Remove factory with lazy initialization of current container

src/Forms/Prism.Forms/PrismApplicationBase.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Linq;
 using Prism.AppModel;
 using Prism.Behaviors;
@@ -22,6 +23,8 @@ namespace Prism
     /// </summary>
     public abstract class PrismApplicationBase : Application
     {
+        private static bool _initialized;
+
         /// <summary>
         /// Gets the Current PrismApplication
         /// </summary>
@@ -140,20 +143,31 @@ private INavigationService CreateNavigationService(object view)
         /// </summary>
         protected virtual void Initialize()
         {
-            ContainerLocator.SetContainerExtension(CreateContainerExtension);
-            _containerExtension = ContainerLocator.Current;
-            RegisterRequiredTypes(_containerExtension);
-            PlatformInitializer?.RegisterTypes(_containerExtension);
-            RegisterTypes(_containerExtension);
-            _containerExtension.FinalizeExtension();
+            if(!_initialized)
+            {
+                ContainerLocator.TrySetContainerExtension(CreateContainerExtension());
+                _containerExtension = ContainerLocator.Current;
+                RegisterRequiredTypes(_containerExtension);
+                PlatformInitializer?.RegisterTypes(_containerExtension);
+                RegisterTypes(_containerExtension);
+                _containerExtension.FinalizeExtension();
+
+                _moduleCatalog = Container.Resolve<IModuleCatalog>();
+                ConfigureModuleCatalog(_moduleCatalog);
 
-            _moduleCatalog = Container.Resolve<IModuleCatalog>();
-            ConfigureModuleCatalog(_moduleCatalog);
+                _containerExtension.CreateScope();
+                NavigationService = _containerExtension.Resolve<INavigationService>();
 
-            _containerExtension.CreateScope();
-            NavigationService = _containerExtension.Resolve<INavigationService>();
+                InitializeModules();
+            }
+            else
+            {
+                _containerExtension = ContainerLocator.Current;
+                _containerExtension.CreateScope();
+                NavigationService = _containerExtension.Resolve<INavigationService>();
+            }
 
-            InitializeModules();
+            _initialized = true;
         }
 
         /// <summary>
@@ -259,5 +273,17 @@ private void PrismApplicationBase_ModalPopped(object sender, ModalPoppedEventArg
                 _previousPage = null;
             }
         }
+
+        /// <summary>
+        /// This method is for Unit Testing Purposes only. By default we do not reinitialize the container if the static
+        /// Initialization flag is already set to true. This could be the case on Android where the MainActivity is recreated
+        /// and the Application.Current was nulled out requiring a new instance of the Application to be created. This will preserve
+        /// the Registrations and Singletons that are already initialized in the initial container.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void ResetInitialization()
+        {
+            _initialized = false;
+        }
     }
 }

src/Maui/Prism.Maui/PrismAppBuilder.cs

@@ -76,7 +76,7 @@ internal PrismAppBuilder(IContainerExtension containerExtension, MauiAppBuilder
         });
 
         ContainerLocator.ResetContainer();
-        ContainerLocator.SetContainerExtension(() => containerExtension);
+        ContainerLocator.SetContainerExtension(containerExtension);
 
         containerExtension.RegisterInstance(this);
         containerExtension.RegisterSingleton<IMauiInitializeService, PrismInitializationService>();

src/Prism.Core/Ioc/ContainerLocator.cs

@@ -1,4 +1,5 @@
-using System;
+#nullable enable
+using System;
 using System.ComponentModel;
 
 namespace Prism.Ioc
@@ -9,16 +10,14 @@
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static class ContainerLocator
     {
-        private static Lazy<IContainerExtension> _lazyContainer;
-
-        private static IContainerExtension _current;
+        private static IContainerExtension? _current;
 
