[release/11.0-preview6] Fix Blazor WASM Standalone HTTPS failure with Gateway (#67565)

* Fix Blazor WASM Standalone HTTPS failure with Gateway

The Blazor Gateway replaced the DevServer in #66729, switching from
Host.CreateDefaultBuilder (which auto-configures Kestrel HTTPS) to
WebApplication.CreateSlimBuilder (which does not). This caused
'blazorwasm' template projects to throw InvalidOperationException
when using an https:// launch profile URL.

Add UseKestrelHttpsConfiguration() to BlazorGateway.BuildWebHost so
Kestrel can bind HTTPS endpoints.

Fixes #67484

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Add Gateway HTTPS regression test

Co-authored-by: lewing <24063+lewing@users.noreply.github.com>

* Assert Gateway binds HTTPS in regression test

Co-authored-by: lewing <24063+lewing@users.noreply.github.com>

---------

Co-authored-by: Larry Ewing <lewing@gmail.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: lewing <24063+lewing@users.noreply.github.com>

Author: 4 people

src/Components/Gateway/src/BlazorGateway.cs

@@ -39,6 +39,7 @@ internal static WebApplication BuildWebHost(WebApplicationBuilder builder)
 
         builder.Services.AddServiceDiscovery();
 
+        builder.WebHost.UseKestrelHttpsConfiguration();
         builder.WebHost.UseStaticWebAssets();
 
         var appConfigs = builder.Configuration.GetSection("ClientApps")

src/Components/Gateway/test/BlazorGatewayTests.cs

@@ -198,6 +198,24 @@ public async Task ClientApps_ConfigEndpoint_ReturnsConfiguredJson()
         Assert.Equal(json, body, ignoreLineEndingDifferences: true);
     }
 
+    [Fact]
+    public async Task BuildWebHost_StartsWithHttpsUrl_WhenKestrelCertificateConfigured()
+    {
+        var testCertificatePath = Path.Combine(AppContext.BaseDirectory, "shared", "TestCertificates", "testCert.pfx");
+        var builder = WebApplication.CreateSlimBuilder(new[] { "--urls", "https://127.0.0.1:0" });
+        builder.Configuration.AddInMemoryCollection(new Dictionary<string, string?>
+        {
+            ["Kestrel:Certificates:Default:Path"] = testCertificatePath,
+            ["Kestrel:Certificates:Default:Password"] = "testPassword",
+        });
+
+        await using var app = BlazorGateway.BuildWebHost(builder);
+
+        await app.StartAsync();
+
+        Assert.Contains(app.Urls, address => address.StartsWith("https://127.0.0.1:", StringComparison.Ordinal));
+    }
+
     private static bool IsRedirect(HttpStatusCode status) =>
         status is HttpStatusCode.MovedPermanently
             or HttpStatusCode.Found

src/Components/Gateway/test/Microsoft.AspNetCore.Components.Gateway.Tests.csproj

@@ -21,6 +21,7 @@
     <Reference Include="Microsoft.Extensions.ServiceDiscovery" />
     <Reference Include="Microsoft.Extensions.ServiceDiscovery.Yarp" />
     <Reference Include="Yarp.ReverseProxy" />
+    <Content Include="$(SharedSourceRoot)TestCertificates\*.pfx" LinkBase="shared\TestCertificates" CopyToOutputDirectory="PreserveNewest" />
     <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="$(OpenTelemetryExporterOpenTelemetryProtocolVersion)" />
     <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="$(OpenTelemetryExtensionsHostingVersion)" />
     <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="$(OpenTelemetryInstrumentationAspNetCoreVersion)" />