Merge pull request #2872 from abarth/fix_inherited

Inherited widgets should work across reactivations

packages/flutter/lib/src/widgets/framework.dart

@@ -911,10 +911,9 @@ abstract class Element implements BuildContext {
 
   void activate(Element parent, dynamic newSlot) {
     assert(_debugLifecycleState == _ElementLifecycle.inactive);
-    _reactivate();
     _parent = parent;
+    _reactivate();
     _updateDepth();
-    _updateInheritance();
     attachRenderObject(newSlot);
     assert(_debugLifecycleState == _ElementLifecycle.active);
   }
@@ -925,6 +924,7 @@ abstract class Element implements BuildContext {
     assert(depth != null);
     assert(!_active);
     _active = true;
+    _updateInheritance();
     assert(() { _debugLifecycleState = _ElementLifecycle.active; return true; });
     visitChildren((Element child) => child._reactivate());
   }
@@ -939,6 +939,7 @@ abstract class Element implements BuildContext {
         dependency._dependents.remove(this);
       _dependencies.clear();
     }
+    _inheritedWidgets = null;
     _active = false;
     assert(() { _debugLifecycleState = _ElementLifecycle.inactive; return true; });
   }
@@ -981,6 +982,7 @@ abstract class Element implements BuildContext {
   }
 
   void _updateInheritance() {
+    assert(_active);
     _inheritedWidgets = _parent?._inheritedWidgets;
   }
 
@@ -1545,6 +1547,7 @@ class InheritedElement extends _ProxyElement {
 
   @override
   void _updateInheritance() {
+    assert(_active);
     final Map<Type, InheritedElement> incomingWidgets = _parent?._inheritedWidgets;
     if (incomingWidgets != null)
       _inheritedWidgets = new Map<Type, InheritedElement>.from(incomingWidgets);

packages/flutter/test/widget/inherited_test.dart

+// Copyright 2015 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_test/flutter_test.dart';
+import 'package:flutter/material.dart';
+import 'package:test/test.dart';
+
+class TestInherited extends InheritedWidget {
+  TestInherited({ Key key, Widget child, this.shouldNotify: true })
+    : super(key: key, child: child);
+
+  final bool shouldNotify;
+
+  @override
+  bool updateShouldNotify(InheritedWidget oldWidget) {
+    return shouldNotify;
+  }
+}
+
+void main() {
+  test('Inherited notifies dependents', () {
+    testWidgets((WidgetTester tester) {
+      List<TestInherited> log = <TestInherited>[];
+
+      Builder builder = new Builder(
+        builder: (BuildContext context) {
+          log.add(context.inheritFromWidgetOfExactType(TestInherited));
+          return new Container();
+        }
+      );
+
+      TestInherited first = new TestInherited(child: builder);
+      tester.pumpWidget(first);
+
+      expect(log, equals([first]));
+
+      TestInherited second = new TestInherited(child: builder, shouldNotify: false);
+      tester.pumpWidget(second);
+
+      expect(log, equals([first]));
+
+      TestInherited third = new TestInherited(child: builder, shouldNotify: true);
+      tester.pumpWidget(third);
+
+      expect(log, equals([first, third]));
+    });
+  });
+
+  test('Update inherited when reparenting state', () {
+    testWidgets((WidgetTester tester) {
+      GlobalKey globalKey = new GlobalKey();
+      List<TestInherited> log = <TestInherited>[];
+
+      TestInherited build() {
+        return new TestInherited(
+          key: new UniqueKey(),
+          child: new Container(
+            key: globalKey,
+            child: new Builder(
+              builder: (BuildContext context) {
+                log.add(context.inheritFromWidgetOfExactType(TestInherited));
+                return new Container();
+              }
+            )
+          )
+        );
+      }
+
+      TestInherited first = build();
+      tester.pumpWidget(first);
+
+      expect(log, equals([first]));
+
+      TestInherited second = build();
+      tester.pumpWidget(second);
+
+      expect(log, equals([first, second]));
+    });
+  });
+}