From 6722e3d5166d84acffd80dc7173300681f1912d5 Mon Sep 17 00:00:00 2001
From: Adam Barth <abarth@chromium.org>
Date: Sat, 20 Feb 2016 22:06:00 -0800
Subject: [PATCH] Animation status callbacks should be re-entrant

We should mutate the status of the AnimationController before calling
the status callbacks so that we're prepared to be re-entered.

Fixes #1911
---
 .../src/animation/animation_controller.dart   |  9 +++--
 .../animation/animation_controller_test.dart  | 40 +++++++++++++++++++
 2 files changed, 45 insertions(+), 4 deletions(-)
 create mode 100644 packages/flutter/test/animation/animation_controller_test.dart

diff --git a/packages/flutter/lib/src/animation/animation_controller.dart b/packages/flutter/lib/src/animation/animation_controller.dart
index 124aa31285..b6846a9aa6 100644
--- a/packages/flutter/lib/src/animation/animation_controller.dart
+++ b/packages/flutter/lib/src/animation/animation_controller.dart
@@ -163,10 +163,11 @@ class AnimationController extends Animation<double>
 
   AnimationStatus _lastStatus = AnimationStatus.dismissed;
   void _checkStatusChanged() {
-    AnimationStatus currentStatus = status;
-    if (currentStatus != _lastStatus)
-      notifyStatusListeners(status);
-    _lastStatus = currentStatus;
+    AnimationStatus newStatus = status;
+    AnimationStatus oldStatus = _lastStatus;
+    _lastStatus = newStatus;
+    if (oldStatus != newStatus)
+      notifyStatusListeners(newStatus);
   }
 
   /// Drives the animation from its current value to target.
diff --git a/packages/flutter/test/animation/animation_controller_test.dart b/packages/flutter/test/animation/animation_controller_test.dart
new file mode 100644
index 0000000000..cb283f5612
--- /dev/null
+++ b/packages/flutter/test/animation/animation_controller_test.dart
@@ -0,0 +1,40 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/animation.dart';
+import 'package:flutter/scheduler.dart';
+import 'package:flutter/widgets.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test("Can set value during status callback", () {
+    WidgetFlutterBinding.ensureInitialized();
+    AnimationController controller = new AnimationController(
+      duration: const Duration(milliseconds: 100)
+    );
+    bool didComplete = false;
+    bool didDismiss = false;
+    controller.addStatusListener((AnimationStatus status) {
+      if (status == AnimationStatus.completed) {
+        didComplete = true;
+        controller.value = 0.0;
+        controller.forward();
+      } else if (status == AnimationStatus.dismissed) {
+        didDismiss = true;
+        controller.value = 0.0;
+        controller.forward();
+      }
+    });
+
+    controller.forward();
+    expect(didComplete, isFalse);
+    expect(didDismiss, isFalse);
+    Scheduler.instance.handleBeginFrame(const Duration(seconds: 1));
+    expect(didComplete, isFalse);
+    expect(didDismiss, isFalse);
+    Scheduler.instance.handleBeginFrame(const Duration(seconds: 2));
+    expect(didComplete, isTrue);
+    expect(didDismiss, isTrue);
+  });
+}