         /// <summary>
         /// Gets the current <see cref="IContainerExtension" />.
         /// </summary>
         [EditorBrowsable(EditorBrowsableState.Never)]
         public static IContainerExtension Current =>
-            _current ?? (_current = _lazyContainer?.Value);
+            _current ?? throw new InvalidOperationException("The `ContainerLocator.SetContainerExtension` method has not been invoked");
 
         /// <summary>
         /// Gets the <see cref="IContainerProvider" />
@@ -27,15 +26,34 @@
             Current;
 
         /// <summary>
-        /// Sets the Container Factory to use if the Current <see cref="IContainerProvider" /> is null
+        /// Sets the Container to use if the <see cref="IContainerProvider" /> is null. Otherwise this will throw an exception.
         /// </summary>
-        /// <param name="factory"></param>
+        /// <param name="instance">The current instance to set</param>
         /// <remarks>
-        /// NOTE: We want to use Lazy Initialization in case the container is first created
-        /// prior to Prism initializing which could be the case with Shiny
-        /// </remarks>
-        public static void SetContainerExtension(Func<IContainerExtension> factory) =>
-            _lazyContainer = new Lazy<IContainerExtension>(factory);
+        /// <exception cref="InvalidOperationException">Throws an exception if the Container has already been set.</exception>
+        public static void SetContainerExtension(IContainerExtension instance)
+        {
+            if (_current is not null)
+            {
+                throw new InvalidOperationException("The Container has already been initialized with the ContainerLocator. Please use TrySetContainerExtension or Reset the ContainerLocator prior to invoking the SetContainerExtensionMethod.");
+            }
+            _current = instance;
+        }
+
+        /// <summary>
+        /// Returns <c>True</c> and sets the Container if the <see cref="IContainerProvider"/> is null. Otherwise
+        /// will return <c>False</c>
+        /// </summary>
+        /// <param name="instance">The instance of the <see cref="IContainerExtension"/> to set.</param>
+        /// <returns><c>True</c> if the Container was set.</returns>
+        public static bool TrySetContainerExtension(IContainerExtension instance)
+        {
+            if (_current is not null)
+                return false;
+
+            _current = instance;
+            return true;
+        }
 
         /// <summary>
         /// Used for Testing to Reset the Current Container
@@ -44,7 +62,6 @@
         public static void ResetContainer()
         {
             _current = null;
-            _lazyContainer = null;
         }
     }
 }

src/Uno/Prism.Uno/PrismApplicationBase.cs

@@ -101,7 +101,7 @@ protected virtual void ConfigureServices(IServiceCollection services) { }
         /// </summary>
         protected virtual void Initialize(IApplicationBuilder builder)
         {
-            ContainerLocator.SetContainerExtension(CreateContainerExtension);
+            ContainerLocator.SetContainerExtension(CreateContainerExtension());
             _containerExtension = ContainerLocator.Current;
             ConfigureApp(builder);
             builder.Configure(ConfigureHost)

src/Wpf/Prism.Wpf/PrismApplicationBase.cs

@@ -56,7 +56,7 @@ protected virtual void ConfigureViewModelLocator()
         /// </summary>
         protected virtual void Initialize()
         {
-            ContainerLocator.SetContainerExtension(CreateContainerExtension);
+            ContainerLocator.SetContainerExtension(CreateContainerExtension());
             _containerExtension = ContainerLocator.Current;
             _moduleCatalog = CreateModuleCatalog();
             RegisterRequiredTypes(_containerExtension);

src/Wpf/Prism.Wpf/PrismBootstrapperBase.cs

@@ -53,7 +53,7 @@ protected virtual void ConfigureViewModelLocator()
         /// </summary>
         protected virtual void Initialize()
         {
-            ContainerLocator.SetContainerExtension(CreateContainerExtension);
+            ContainerLocator.SetContainerExtension(CreateContainerExtension());
             _containerExtension = ContainerLocator.Current;
             _moduleCatalog = CreateModuleCatalog();
             RegisterRequiredTypes(_containerExtension);

tests/Containers/Prism.Container.Shared/Tests/ContainerResolutionExceptionFixture.cs

