Update OpenApi implementation to avoid reflection

Author: Youssef1313

examples/AspNetCore/WebApi/MinimalOpenApiExample/MinimalOpenApiExample.csproj

@@ -4,6 +4,9 @@
   <TargetFramework>net10.0</TargetFramework>
   <AssemblyTitle>Example API</AssemblyTitle>
   <GenerateDocumentationFile>true</GenerateDocumentationFile>
+  <InterceptorsNamespaces>$(InterceptorsNamespaces);Microsoft.AspNetCore.OpenApi.Generated</InterceptorsNamespaces>
+  <OpenApiGenerateDocuments>false</OpenApiGenerateDocuments>
+  <OpenApiGenerateDocumentsOnBuild>false</OpenApiGenerateDocumentsOnBuild>
  </PropertyGroup>
 
  <ItemGroup>

src/AspNetCore/WebApi/src/Asp.Versioning.OpenApi/Builder/IEndpointConventionBuilderExtensions.cs

@@ -6,7 +6,6 @@ namespace Microsoft.AspNetCore.Builder;
 
 using Asp.Versioning;
 using Asp.Versioning.ApiExplorer;
-using Asp.Versioning.OpenApi.Reflection;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
@@ -44,12 +43,12 @@ private static void ApplyApiVersioning( EndpointBuilder builder )
 
     private static Task InterceptRequestServices( HttpContext context, RequestDelegate action )
     {
-        if ( context.RequestServices is not KeyedServiceContainer requestServices )
+        if ( context.RequestServices is not AggregateKeyedServiceProvider serviceProvider )
         {
-            requestServices = context.RequestServices.GetRequiredService<KeyedServiceContainer>();
+            serviceProvider = context.RequestServices.GetRequiredService<AggregateKeyedServiceProvider>();
         }
 
-        context.RequestServices = requestServices;
+        context.RequestServices = serviceProvider;
         return action( context );
     }
 }

src/AspNetCore/WebApi/src/Asp.Versioning.OpenApi/Configuration/ConfigureOpenApiOptions.cs

@@ -5,10 +5,11 @@
 namespace Asp.Versioning.OpenApi.Configuration;
 
 using Asp.Versioning.ApiExplorer;
-using Asp.Versioning.OpenApi.Reflection;
 using Asp.Versioning.OpenApi.Transformers;
 using Microsoft.AspNetCore.OpenApi;
 using Microsoft.Extensions.Options;
+using System.Net;
+using System.Runtime.CompilerServices;
 
 internal sealed class ConfigureOpenApiOptions(
     XmlCommentsTransformer xmlComments,
@@ -48,7 +49,7 @@ private static void Configure( VersionedOpenApiOptions versionedOptions, XmlComm
         var options = versionedOptions.Document;
         var apiExplorer = new ApiExplorerTransformer( versionedOptions );
 
-        options.SetDocumentName( versionedOptions.Description.GroupName );
+        SetDocumentName( options, versionedOptions.Description.GroupName );
         options.AddDocumentTransformer( apiExplorer );
         options.AddSchemaTransformer( apiExplorer );
         options.AddOperationTransformer( apiExplorer );
@@ -59,4 +60,7 @@ private static void Configure( VersionedOpenApiOptions versionedOptions, XmlComm
             options.AddOperationTransformer( xmlComments );
         }
     }
+
+    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "set_DocumentName")]
+    private static extern void SetDocumentName( OpenApiOptions handler, string value );
 }

src/AspNetCore/WebApi/src/Asp.Versioning.OpenApi/DependencyInjection/AggregateKeyedServiceProvider.cs

@@ -0,0 +1,60 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+
+#pragma warning disable IDE0130
+
+namespace Microsoft.Extensions.DependencyInjection;
+
+internal sealed class AggregateKeyedServiceProvider( IServiceProvider parent ) : IKeyedServiceProvider
+{
+    private readonly IServiceProvider parent = parent;
+    private readonly List<IServiceProvider> providers = [];
+
+    public object? GetKeyedService( Type serviceType, object? serviceKey )
+    {
+        if ( providers.Count == 0 )
+        {
+            return parent.GetKeyedService( serviceType, serviceKey );
+        }
+
+        foreach ( var provider in providers )
+        {
+            if ( provider.GetKeyedService( serviceType, serviceKey ) is { } service )
+            {
+                return service;
+            }
+        }
+
+        return null;
+    }
+
+    public object GetRequiredKeyedService( Type serviceType, object? serviceKey )
+    {
+        if ( providers.Count == 0 )
+        {
+            return parent.GetRequiredKeyedService( serviceType, serviceKey );
+        }
+
+        for ( int i = 0; i < providers.Count - 1; i++ )
+        {
+            if ( providers[i].GetKeyedService( serviceType, serviceKey ) is { } service )
+            {
+                return service;
+            }
+        }
+
+        return providers[providers.Count - 1].GetRequiredKeyedService( serviceType, serviceKey );
+    }
+
+    public object? GetService( Type serviceType )
+        => parent.GetService( serviceType );
+
+    public void Add( IServiceCollection serviceCollection, IServiceCollection parentServiceCollection )
+    {
+        foreach ( var descriptor in parentServiceCollection )
+        {
+            serviceCollection.Add( descriptor );
+        }
+
+        providers.Add( serviceCollection.BuildServiceProvider() );
+    }
+}

src/AspNetCore/WebApi/src/Asp.Versioning.OpenApi/DependencyInjection/IApiVersioningBuilderExtensions.cs

