Use a preventative solution with a proper test

Workiva · Mar 4, 2024 · 242cf97 · 242cf97
1 parent 90aea8c
commit 242cf97
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Showing 2 changed files with 31 additions and 9 deletions.
diff --git a/lib/src/lifecycle_module.dart b/lib/src/lifecycle_module.dart
@@ -507,6 +507,14 @@ abstract class LifecycleModule extends SimpleModule with Disposable {
 
     final completer = Completer<Null>();
     onWillLoadChildModule(childModule).then((_) async {
+      // It is possible to reach this point due to the asynchrony of onWillLoadChildModule.
+      // In that case, simply do not load the child module and instead dispose it.
+      if (isUnloaded || isUnloading) {
+        await childModule.dispose();
+        completer.complete();
+        return;
+      }
+
       _willLoadChildModuleController.add(childModule);
 
       final childModuleWillUnloadSub = listenToStream(
@@ -879,15 +887,6 @@ abstract class LifecycleModule extends SimpleModule with Disposable {
   @override
   @protected
   Future<Null> onWillDispose() async {
-    // It is possible for child modules to be added to the list of children after unload
-    // but before dispose due to asynchrony. Continuing with dispose will cause these to
-    // be disposed which will trigger unload and cause exceptions due to the parent being
-    // partialy disposed. Ensure we give everything a chance to be unloaded before proceeding.
-    await Future.wait(_childModules
-        .toList()
-        .where((child) => !child.isUnloaded)
-        .map((child) => child.unload()));
-
     if (isInstantiated || isUnloaded) {
       return;
     }

diff --git a/test/lifecycle_module_test.dart b/test/lifecycle_module_test.dart
@@ -1756,6 +1756,29 @@ void runTests(bool runSpanTests) {
             childModule.eventList, equals(['willLoad', 'onLoad', 'didLoad']));
       });
 
+      test('followed by parent unload causes child to dispose and never load',
+          () async {
+        parentModule.eventList?.clear();
+        final load = parentModule.loadChildModule(childModule);
+
+        await parentModule.unload();
+        await load;
+
+        expect(
+          parentModule.eventList,
+          equals([
+            'onWillLoadChildModule',
+            'onShouldUnload',
+            'willUnload',
+            'onUnload',
+            'didUnload',
+            'onDispose'
+          ]),
+        );
+
+        expect(childModule.eventList, equals(['onDispose']));
+      });
+
       test('should emit lifecycle log events', () async {
         expect(
             Logger.root.onRecord,