@@ -43,7 +43,7 @@ public void GetErrorsDoesNotThrowException()
         {
             ContainerLocator.ResetContainer();
             var container = Setup.CreateContainer();
-            ContainerLocator.SetContainerExtension(() => Setup.Extension);
+            Assert.False(ContainerLocator.TrySetContainerExtension(Setup.Extension));
             Setup.Registry.Register<object, BadView>("BadView");
 
             var ex = Record.Exception(() => container.Resolve<object>("BadView"));
@@ -60,7 +60,7 @@ public void GetErrorsLocatesIssueWithBadView()
         {
             ContainerLocator.ResetContainer();
             var container = Setup.CreateContainer();
-            ContainerLocator.SetContainerExtension(() => Setup.Extension);
+            Assert.False(ContainerLocator.TrySetContainerExtension(Setup.Extension));
             Setup.Registry.Register<object, BadView>("BadView");
 
             var ex = Record.Exception(() => container.Resolve<object>("BadView"));
@@ -77,7 +77,7 @@ public void GetErrorsLocatesTargetInvocationException()
         {
             ContainerLocator.ResetContainer();
             var container = Setup.CreateContainer();
-            ContainerLocator.SetContainerExtension(() => Setup.Extension);
+            Assert.False(ContainerLocator.TrySetContainerExtension(Setup.Extension));
             Setup.Registry.Register<object, BadView>("BadView");
 
             var ex = Record.Exception(() => container.Resolve<object>("BadView"));
@@ -94,7 +94,7 @@ public void GetErrorsLocatesXamlParseException()
         {
             ContainerLocator.ResetContainer();
             var container = Setup.CreateContainer();
-            ContainerLocator.SetContainerExtension(() => Setup.Extension);
+            Assert.False(ContainerLocator.TrySetContainerExtension(Setup.Extension));
             Setup.Registry.Register<object, BadView>("BadView");
 
             var ex = Record.Exception(() => container.Resolve<object>("BadView"));
@@ -111,7 +111,7 @@ public void LocatesUnregisteredServiceType()
         {
             ContainerLocator.ResetContainer();
             var container = Setup.CreateContainer();
-            ContainerLocator.SetContainerExtension(() => Setup.Extension);
+            Assert.False(ContainerLocator.TrySetContainerExtension(Setup.Extension));
 
             var ex = Record.Exception(() => container.Resolve<ConstructorArgumentViewModel>());
 
@@ -127,7 +127,7 @@ public void LocatesUnregisteredServiceWithMissingRegistration()
         {
             ContainerLocator.ResetContainer();
             var container = Setup.CreateContainer();
-            ContainerLocator.SetContainerExtension(() => Setup.Extension);
+            Assert.False(ContainerLocator.TrySetContainerExtension(Setup.Extension));
 
             var ex = Record.Exception(() => container.Resolve<ConstructorArgumentViewModel>());
 

tests/Containers/Prism.Container.Shared/Tests/ContainerSetup.cs

@@ -20,7 +20,7 @@ public ContainerSetup()
         public IContainerProvider CreateContainer()
         {
             ContainerLocator.ResetContainer();
-            ContainerLocator.SetContainerExtension(() => CreateContainerInternal());
+            ContainerLocator.SetContainerExtension(CreateContainerInternal());
             var container = ContainerLocator.Current;
             container.CreateScope();
             return container;

tests/Forms/Prism.Forms.Regions.Tests/Tests/RegionFixture.cs

@@ -493,7 +493,7 @@ public void NavigateDelegatesToIRegionNavigationService()
                 var containerMock = new Mock<IContainerExtension>();
                 containerMock.Setup(x => x.Resolve(typeof(IRegionNavigationService))).Returns(mockRegionNavigationService.Object);
                 ContainerLocator.ResetContainer();
-                ContainerLocator.SetContainerExtension(() => containerMock.Object);
+                ContainerLocator.SetContainerExtension(containerMock.Object);
 
