[Extensions] Fix ASP.NET Core integration testing (#48426)

* [Extensions] Fix ASP.NET Core integration testing

The focus of these changes is to fix an assumption
in the logic when creating clients from configuration.
Currently, if the configuration section has a non-null
value, it is assumed to be a connection string.
This is not the case for ASP.NET Core test integration
due to a bug in the test host which causes the Value
property to return an empty string rather than the
null returned by the actual configuration system.

sdk/extensions/Microsoft.Extensions.Azure/CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### Bugs Fixed
 
+- Fixed an issue when creating clients from configuration using the ASP.NET Core integration testing library, `Microsoft.AspNetCore.Mvc.Testing`.  Due to a difference in how an section value is represented, logic was interpreting a setting with a child object as an empty connection string value.  The child object is now properly parsed and applied for client construction.  ([#48368](https://github.com/Azure/azure-sdk-for-net/issues/48368))
+
 ### Other Changes
 
 ## 1.10.0 (2025-02-11)

sdk/extensions/Microsoft.Extensions.Azure/src/Internal/ClientFactory.cs

@@ -30,14 +30,14 @@ public static object CreateClient(
         {
             List<object> arguments = new List<object>();
             // Handle single values as connection strings
-            if (configuration is IConfigurationSection section && section.Value != null)
+            if (configuration is IConfigurationSection section && (!string.IsNullOrEmpty(section.Value)))
             {
                 var connectionString = section.Value;
                 configuration = new ConfigurationBuilder()
-                    .AddInMemoryCollection(new[]
-                    {
+                    .AddInMemoryCollection(
+                    [
                         new KeyValuePair<string, string>(ConnectionStringParameterName, connectionString)
-                    })
+                    ])
                     .Build();
             }
             foreach (var constructor in clientType.GetConstructors().OrderByDescending(c => c.GetParameters().Length))

sdk/extensions/Microsoft.Extensions.Azure/src/Microsoft.Extensions.Azure.csproj

@@ -25,7 +25,7 @@
     <PackageReference Include="Microsoft.Extensions.Options" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Binder" />
-		<PackageReference Include="Microsoft.Bcl.AsyncInterfaces" VersionOverride="8.0.0" />
+    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" VersionOverride="8.0.0" />
   </ItemGroup>
 
   <ItemGroup>

sdk/extensions/Microsoft.Extensions.Azure/tests/ClientFactoryTests.cs

@@ -12,6 +12,13 @@
 using Microsoft.Extensions.Configuration;
 using NUnit.Framework;
 
+#if NET8_0_OR_GREATER
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.AspNetCore.TestHost;
+#endif
+
 namespace Azure.Core.Extensions.Tests
 {
     public class ClientFactoryTests
@@ -626,6 +633,37 @@ public void CanUseAzureSasCredential()
             Assert.AreEqual("key", client.AzureSasCredential.Signature);
         }
 
+#if NET8_0_OR_GREATER
+        [Test]
+        public async Task AllowsAspNetCoreIntegrationTestHostConfiguration()
+        {
+            var expectedKeyVaultUriValue = "https://fake.vault.azure.net/";
+
+            // When configuration is set using the test host, the behavior of IConfigurationSection
+            // changes and the Value property is not null for a complex object.  Instead it returns an
+            // empty string, which we don't want to treat as a connection string.
+            //
+            // This is a bug in the configuration system, but there's no commitment for when it will
+            // be fixed.  See: https://github.com/dotnet/aspnetcore/issues/37680
+            //
+            var factory = new WebApplicationFactory<AspNetHost>()
+                .WithWebHostBuilder(builder =>
+                {
+                    builder.UseContentRoot("aspnet-host");
+
+                    builder.UseConfiguration(
+                        GetConfiguration(
+                            new KeyValuePair<string, string>("KeyVault:VaultUri", expectedKeyVaultUriValue)));
+                });
+
+            var client = factory.CreateClient();
+            var response = await client.GetAsync("/keyvault");
+            var keyVaultUriValue = await response.Content.ReadAsStringAsync();
+
+            Assert.AreEqual(expectedKeyVaultUriValue, keyVaultUriValue);
+        }
+#endif
+
         private IConfiguration GetConfiguration(params KeyValuePair<string, string>[] items)
         {
             return new ConfigurationBuilder().AddInMemoryCollection(items).Build();

sdk/extensions/Microsoft.Extensions.Azure/tests/Microsoft.Extensions.Azure.Tests.csproj

