Detect trimming issues in CI

src/Components/Components/src/PublicAPI.Unshipped.txt

@@ -23,6 +23,8 @@ Microsoft.AspNetCore.Components.ResourceAssetProperty
 Microsoft.AspNetCore.Components.ResourceAssetProperty.Name.get -> string!
 Microsoft.AspNetCore.Components.ResourceAssetProperty.ResourceAssetProperty(string! name, string! value) -> void
 Microsoft.AspNetCore.Components.ResourceAssetProperty.Value.get -> string!
+Microsoft.AspNetCore.Components.UnusedTypeLoader
+static Microsoft.AspNetCore.Components.UnusedTypeLoader.LoadUnusedType() -> System.Type?
 static readonly Microsoft.AspNetCore.Components.ResourceAssetCollection.Empty -> Microsoft.AspNetCore.Components.ResourceAssetCollection!
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.Assets.get -> Microsoft.AspNetCore.Components.ResourceAssetCollection!
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.RendererInfo.get -> Microsoft.AspNetCore.Components.RendererInfo!

src/Components/Components/src/UnusedTypeForTrimming.cs

@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Components;
+
+/// <summary>
+/// For testing.
+/// </summary>
+public static class UnusedTypeLoader
+{
+    /// <summary>
+    /// For testing.
+    /// </summary>
+    public static Type? LoadUnusedType()
+    {
+        // We're intentionally loading an unreferenced type here.
+        // This should return null on a published build.
+
+#pragma warning disable IL2026 // Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code
+        return typeof(UnusedTypeLoader).Assembly.GetType($"Microsoft.AspNetCore.Components.{nameof(UnusedTypeForTrimming)}")!;
+#pragma warning restore IL2026 // Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code
+    }
+}
+
+internal sealed class UnusedTypeForTrimming
+{
+    public string UnusedProperty { get; } = "Foo";
+}

src/Components/test/testassets/BasicTestApp/Program.cs

@@ -22,6 +22,13 @@ public static async Task Main(string[] args)
     {
         await SimulateErrorsIfNeededForTest();
 
+        if (UnusedTypeLoader.LoadUnusedType() is null)
+        {
+            // Fail quickly if loading an unreferenced type fails.
+            // This should make it obvious if trimming issues get caught by E2E tests.
+            throw new InvalidOperationException("Could not load the type dynamically!");
+        }
+
         var builder = WebAssemblyHostBuilder.CreateDefault(args);
         builder.RootComponents.Add<HeadOutlet>("head::after");
         builder.RootComponents.Add<Index>("root");