Fix #5654

spec/ParseObject.spec.js

@@ -2068,4 +2068,19 @@ describe('Parse.Object testing', () => {
 
     done();
   });
+
+  it('isNew in cloud code', async () => {
+    Parse.Cloud.beforeSave('CloudCodeIsNew', req => {
+      expect(req.object.isNew()).toBeTruthy();
+      expect(req.object.id).toBeUndefined();
+    });
+
+    Parse.Cloud.afterSave('CloudCodeIsNew', req => {
+      expect(req.object.isNew()).toBeFalsy();
+      expect(req.object.id).toBeDefined();
+    });
+
+    const object = new Parse.Object('CloudCodeIsNew');
+    await object.save();
+  });
 });

spec/rest.spec.js

@@ -446,6 +446,28 @@ describe('rest create', () => {
     });
   });
 
+  it('cannot set id', done => {
+    const headers = {
+      'Content-Type': 'application/json',
+      'X-Parse-Application-Id': 'test',
+      'X-Parse-REST-API-Key': 'rest',
+    };
+    request({
+      headers: headers,
+      method: 'POST',
+      url: 'http://localhost:8378/1/classes/TestObject',
+      body: JSON.stringify({
+        foo: 'bar',
+        id: 'hello',
+      }),
+    }).then(fail, response => {
+      const b = response.data;
+      expect(b.code).toEqual(105);
+      expect(b.error).toEqual('id is an invalid field name.');
+      done();
+    });
+  });
+
   it('test default session length', done => {
     const user = {
       username: 'asdf',

src/RestWrite.js

@@ -52,6 +52,12 @@ function RestWrite(
       'objectId is an invalid field name.'
     );
   }
+  if (!query && data.id) {
+    throw new Parse.Error(
+      Parse.Error.INVALID_KEY_NAME,
+      'id is an invalid field name.'
+    );
+  }
 
   // When the operation is complete, this.response may have several
   // fields.