From b7a2bf45d0af3b072637f395c003857be020667f Mon Sep 17 00:00:00 2001
From: Josh Beam <josh.beam@workiva.com>
Date: Thu, 30 Mar 2017 13:30:01 -0400
Subject: [PATCH] Don't call setState when AbstractTransitionComponent is
 unmounting.

This resolves a warning of the form "Warning: setState(...): Can only update a mounted or mounting component. This usually means you called setState() on an unmounted component. This is a no-op."
---
 lib/src/component/abstract_transition.dart    | 10 +++++++++-
 .../component/abstract_transition_test.dart   | 20 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/lib/src/component/abstract_transition.dart b/lib/src/component/abstract_transition.dart
index 540195afd..dc4c7a9b5 100644
--- a/lib/src/component/abstract_transition.dart
+++ b/lib/src/component/abstract_transition.dart
@@ -281,8 +281,16 @@ abstract class AbstractTransitionComponent<T extends AbstractTransitionProps, S
     }
   }
 
+  var _isMounted = false;
+
+  @override
+  void componentDidMount() {
+    _isMounted = true;
+  }
+
   @override
   void componentWillUnmount() {
+    _isMounted = false;
     _cancelTransitionEventListener();
   }
 
@@ -333,7 +341,7 @@ abstract class AbstractTransitionComponent<T extends AbstractTransitionProps, S
       });
     } else {
       onNextTransitionEnd(() {
-        if (state.transitionPhase == TransitionPhase.HIDING) {
+        if (_isMounted && state.transitionPhase == TransitionPhase.HIDING) {
           setState(newState()
             ..transitionPhase = TransitionPhase.HIDDEN
           );
diff --git a/test/over_react/component/abstract_transition_test.dart b/test/over_react/component/abstract_transition_test.dart
index 1ebf87522..ff1ef9a5f 100644
--- a/test/over_react/component/abstract_transition_test.dart
+++ b/test/over_react/component/abstract_transition_test.dart
@@ -440,6 +440,18 @@ main() {
 
       stopRecordingValidationWarnings();
     });
+
+    test('does not set hidden state when not mounted', () async {
+      var renderedInstance = render(Transitioner());
+      TransitionerComponent transitioner = getDartComponent(renderedInstance);
+      transitioner.setState(transitioner.newState()..transitionPhase = TransitionPhase.HIDING);
+
+      transitioner.handleHiding();
+      transitioner.componentWillUnmount();
+      await triggerTransitionEnd(transitioner.getTransitionDomNode());
+
+      expect(transitioner.transitionPhasesSet, orderedEquals([TransitionPhase.HIDING]));
+    });
   });
 }
 
@@ -552,4 +564,12 @@ class TransitionerComponent extends AbstractTransitionComponent<TransitionerProp
       props.onHandleHidden();
     }
   }
+
+  List<TransitionPhase> transitionPhasesSet = [];
+
+  @override
+  void setState(dynamic newState, [callback()]) {
+    super.setState(newState, callback);
+    transitionPhasesSet.add(newState.transitionPhase);
+  }
 }