@@ -2,19 +2,50 @@
   <PropertyGroup>
     <TargetFrameworks>$(RequiredTargetFrameworks)</TargetFrameworks>
   </PropertyGroup>
+  <ItemGroup>
+    <None Include="aspnet-host\AspNetHostRoot.sln" />
+  </ItemGroup>
 
   <ItemGroup>
-		<PackageReference Include="Microsoft.Extensions.DependencyInjection" VersionOverride="8.0.1" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" VersionOverride="8.0.1" />
+    <PackageReference Include="Microsoft.Extensions.PlatformAbstractions" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
-    <PackageReference Include="System.Net.WebSockets.Client" />
-    <PackageReference Include="System.ValueTuple" />
     <PackageReference Include="NUnit" />
     <PackageReference Include="NUnit3TestAdapter" />
-    <PackageReference Include="Microsoft.Extensions.PlatformAbstractions" />
+    <PackageReference Include="System.Net.WebSockets.Client" />
+    <PackageReference Include="System.ValueTuple" />
   </ItemGroup>
 
   <ItemGroup>
     <ProjectReference Include="$(AzureCoreTestFramework)" />
     <ProjectReference Include="..\src\Microsoft.Extensions.Azure.csproj" />
   </ItemGroup>
+
+  <!-- Include ASPNET content for testing compatibility with the integration framework on net8+ only -->
+  <ItemGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))">
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+    <PackageReference Include="Azure.Security.KeyVault.Secrets" />
+
+    <!--
+      Override the ASPNET Core testing package locally until the 8.x bump in the engineering system.
+      Tracked by: #48425
+    -->
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="8.0.13" />
+  </ItemGroup>
+
+  <!-- Don't include the generated entry point for net8+ because one is explicitly defined in the ASPNET content -->
+  <PropertyGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))">
+    <GenerateProgramFile>false</GenerateProgramFile>
+  </PropertyGroup>
+
+  <!-- Include the solution and content root markers for the ASPNET Core application -->
+  <Target Name="CopyCustomContent" AfterTargets="AfterBuild">
+    <Copy SourceFiles="aspnet-host\AspNetHostRoot.sln" DestinationFolder="$(OutDir)" />
+  </Target>
+
+  <ItemGroup>
+    <None Update="aspnet-host\appsettings.json">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
 </Project>

sdk/extensions/Microsoft.Extensions.Azure/tests/aspnet-host/AspNetHost.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#if NET8_0_OR_GREATER
+
+using Azure.Security.KeyVault.Secrets;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.Azure;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Azure.Core.Extensions.Tests;
+
+public class AspNetHost
+{
+    public static void Main(string[] args)
+    {
+        var builder = WebApplication.CreateBuilder(args);
+        builder.Environment.ContentRootPath = "aspnet-host";
+
+        builder.Services.AddAzureClients(clientBuilder =>
+        {
+            clientBuilder.AddSecretClient(builder.Configuration.GetSection("KeyVault"));
+        });
+
+        var app = builder.Build();
+        var secretClient = app.Services.GetRequiredService<SecretClient>();
+
+        app.MapGet("/keyvault", () => secretClient.VaultUri.AbsoluteUri);
+        app.Run();
+    }
+}
+#endif

sdk/extensions/Microsoft.Extensions.Azure/tests/aspnet-host/appsettings.json

@@ -0,0 +1,12 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*",
+  "KeyVault": {
+    "VaultUri": "<vault_uri>"
+  }
+}