Dispose modules during onLoad if parent is unloaded/unloading

CHANGELOG.md

@@ -1,3 +1,10 @@
+## [3.0.6](https://github.com/Workiva/w_module/compare/3.0.5...3.0.6)
+
+_March 4, 2024_
+
+- **Bug Fix:** A child module which loads during the unload of the parent
+  may cause BadState exceptions.
+
 ## [3.0.0](https://github.com/Workiva/w_module/compare/2.0.5...3.0.0)
 
 _August 18, 2023_

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(

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,