                 // Act
                 region.NavigationService.RequestNavigate(uri, navigationCallback, navigationParameters);

tests/Forms/Prism.Forms.Regions.Tests/Tests/RegionManagerFixture.cs

@@ -351,7 +351,7 @@ public void CanRegisterViewType()
                 };
                 var containerMock = new Mock<IContainerExtension>();
                 containerMock.Setup(c => c.Resolve(typeof(IRegionViewRegistry))).Returns(mockRegionContentRegistry);
-                ContainerLocator.SetContainerExtension(() => containerMock.Object);
+                ContainerLocator.SetContainerExtension(containerMock.Object);
 
                 var regionManager = new RegionManager();
 
@@ -387,7 +387,7 @@ public void CanRegisterViewTypeGeneric()
                 var containerMock = new Mock<IContainerExtension>();
                 containerMock.Setup(c => c.Resolve(typeof(IRegionViewRegistry))).Returns(mockRegionContentRegistry);
                 ContainerLocator.ResetContainer();
-                ContainerLocator.SetContainerExtension(() => containerMock.Object);
+                ContainerLocator.SetContainerExtension(containerMock.Object);
 
                 var regionManager = new RegionManager();
 

tests/Forms/Prism.Forms.Tests/Navigation/INavigationServiceExtensionsFixture.cs

@@ -21,7 +21,7 @@ public INavigationServiceExtensionsFixture()
             ContainerLocator.ResetContainer();
             var container = new Mock<IContainerExtension>();
             container.Setup(x => x.CreateScope()).Returns(Mock.Of<IScopedProvider>());
-            ContainerLocator.SetContainerExtension(() => container.Object);
+            ContainerLocator.SetContainerExtension(container.Object);
             PageNavigationRegistry.ClearRegistrationCache();
 
             PageNavigationRegistry.Register("NavigationPage", typeof(NavigationPage));

tests/Forms/Prism.Forms.Tests/Navigation/PageNavigationServiceFixture.cs

@@ -26,7 +26,7 @@ public PageNavigationServiceFixture()
 
             ContainerLocator.ResetContainer();
             _container = new PageNavigationContainerMock();
-            ContainerLocator.SetContainerExtension(() => _container);
+            ContainerLocator.SetContainerExtension(_container);
 
             _container.Register("PageMock", typeof(PageMock));
 

tests/Prism.Core.Tests/Ioc/ContainerLocatorFixture.cs

@@ -1,4 +1,5 @@
-using Moq;
+using System;
+using Moq;
 using Prism.Ioc;
 using Xunit;
 
@@ -18,33 +19,51 @@ public class ContainerLocatorFixture
         public void FactoryCreatesContainerExtension()
         {
             Prism.Ioc.ContainerLocator.ResetContainer();
-            Assert.Null(Prism.Ioc.ContainerLocator.Current);
-            Prism.Ioc.ContainerLocator.SetContainerExtension(() => new Mock<IContainerExtension>().Object);
+            Assert.Throws<InvalidOperationException>(() => Prism.Ioc.ContainerLocator.Current);
+            Prism.Ioc.ContainerLocator.SetContainerExtension(new Mock<IContainerExtension>().Object);
             Assert.NotNull(Prism.Ioc.ContainerLocator.Current);
         }
 
         [Fact]
         public void ResetNullsCurrentContainer()
         {
             Prism.Ioc.ContainerLocator.ResetContainer();
-            Assert.Null(Prism.Ioc.ContainerLocator.Current);
-            Prism.Ioc.ContainerLocator.SetContainerExtension(() => new Mock<IContainerExtension>().Object);
+            Assert.Throws<InvalidOperationException>(() => Prism.Ioc.ContainerLocator.Current);
+            Prism.Ioc.ContainerLocator.SetContainerExtension(new Mock<IContainerExtension>().Object);
             Assert.NotNull(Prism.Ioc.ContainerLocator.Current);
             Prism.Ioc.ContainerLocator.ResetContainer();
-            Assert.Null(Prism.Ioc.ContainerLocator.Current);
+            Assert.Throws<InvalidOperationException>(() => Prism.Ioc.ContainerLocator.Current);
         }
 
