Do not attempt to load satellite assemblies until after MainAsync has executed (#21476)

WASM runtime does not like it when you attempt to load satellite assemblies
for two sets of non-neutral cultures - the first is always loaded. This change
defers loading satellite assemblies until after Program.Main has executed
and the developer has configured the culture for the application.

Fixes #21433

Author: pranavkm

src/Components/WebAssembly/WebAssembly/src/Hosting/EntrypointInvoker.cs

@@ -15,19 +15,10 @@ internal static class EntrypointInvoker
         // In the future we may want Blazor.start to return something that exposes the possibly-async
         // entrypoint result to the JS caller. There's no requirement to do that today, and if we
         // do change this it will be non-breaking.
-        public static void InvokeEntrypoint(string assemblyName, string[] args)
-            => InvokeEntrypoint(assemblyName, args, SatelliteResourcesLoader.Init());
-
-        internal static async void InvokeEntrypoint(string assemblyName, string[] args, SatelliteResourcesLoader satelliteResourcesLoader)
+        public static async void InvokeEntrypoint(string assemblyName, string[] args)
         {
             try
             {
-                // Emscripten sets up the culture for the application based on the user's language preferences.
-                // Before we execute the app's entry point, load satellite assemblies for this culture.
-                // We'll allow users to configure their app culture as part of MainAsync. Loading satellite assemblies
-                // for the configured culture will happen as part of WebAssemblyHost.RunAsync.
-                await satelliteResourcesLoader.LoadCurrentCultureResourcesAsync();
-
                 var assembly = Assembly.Load(assemblyName);
                 var entrypoint = FindUnderlyingEntrypoint(assembly);
                 var @params = entrypoint.GetParameters().Length == 1 ? new object[] { args ?? Array.Empty<string>() } : new object[] { };

src/Components/WebAssembly/WebAssembly/src/Hosting/SatelliteResourcesLoader.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Globalization;
 using System.Reflection;
 using System.Threading.Tasks;
@@ -16,36 +15,14 @@ internal class SatelliteResourcesLoader
         internal const string ReadSatelliteAssemblies = "window.Blazor._internal.readSatelliteAssemblies";
 
         private readonly WebAssemblyJSRuntimeInvoker _invoker;
-        private CultureInfo _previousCulture;
 
         // For unit testing.
         internal SatelliteResourcesLoader(WebAssemblyJSRuntimeInvoker invoker)
         {
             _invoker = invoker;
         }
 
-        public static SatelliteResourcesLoader Instance { get; private set; }
-
-        public static SatelliteResourcesLoader Init()
-        {
-            Debug.Assert(Instance is null, "Init should not be called multiple times.");
-
-            Instance = new SatelliteResourcesLoader(WebAssemblyJSRuntimeInvoker.Instance);
-            return Instance;
-        }
-
-        public ValueTask LoadCurrentCultureResourcesAsync()
-        {
-            if (_previousCulture != CultureInfo.CurrentCulture)
-            {
-                _previousCulture = CultureInfo.CurrentCulture;
-                return LoadSatelliteAssembliesForCurrentCultureAsync();
-            }
-
-            return default;
-        }
-
-        protected virtual async ValueTask LoadSatelliteAssembliesForCurrentCultureAsync()
+        public virtual async ValueTask LoadCurrentCultureResourcesAsync()
         {
             var culturesToLoad = GetCultures(CultureInfo.CurrentCulture);
 

src/Components/WebAssembly/WebAssembly/src/Hosting/WebAssemblyHost.cs

@@ -6,6 +6,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Components.WebAssembly.Infrastructure;
 using Microsoft.AspNetCore.Components.WebAssembly.Rendering;
+using Microsoft.AspNetCore.Components.WebAssembly.Services;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
@@ -58,7 +59,7 @@ internal WebAssemblyHost(IServiceProvider services, IServiceScope scope, IConfig
         /// </summary>
         public IServiceProvider Services => _scope.ServiceProvider;
 
-        internal SatelliteResourcesLoader SatelliteResourcesLoader { get; set; } = SatelliteResourcesLoader.Instance;
+        internal SatelliteResourcesLoader SatelliteResourcesLoader { get; set; } = new SatelliteResourcesLoader(WebAssemblyJSRuntimeInvoker.Instance);
 
         /// <summary>
         /// Disposes the host asynchronously.

src/Components/WebAssembly/WebAssembly/test/Hosting/EntrypointInvokerTest.cs

@@ -2,15 +2,12 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Globalization;
 using System.IO;
 using System.Reflection;
 using System.Runtime.Loader;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Components.WebAssembly.Services;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
-using Moq;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Components.WebAssembly.Hosting
@@ -36,7 +33,7 @@ public void InvokesEntrypoint_Sync_Success(bool hasReturnValue, bool hasParams)
 }", out var didMainExecute);
 
