Don't perform cannAddField check if using master key

spec/DatabaseController.spec.js

@@ -14,4 +14,47 @@ describe('DatabaseController', () => {
       fail();
     });
   });
+
+  describe('canAddField is called appropriately', () => {
+    let adapter = new MongoStorageAdapter('mongodb://localhost:27017/test');
+    let databaseController = new DatabaseController(adapter, {
+		collectionPrefix: 'test_'
+    });
+
+    var connectionP = databaseController.connect()
+
+    it("is ignored if using master key", done => {
+      connectionP.then(() => {
+        databaseController.canAddField = function() {
+          console.log('error: canAddField was called');
+          fail();
+        }
+
+        // master key is implied, by not passing in an acl
+        var object = {};
+        var query = {};
+        var acl = {/* no acl field */}
+        return databaseController.validateObject('SomeObj', object, query, acl).then(done);
+      }).catch(error => {
+        console.log('error', error.stack);
+        fail();
+      });
+    });
+
+    it("is called with an explicit ACL, canAddField is called", done => {
+      connectionP.then(() => {
+        databaseController.canAddField = function() {
+          done();
+        }
+
+        var object = {};
+        var query = {};
+        var acl = {acl: [] /* explicit empty ACL */}
+        return databaseController.validateObject('SomeObj', object, query, acl);
+      }).catch(error => {
+        console.log('error', error.stack);
+        fail();
+      });
+    });
+  });
 });

src/Controllers/DatabaseController.js

@@ -102,10 +102,15 @@ DatabaseController.prototype.redirectClassNameForKey = function(className, key)
 // This does not update this.schema, because in a situation like a
 // batch request, that could confuse other users of the schema.
 DatabaseController.prototype.validateObject = function(className, object, query, options) {
+  var isMaster = !('acl' in options);
   let schema;
   return this.loadSchema().then(s => {
     schema = s;
-    return this.canAddField(schema, className, object, options.acl || []);
+
+    // If we are using the master key, we can always add fields
+    if (!isMaster) {
+      return this.canAddField(schema, className, object, options.acl || []);
+    }
   }).then(() => {
     return schema.validateObject(className, object, query);
   });