Fix StreamQueue.withTransaction(). (#24)

CHANGELOG.md

@@ -6,6 +6,9 @@
 * Fix a bug where rejecting a `StreamQueueTransaction` would throw a
   `StateError` if `StreamQueue.rest` had been called on one of its child queues.
 
+* `StreamQueue.withTransaction()` now properly returns whether or not the
+  transaction was committed.
+
 ## 1.12.0
 
 * Add an `AsyncCache` class that caches asynchronous operations for a period of

lib/src/stream_queue.dart

@@ -328,6 +328,7 @@ abstract class StreamQueue<T> {
       } else {
         transaction.reject();
       }
+      return result;
     }, onError: (error) {
       transaction.commit(queue);
       throw error;

test/stream_queue_test.dart

@@ -1004,6 +1004,11 @@ main() {
 
       expect(events.next, completion(3));
     });
+
+    test("returns whether the transaction succeeded", () {
+      expect(events.withTransaction((_) async => true), completion(isTrue));
+      expect(events.withTransaction((_) async => false), completion(isFalse));
+    });
   });
 
   group("cancelable operation", () {