Don't error when attempting to sort on an object field (#4806)

* add failing test to demonstrate that you can't sort on a
field in an object.

* Only validate the base of the field name.

* fix test name

* Only test sort for mongo.

* pg order by nested object

* level 2 test

* Factor out operation to get a field's base name.  Add comment.

* tweak comment wording so it wont make my grammar teacher angry.

spec/ParseQuery.spec.js

@@ -1538,6 +1538,90 @@ describe('Parse.Query testing', () => {
     });
   });
 
+  it('can order on an object string field', function (done) {
+    const testSet = [
+      { sortField: { value: "Z" } },
+      { sortField: { value: "A" } },
+      { sortField: { value: "M" } },
+    ];
+
+    const objects = testSet.map(e => new Parse.Object('Test', e));
+    Parse.Object.saveAll(objects)
+      .then(() => new Parse.Query('Test').addDescending('sortField.value').first())
+      .then((result) => {
+        expect(result.get('sortField').value).toBe("Z");
+        return new Parse.Query('Test').addAscending('sortField.value').first()
+      })
+      .then((result) => {
+        expect(result.get('sortField').value).toBe("A");
+        done();
+      })
+      .catch(done.fail);
+  });
+
+  it('can order on an object string field (level 2)', function (done) {
+    const testSet = [
+      { sortField: { value: { field: "Z" } } },
+      { sortField: { value: { field: "A" } } },
+      { sortField: { value: { field: "M" } } },
+    ];
+
+    const objects = testSet.map(e => new Parse.Object('Test', e));
+    Parse.Object.saveAll(objects)
+      .then(() => new Parse.Query('Test').addDescending('sortField.value.field').first())
+      .then((result) => {
+        expect(result.get('sortField').value.field).toBe("Z");
+        return new Parse.Query('Test').addAscending('sortField.value.field').first()
+      })
+      .then((result) => {
+        expect(result.get('sortField').value.field).toBe("A");
+        done();
+      })
+      .catch(done.fail);
+  });
+
+  it('can order on an object number field', function (done) {
+    const testSet = [
+      { sortField: { value: 10 } },
+      { sortField: { value: 1 } },
+      { sortField: { value: 5 } },
+    ];
+
+    const objects = testSet.map(e => new Parse.Object('Test', e));
+    Parse.Object.saveAll(objects)
+      .then(() => new Parse.Query('Test').addDescending('sortField.value').first())
+      .then((result) => {
+        expect(result.get('sortField').value).toBe(10);
+        return new Parse.Query('Test').addAscending('sortField.value').first()
+      })
+      .then((result) => {
+        expect(result.get('sortField').value).toBe(1);
+        done();
+      })
+      .catch(done.fail);
+  });
+
+  it('can order on an object number field (level 2)', function (done) {
+    const testSet = [
+      { sortField: { value: { field: 10 } } },
+      { sortField: { value: { field: 1 } } },
+      { sortField: { value: { field: 5 } } },
+    ];
+
+    const objects = testSet.map(e => new Parse.Object('Test', e));
+    Parse.Object.saveAll(objects)
+      .then(() => new Parse.Query('Test').addDescending('sortField.value.field').first())
+      .then((result) => {
+        expect(result.get('sortField').value.field).toBe(10);
+        return new Parse.Query('Test').addAscending('sortField.value.field').first()
+      })
+      .then((result) => {
+        expect(result.get('sortField').value.field).toBe(1);
+        done();
+      })
+      .catch(done.fail);
+  });
+
   it("order by ascending number then descending string", function(done) {
     const strings = ["a", "b", "c", "d"];
     const makeBoxedNumber = function(num, i) {