Fail at startup when ASP.NET OpenAPI is registered

Author: bkoelman

src/JsonApiDotNetCore/Configuration/ApplicationBuilderExtensions.cs

@@ -1,6 +1,7 @@
 using JsonApiDotNetCore.Middleware;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
 
 namespace JsonApiDotNetCore.Configuration;
 
@@ -23,6 +24,7 @@ public static class ApplicationBuilderExtensions
  public static void UseJsonApi(this IApplicationBuilder builder)
  {
  ArgumentNullException.ThrowIfNull(builder);
+ AssertAspNetCoreOpenApiIsNotRegistered(builder.ApplicationServices);
 
  using (IServiceScope scope = builder.ApplicationServices.CreateScope())
  {
@@ -46,4 +48,33 @@ public static void UseJsonApi(this IApplicationBuilder builder)
 
  builder.UseMiddleware<JsonApiMiddleware>();
  }
+
+ private static void AssertAspNetCoreOpenApiIsNotRegistered(IServiceProvider serviceProvider)
+ {
+ Type? optionsType = TryLoadOptionsType();
+
+ if (optionsType != null)
+ {
+ Type configureType = typeof(IConfigureOptions<>).MakeGenericType(optionsType);
+ object? configureInstance = serviceProvider.GetService(configureType);
+
+ if (configureInstance != null)
+ {
+ throw new InvalidOperationException("JsonApiDotNetCore is incompatible with ASP.NET OpenAPI. " +
+ "Replace 'services.AddOpenApi()' with 'services.AddOpenApiForJsonApi()' from the JsonApiDotNetCore.OpenApi.Swashbuckle NuGet package.");
+ }
+ }
+ }
+
+ private static Type? TryLoadOptionsType()
+ {
+ try
+ {
+ return Type.GetType("Microsoft.AspNetCore.OpenApi.OpenApiOptions, Microsoft.AspNetCore.OpenApi");
+ }
+ catch (FileLoadException)
+ {
+ return null;
+ }
+ }
 }

test/DiscoveryTests/AspNetOpenApiTests.cs

@@ -0,0 +1,31 @@
+#if !NET8_0
+using FluentAssertions;
+using JsonApiDotNetCore.Configuration;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit;
+
+namespace DiscoveryTests;
+
+public sealed class AspNetOpenApiTests
+{
+ [Fact]
+ public async Task Throws_when_AspNet_OpenApi_is_registered()
+ {
+ // Arrange
+ WebApplicationBuilder builder = WebApplication.CreateEmptyBuilder(new WebApplicationOptions());
+ builder.WebHost.UseTestServer();
+ builder.Services.AddJsonApi();
+ builder.Services.AddOpenApi();
+ await using WebApplication app = builder.Build();
+
+ // Act
+ Action action = app.UseJsonApi;
+
+ // Assert
+ action.Should().ThrowExactly<InvalidOperationException>().WithMessage("JsonApiDotNetCore is incompatible with ASP.NET OpenAPI. " +
+ "Replace 'services.AddOpenApi()' with 'services.AddOpenApiForJsonApi()' from the JsonApiDotNetCore.OpenApi.Swashbuckle NuGet package.");
+ }
+}
+#endif

test/DiscoveryTests/DiscoveryTests.csproj

@@ -14,5 +14,6 @@
  <PackageReference Include="coverlet.collector" Version="$(CoverletVersion)" PrivateAssets="All" />
  <PackageReference Include="GitHubActionsTestLogger" Version="$(GitHubActionsTestLoggerVersion)" PrivateAssets="All" />
  <PackageReference Include="Microsoft.NET.Test.Sdk" Version="$(TestSdkVersion)" />
+ <PackageReference Include="Microsoft.AspNetCore.OpenApi" Condition="'$(TargetFramework)' != 'net8.0'" Version="$(AspNetCoreVersion)" />
  </ItemGroup>
 </Project>