         [Fact]
-        public void FactoryOnlySetsContainerOnce()
+        public void SetThrowExceptionWhenAlreadyInitialized()
         {
             Prism.Ioc.ContainerLocator.ResetContainer();
             var container = new Mock<IContainerExtension>().Object;
             var container2 = new Mock<IContainerExtension>().Object;
 
-            Prism.Ioc.ContainerLocator.SetContainerExtension(() => container);
+            Prism.Ioc.ContainerLocator.SetContainerExtension(container);
             Assert.Same(container, Prism.Ioc.ContainerLocator.Container);
 
-            Prism.Ioc.ContainerLocator.SetContainerExtension(() => container2);
+            var ex = Record.Exception(() => Prism.Ioc.ContainerLocator.SetContainerExtension(container2));
+            Assert.NotNull(ex);
+            Assert.IsType<InvalidOperationException>(ex);
+            Assert.Same(container, Prism.Ioc.ContainerLocator.Container);
+        }
+
+        [Fact]
+        public void TrySetReturnsFalseWhenSetting2ndContainer()
+        {
+            Prism.Ioc.ContainerLocator.ResetContainer();
+            var container = new Mock<IContainerExtension>().Object;
+            var container2 = new Mock<IContainerExtension>().Object;
+
+            var result = Prism.Ioc.ContainerLocator.TrySetContainerExtension(container);
+            Assert.Same(container, Prism.Ioc.ContainerLocator.Container);
+            Assert.True(result);
+
+            result = Prism.Ioc.ContainerLocator.TrySetContainerExtension(container2);
+            Assert.False(result);
             Assert.NotSame(container2, Prism.Ioc.ContainerLocator.Container);
             Assert.Same(container, Prism.Ioc.ContainerLocator.Container);
         }

tests/Wpf/Prism.Container.Wpf.Shared/Fixtures/Bootstrapper/BootstrapperRunMethodFixture.cs

@@ -1,3 +1,4 @@
+using System;
 using Moq;
 using Prism.Container.Wpf.Mocks;
 using Prism.Events;
@@ -154,7 +155,7 @@ public void RunShouldCallRegisterTypes()
         public void SetsContainerLocatorCurrentContainer()
         {
             ContainerLocator.ResetContainer();
-            Assert.Null(ContainerLocator.Container);
+            Assert.Throws<InvalidOperationException>(() => ContainerLocator.Container);
             var bootstrapper = new MockBootstrapper();
 
             bootstrapper.Run();

tests/Wpf/Prism.Container.Wpf.Shared/Fixtures/Ioc/ContainerProviderExtensionFixture.cs

@@ -42,7 +42,7 @@ static ContainerProviderExtensionFixture()
         public ContainerProviderExtensionFixture()
         {
             ContainerLocator.ResetContainer();
-            ContainerLocator.SetContainerExtension(() => _containerExtension);
+            ContainerLocator.SetContainerExtension(_containerExtension);
         }
 
         public void Dispose()

tests/Wpf/Prism.Container.Wpf.Shared/Fixtures/Regions/RegionNavigationContentLoaderFixture.cs

@@ -20,7 +20,7 @@ public RegionNavigationContentLoaderFixture()
             _container.Register(typeof(IRegionNavigationContentLoader), typeof(RegionNavigationContentLoader));
             _container.Register<IRegionNavigationJournal, RegionNavigationJournal>();
             ContainerLocator.ResetContainer();
-            ContainerLocator.SetContainerExtension(() => _container);
+            ContainerLocator.SetContainerExtension(_container);
         }
 
         [StaFact]