             // Act
-            EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { }, new TestSatelliteResourcesLoader());
+            EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { });
 
             // Assert
             Assert.True(didMainExecute());
@@ -66,7 +63,7 @@ public void InvokesEntrypoint_Async_Success(bool hasReturnValue, bool hasParams)
             // Act/Assert 1: Waits for task
             // The fact that we're not blocking here proves that we're not executing the
             // metadata-declared entrypoint, as that would block
-            EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { }, new TestSatelliteResourcesLoader());
+            EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { });
             Assert.False(didMainExecute());
 
             // Act/Assert 2: Continues
@@ -91,7 +88,7 @@ public static void Main()
             // to handle the exception. We can't assert about what it does here, because that
             // would involve capturing console output, which isn't safe in unit tests. Instead
             // we'll check this in E2E tests.
-            EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { }, new TestSatelliteResourcesLoader());
+            EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { });
             Assert.True(didMainExecute());
         }
 
@@ -110,7 +107,7 @@ public static async Task Main()
 }", out var didMainExecute);
 
             // Act/Assert 1: Waits for task
-            EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { }, new TestSatelliteResourcesLoader());
+            EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { });
             Assert.False(didMainExecute());
 
             // Act/Assert 2: Continues
@@ -152,15 +149,5 @@ public static class Program
 
             return assembly;
         }
-
-        private class TestSatelliteResourcesLoader : SatelliteResourcesLoader
-        {
-            internal TestSatelliteResourcesLoader()
-                : base(WebAssemblyJSRuntimeInvoker.Instance)
-            {
-            }
-
-            protected override ValueTask LoadSatelliteAssembliesForCurrentCultureAsync() => default;
-        }
     }
 }

src/Components/WebAssembly/WebAssembly/test/Hosting/SatelliteResourcesLoaderTest.cs

@@ -70,45 +70,5 @@ public async Task LoadCurrentCultureResourcesAsync_DoesNotReadAssembliesWhenTher
             // Assert
             invoker.Verify(i => i.InvokeUnmarshalled<object, object, object, object[]>(ReadSatelliteAssemblies, null, null, null), Times.Never());
         }
-
-        [Fact]
-        public async Task LoadCurrentCultureResourcesAsync_AttemptsToReadAssemblies_IfCultureIsChangedBetweenInvocation()
-        {
-            // Arrange
-            using var cultureReplacer = new CultureReplacer("en-GB");
-            var invoker = new Mock<WebAssemblyJSRuntimeInvoker>();
-            invoker.Setup(i => i.InvokeUnmarshalled<string[], object, object, Task<object>>(GetSatelliteAssemblies, It.IsAny<string[]>(), null, null))
-                 .Returns(Task.FromResult<object>(0))
-                 .Verifiable();
-
-            var loader = new SatelliteResourcesLoader(invoker.Object);
-
-            // Act
-            await loader.LoadCurrentCultureResourcesAsync();
-            CultureInfo.CurrentCulture = new CultureInfo("fr-fr");
-            await loader.LoadCurrentCultureResourcesAsync();
-
-            invoker.Verify(i => i.InvokeUnmarshalled<object, object, object, Task<object>>(GetSatelliteAssemblies, It.IsAny<string[]>(), null, null),
-                Times.Exactly(2));
-        }
-
-        [Fact]
-        public async Task LoadCurrentCultureResourcesAsync_NoOps_WhenInvokedSecondTime_WithSameCulture()
-        {
-            // Arrange
-            using var cultureReplacer = new CultureReplacer("en-GB");
-            var invoker = new Mock<WebAssemblyJSRuntimeInvoker>();
-            invoker.Setup(i => i.InvokeUnmarshalled<string[], object, object, Task<object>>(GetSatelliteAssemblies, It.IsAny<string[]>(), null, null))
-                 .Returns(Task.FromResult<object>(0));;
-
-            var loader = new SatelliteResourcesLoader(invoker.Object);
-
-            // Act
-            await loader.LoadCurrentCultureResourcesAsync();
-            await loader.LoadCurrentCultureResourcesAsync();
-
-            invoker.Verify(i => i.InvokeUnmarshalled<object, object, object, Task<object>>(GetSatelliteAssemblies, It.IsAny<string[]>(), null, null),
-                Times.Once());
-        }
     }
 }

src/Components/WebAssembly/WebAssembly/test/Hosting/WebAssemblyHostTest.cs

@@ -99,7 +99,7 @@ internal TestSatelliteResourcesLoader()
             {
             }
 
-            protected override ValueTask LoadSatelliteAssembliesForCurrentCultureAsync() => default;
+            public override ValueTask LoadCurrentCultureResourcesAsync() => default;
         }
     }
 }