Fix #2056

Author: mstniy

integration/test/ParseRelationTest.js

@@ -43,6 +43,34 @@ describe('Parse Relation', () => {
       });
   });
 
+  it('can do consecutive adds (#2056)', done => {
+    const ChildObject = Parse.Object.extend('ChildObject');
+    const childObjects = [];
+    for (let i = 0; i < 2; i++) {
+      childObjects.push(new ChildObject({ x: i }));
+    }
+    const parent = new Parse.Object('ParentObject');
+    parent.save().then(parentAgain => {
+      Parse.Object.saveAll(childObjects)
+        .then(() => {
+          for (const child of childObjects) {
+            parentAgain.relation('child').add(child);
+          }
+          return parentAgain.save();
+        })
+        .then(() => {
+          return parentAgain.relation('child').query().find();
+        })
+        .then(results => {
+          assert.equal(results.length, 2);
+          const expectedIds = new Set(childObjects.map(r => r.id));
+          const foundIds = new Set(results.map(r => r.id));
+          assert.deepEqual(expectedIds, foundIds);
+          done();
+        });
+    });
+  });
+
   it('can query relation without schema', done => {
     const ChildObject = Parse.Object.extend('ChildObject');
     const childObjects = [];

src/ParseRelation.js

@@ -50,12 +50,9 @@ class ParseRelation {
         if (this.parent.id !== parent.id) {
           throw new Error('Internal Error. Relation retrieved from two different Objects.');
         }
-      } else if (parent.id) {
-        this.parent = parent;
       }
-    } else {
-      this.parent = parent;
     }
+    this.parent = parent;
   }
 
   /**