Fix problems with _keys in nested objects

spec/ParseObject.spec.js

@@ -1736,4 +1736,33 @@ describe('Parse.Object testing', () => {
     });
   });
 
+
+  it("should create nested keys with _", done => {
+    const object = new Parse.Object("AnObject");
+    object.set("foo", {
+      "_bar": "_",
+      "baz_bar": 1,
+      "__foo_bar": true,
+      "_0": "underscore_zero",
+      "_more": {
+        "_nested": "key"
+      }
+    });
+    object.save().then( res => {
+      ok(res);
+      return res.fetch();
+    }).then( res => {
+      const foo = res.get("foo");
+      expect(foo["_bar"]).toEqual("_");
+      expect(foo["baz_bar"]).toEqual(1);
+      expect(foo["__foo_bar"]).toBe(true);
+      expect(foo["_0"]).toEqual("underscore_zero");
+      expect(foo["_more"]["_nested"]).toEqual("key");
+      done();
+    }).fail( err => {
+      console.error(err);
+      fail("should not fail");
+      done();
+    })
+  })
 });

src/transform.js

@@ -586,7 +586,7 @@ function transformUpdateOperator(operator, flatten) {
 
 // Converts from a mongo-format object to a REST-format object.
 // Does not strip out anything based on a lack of authentication.
-function untransformObject(schema, className, mongoObject) {
+function untransformObject(schema, className, mongoObject, isNestedObject = false) {
   switch(typeof mongoObject) {
   case 'string':
   case 'number':
@@ -683,10 +683,8 @@ function untransformObject(schema, className, mongoObject) {
             objectId: objData[1]
           };
           break;
-        } else if (key[0] == '_' && key != '__type') {
+        } else if (!isNestedObject && key[0] == '_' && key != '__type') {
           throw ('bad key in untransform: ' + key);
-        //} else if (mongoObject[key] === null) {
-          //break;
         } else {
           var expectedType = schema.getExpectedType(className, key);
           var value = mongoObject[key];
@@ -700,7 +698,7 @@ function untransformObject(schema, className, mongoObject) {
           }
         }
         restObject[key] = untransformObject(schema, className,
-                                            mongoObject[key]);
+                                            mongoObject[key], true);
       }
     }
     return restObject;