[Blazor] Add HTTP HEAD method support to RazorComponentEndpoints (#64613)

* Adds HEAD support for Blazor SSR.

Author: Copilot

src/Components/Endpoints/src/Builder/RazorComponentEndpointFactory.cs

@@ -15,7 +15,7 @@ namespace Microsoft.AspNetCore.Components.Endpoints;
 
 internal class RazorComponentEndpointFactory
 {
-    private static readonly HttpMethodMetadata HttpMethodsMetadata = new([HttpMethods.Get, HttpMethods.Post]);
+    private static readonly HttpMethodMetadata HttpMethodsMetadata = new([HttpMethods.Get, HttpMethods.Head, HttpMethods.Post]);
 
 #pragma warning disable CA1822 // It's a singleton
     internal void AddEndpoints(

src/Components/Endpoints/test/RazorComponentEndpointFactoryTest.cs

@@ -47,6 +47,7 @@ public void AddEndpoints_CreatesEndpointWithExpectedMetadata()
         var methods = Assert.Single(endpoint.Metadata.GetOrderedMetadata<HttpMethodMetadata>());
         Assert.Collection(methods.HttpMethods,
             method => Assert.Equal("GET", method),
+            method => Assert.Equal("HEAD", method),
             method => Assert.Equal("POST", method)
             );
     }

src/Components/Endpoints/test/RazorComponentEndpointInvokerTest.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Microsoft.AspNetCore.Components.Authorization;
+using Microsoft.AspNetCore.Components.Endpoints.Tests.TestComponents;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Routing;
@@ -51,6 +52,49 @@ public async Task Invoker_RejectsPostRequestsWithNonFormDataContentTypesAsync()
         Assert.Equal(StatusCodes.Status400BadRequest, context.Response.StatusCode);
     }
 
+    [Fact]
+    public async Task Invoker_HandlesHeadRequestAsync()
+    {
+        // Arrange
+        var services = new ServiceCollection().AddRazorComponents()
+                        .Services.AddAntiforgery()
+                        .AddSingleton<IConfiguration>(new ConfigurationBuilder().Build())
+                        .AddSingleton<IWebHostEnvironment>(new TestWebHostEnvironment())
+                        .BuildServiceProvider();
+
+        var invoker = new RazorComponentEndpointInvoker(
+            new EndpointHtmlRenderer(
+                services,
+                NullLoggerFactory.Instance),
+            NullLogger<RazorComponentEndpointInvoker>.Instance);
+
+        var context = new DefaultHttpContext();
+        context.SetEndpoint(new RouteEndpoint(
+            ctx => Task.CompletedTask,
+            RoutePatternFactory.Parse("/"),
+            0,
+            new EndpointMetadataCollection(
+                new ComponentTypeMetadata(typeof(SimpleComponent)),
+                new RootComponentMetadata(typeof(SimpleComponent)),
+                new ConfiguredRenderModesMetadata(Array.Empty<IComponentRenderMode>())),
+            "test"));
+        context.Request.Method = "HEAD";
+        context.Request.Scheme = "https";
+        context.Request.Host = new HostString("localhost");
+        context.Request.Path = "/";
+        context.Response.Body = new MemoryStream();
+        context.RequestServices = services;
+
+        // Act
+        await invoker.Render(context);
+
+        // Assert
+        // HEAD requests should execute the full request like GET, returning 200 OK with headers.
+        // The HTTP server (Kestrel) handles suppressing the response body for HEAD requests.
+        Assert.Equal(StatusCodes.Status200OK, context.Response.StatusCode);
+        Assert.Equal("text/html; charset=utf-8", context.Response.ContentType);
+    }
+
     private class TestWebHostEnvironment : IWebHostEnvironment
     {
         public string WebRootPath { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }

src/Components/test/E2ETest/Tests/GlobalInteractivityTest.cs

@@ -195,4 +195,21 @@ public void StatusCodePagesWithReExecution()
     }
     private void AssertReExecutedPageRendered() =>
         Browser.Equal("Welcome On Page Re-executed After Not Found Event", () => Browser.Exists(By.Id("test-info")).Text);
+
+    [Fact]
+    public async Task HeadRequestReturnsSuccessWithNoBody()
+    {
+        // Arrange
+        using var client = new HttpClient() { BaseAddress = _serverFixture.RootUri };
+        var request = new HttpRequestMessage(HttpMethod.Head, "/subdir/globally-interactive");
+
+        // Act
+        var response = await client.SendAsync(request);
+
+        // Assert
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal("text/html; charset=utf-8", response.Content.Headers.ContentType?.ToString());
+        var body = await response.Content.ReadAsStringAsync();
+        Assert.Empty(body);
+    }
 }