@@ -8,13 +8,14 @@ namespace Microsoft.Extensions.DependencyInjection;
 using Asp.Versioning.ApiExplorer;
 using Asp.Versioning.OpenApi;
 using Asp.Versioning.OpenApi.Configuration;
-using Asp.Versioning.OpenApi.Reflection;
 using Asp.Versioning.OpenApi.Transformers;
 using Microsoft.AspNetCore.Http.Json;
 using Microsoft.AspNetCore.OpenApi;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Options;
+using System.ComponentModel.Design;
+using System.Diagnostics;
 using System.Reflection;
 using static Microsoft.Extensions.DependencyInjection.ServiceDescriptor;
 using EM = Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions;
@@ -56,26 +57,22 @@ public IApiVersioningBuilder AddOpenApi( Action<VersionedOpenApiOptions> configu
             return builder;
         }
     }
-
+#pragma warning disable
     [UnconditionalSuppressMessage( "ILLink", "IL2026" )]
     private static void AddOpenApiServices( IApiVersioningBuilder builder, Assembly[] assemblies )
     {
         builder.AddApiExplorer();
 
         var services = builder.Services;
 
-        services.AddTransient( NewRequestServices );
-        services.Add( Singleton( Type.IDocumentProvider, ResolveDocumentProvider ) );
+        services.AddTransient( serviceProvider => NewRequestServices( serviceProvider, services ) );
+        // services.AddOpenApi();
+
         services.AddSingleton<VersionedOpenApiOptionsFactory>();
-        services.TryAddEnumerable( Transient<IPostConfigureOptions<OpenApiOptions>, ConfigureOpenApiOptions>() );
         services.TryAdd( Singleton<IOptionsFactory<VersionedOpenApiOptions>>( EM.GetRequiredService<VersionedOpenApiOptionsFactory> ) );
         services.AddTransient( sp => new XmlCommentsFile( assemblies, sp.GetRequiredService<IHostEnvironment>() ) );
         services.TryAddTransient( sp => new XmlCommentsTransformer( sp.GetRequiredService<XmlCommentsFile>() ) );
 
-        if ( GetJsonConfiguration() is { } descriptor )
-        {
-            services.TryAddEnumerable( descriptor );
-        }
     }
 
     // NOTE: The calling assembly must be captured at the call site that invokes AddOpenApi. In 99% of the cases that
@@ -94,53 +91,19 @@ private static Assembly[] GetAssemblies( Assembly callingAssembly )
         return [.. assemblies];
     }
 
-    // HACK: the json configuration is internal; this approach negates the use of reflection
-    // REF: https://github.com/dotnet/aspnetcore/blob/08a9fc2c3864d99759ab3d71cfda868d852bfc4b/src/OpenApi/src/Extensions/OpenApiServiceCollectionExtensions.cs#L121
-    private static ServiceDescriptor? GetJsonConfiguration()
-    {
-        var services = new ServiceCollection();
-        services.AddOpenApi( "*" );
-        return services.SingleOrDefault( sd => sd.ServiceType == typeof( IConfigureOptions<JsonOptions> ) );
-    }
-
-    private static object ResolveDocumentProvider( IServiceProvider provider ) =>
-        provider.GetRequiredService<KeyedServiceContainer>().GetRequiredService( Type.IDocumentProvider );
-
     [UnconditionalSuppressMessage( "ILLink", "IL3050" )]
-    private static KeyedServiceContainer NewRequestServices( IServiceProvider services )
+    private static AggregateKeyedServiceProvider NewRequestServices( IServiceProvider services, IServiceCollection parentServiceCollection )
     {
         var provider = services.GetRequiredService<IApiVersionDescriptionProvider>();
-        var container = new KeyedServiceContainer( services );
-        var type = typeof( IOpenApiDocumentProvider );
+        var container = new AggregateKeyedServiceProvider( services );
         var descriptions = provider.ApiVersionDescriptions;
-        var names = new List<string>( descriptions.Count );
 
         for ( var i = 0; i < descriptions.Count; i++ )
         {
             var description = descriptions[i];
-
-            // REF: https://github.com/dotnet/aspnetcore/blob/319e87fd950a99f3baae2aa79db3d4fb68783d85/src/OpenApi/src/Extensions/OpenApiServiceCollectionExtensions.cs#L64
-#pragma warning disable CA1308 // Normalize strings to uppercase
-            var key = description.GroupName.ToLowerInvariant();
-#pragma warning restore CA1308
-
-            names.Add( key );
-            container.AddService( Type.OpenApiSchemaService, key, Class.OpenApiSchemaService.New );
-            container.AddService( Type.OpenApiDocumentService, key, Class.OpenApiDocumentService.New );
-            container.AddService( type, key, ( sp, k ) => sp.GetRequiredKeyedService( Type.OpenApiDocumentService, k ) );
-        }
-
-        if ( names.Count > 0 )
-        {
-            var array = Array.CreateInstance( Type.NamedService, names.Count );
-
-            for ( var i = 0; i < names.Count; i++ )
-            {
-                array.SetValue( Class.NamedService.New( names[i] ), i );
-            }
-
-            container.AddService( Type.IDocumentProvider, Class.OpenApiDocumentProvider.New );
-            container.AddService( Type.IEnumerableOfNamedService, array );
+            var serviceCollection = new ServiceCollection();
+            serviceCollection.AddOpenApi( description.GroupName );
+            container.Add( serviceCollection, parentServiceCollection );
         }
 
         return container;