Merge pull request #4 from mixcloud/gd-mutation-errors

Reject mutation onFailure with the error message

src/__tests__/testMutate.js

@@ -59,7 +59,9 @@ describe('mutate', () => {
     it('should return a promise and handle onFailure', () => {
         return new Promise(resolve => {
             mutate({}, {}).then(null, resolve);
-            Relay.mutations[0].args[4].onFailure();
+            Relay.mutations[0].args[4].onFailure({getError: () => "Error message"});
+        }).then((error) => {
+            expect(error).toBe("Error message");
         });
     });
 });

src/mutate.js

@@ -55,7 +55,7 @@ export default function mutate(env: Relay.Environment, config: MutationConfig):
     return new Promise((resolve, reject) => {
         const mutation = new Relay.GraphQLMutation(query, variables, files, env, {
             onSuccess: resolve,
-            onFailure: reject
+            onFailure: (transaction) => reject(transaction.getError())
         });
         if (optimisticResponse) {
             mutation.applyOptimistic(query, optimisticResponse, configs);