op: 'update',
+      clientId: 1,
+      requestId: 1,
+      object: object._toFullJSON(),
+      original: original._toFullJSON(),
+    };
+    const event = {
+      data: JSON.stringify(data)
+    }
+    let isChecked = false;
+    subscription.on('update', (parseObject, parseOriginalObject) => {
+      isChecked = true;
+      expect(parseObject.toJSON().pointer).toBeUndefined();
+      expect(parseOriginalObject.toJSON().pointer.objectId).toEqual(pointer.id);
+    });
+
+    liveQueryClient._handleWebSocketMessage(event);
+
+    expect(isChecked).toBe(true);
+  });
+
   it('can handle WebSocket close message', () => {
     const liveQueryClient = new LiveQueryClient({
       applicationId: 'applicationId',