Fix issue #5274 on RestQuery.each and relations

spec/RestQuery.spec.js

@@ -363,4 +363,63 @@ describe('RestQuery.each', () => {
     expect(classSpy.calls.count()).toBe(4);
     expect(results.length).toBe(7);
   });
+
+  it('should work with query on relations', async () => {
+    const objectA = new Parse.Object('Letter', { value: 'A' });
+    const objectB = new Parse.Object('Letter', { value: 'B' });
+
+    const object1 = new Parse.Object('Number', { value: '1' });
+    const object2 = new Parse.Object('Number', { value: '2' });
+    const object3 = new Parse.Object('Number', { value: '3' });
+    const object4 = new Parse.Object('Number', { value: '4' });
+    await Parse.Object.saveAll([object1, object2, object3, object4]);
+
+    objectA.relation('numbers').add(object1);
+    objectB.relation('numbers').add(object2);
+    await Parse.Object.saveAll([objectA, objectB]);
+
+    const config = Config.get('test');
+
+    /* Two query needed since objectId are sorted and we can't know wich one
+     ** going to be the first and then skip by the $gt added by each */
+    const queryOne = new RestQuery(
+      config,
+      auth.master(config),
+      'Letter',
+      {
+        numbers: {
+          __type: 'Pointer',
+          className: 'Number',
+          objectId: object1.id,
+        },
+      },
+      { limit: 1 }
+    );
+    const queryTwo = new RestQuery(
+      config,
+      auth.master(config),
+      'Letter',
+      {
+        numbers: {
+          __type: 'Pointer',
+          className: 'Number',
+          objectId: object2.id,
+        },
+      },
+      { limit: 1 }
+    );
+
+    const classSpy = spyOn(RestQuery.prototype, 'execute').and.callThrough();
+    const resultsOne = [];
+    const resultsTwo = [];
+    await queryOne.each(result => {
+      resultsOne.push(result);
+    });
+    await queryTwo.each(result => {
+      resultsTwo.push(result);
+    });
+    expect(classSpy.calls.count()).toBe(4);
+    expect(resultsOne.length).toBe(1);
+    expect(resultsTwo.length).toBe(1);
+  });
 });

src/RestQuery.js

@@ -223,7 +223,9 @@ RestQuery.prototype.each = function(callback) {
       results.forEach(callback);
       finished = results.length < restOptions.limit;
       if (!finished) {
-        restWhere.objectId = { $gt: results[results.length - 1].objectId };
+        restWhere.objectId = Object.assign({}, restWhere.objectId, {
+          $gt: results[results.length - 1].objectId,
+        });
       }
     }
   );