Emitting OpenAPI about types created/returned by middleware in HTTP. …

…Also supports null for IResult in "before" middleware. Closes GH-1139

docs/guide/http/metadata.md

@@ -168,3 +168,9 @@ Any endpoint that returns `CreationResponse` or a sub class will automatically e
 processing to denote resource creation instead of the generic `200`. Same goes for the built-in `AcceptResponse` type, but returning `202` status. Your own custom implementations of the `IHttpAware`
 interface would apply the metadata declarations at configuration time so that those customizations would be part of the
 exported Swashbuckle documentation of the system.
+
+As of Wolverine 3.4, Wolverine will also apply OpenAPI metadata from any value created by compound handler middleware
+or other middleware that implements the `IEndpointMetadataProvider` interface -- which many `IResult` implementations
+from within ASP.Net Core middleware do. Consider this example from the tests:
+
+snippet: sample_using_optional_iresult_with_openapi_metadata

docs/guide/http/middleware.md

@@ -82,6 +82,11 @@ public static async Task<IResult> ExecuteOne<T>(IValidator<T> validator, IProble
 <sup><a href='https://github.com/JasperFx/wolverine/blob/main/src/Http/Wolverine.Http.FluentValidation/Internals/FluentValidationHttpExecutor.cs#L9-L29' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_fluentvalidationhttpexecutor_executeone' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
+Likewise, you can also just return a `null` from middleware for `IResult` and Wolverine will interpret that as
+"just continue" as shown in this sample:
+
+snippet: sample_using_optional_iresult_with_openapi_metadata
+
 ## Using Configure(chain) Methods
 
 You can make explicit modifications to HTTP processing for middleware or OpenAPI metadata for a single endpoint (really all

src/Http/Wolverine.Http.Tests/using_IResult_in_endpoints.cs

@@ -1,4 +1,5 @@
 using Shouldly;
+using WolverineWebApi.Validation;
 
 namespace Wolverine.Http.Tests;
 
@@ -31,4 +32,26 @@ public async Task use_as_return_value_async()
 
         result.ReadAsText().ShouldBe("Hello from async result");
     }
+
+    [Fact]
+    public async Task using_optional_result_in_middleware_when_result_is_null()
+    {
+        var result = await Scenario(x =>
+        {
+            x.Delete.Json(new BlockUser2("one")).ToUrl("/optional/result");
+            x.Header("content-type").SingleValueShouldEqual("text/plain");
+        });
+
+        result.ReadAsText().ShouldBe("Ok - user blocked");
+    }
+
+    [Fact]
+    public async Task using_optional_result_in_middleware_when_result_is_not_null()
+    {
+        var result = await Scenario(x =>
+        {
+            x.Delete.Json(new BlockUser2(null)).ToUrl("/optional/result");
+            x.StatusCodeShouldBe(404);
+        });
+    }
 }

src/Http/Wolverine.Http/CodeGen/ResultContinuationPolicy.cs

@@ -49,7 +49,7 @@ public override IEnumerable<Variable> FindVariables(IMethodVariables chain)
     public override void GenerateCode(GeneratedMethod method, ISourceWriter writer)
     {
         writer.WriteComment("Evaluate whether or not the execution should be stopped based on the IResult value");
-        writer.Write($"BLOCK:if (!({_result.Usage} is {typeof(WolverineContinue).FullNameInCode()}))");
+        writer.Write($"BLOCK:if ({_result.Usage} != null && !({_result.Usage} is {typeof(WolverineContinue).FullNameInCode()}))");
         writer.Write($"await {_result.Usage}.{nameof(IResult.ExecuteAsync)}({_context!.Usage}).ConfigureAwait(false);");
         writer.Write("return;");
         writer.FinishBlock();

src/Http/Wolverine.Http/HttpChain.EndpointBuilder.cs

@@ -1,3 +1,4 @@
+using System.Diagnostics;
 using System.Reflection;
 using JasperFx.CodeGeneration;
 using JasperFx.Core;
@@ -80,6 +81,11 @@ public RouteEndpoint BuildEndpoint()
             tryApplyAsEndpointMetadataProvider(parameter.ParameterType, builder);
         }
 
+        foreach (var created in Middleware.SelectMany(x => x.Creates))
+        {
+            tryApplyAsEndpointMetadataProvider(created.VariableType, builder);
+        }
+
         // Set up OpenAPI data for ProblemDetails with status code 400 if not already exists
         if (Middleware.SelectMany(x => x.Creates).Any(x => x.VariableType == typeof(ProblemDetails)))
         {

src/Http/WolverineWebApi/ResultEndpoints.cs

@@ -16,4 +16,6 @@ public static Task<IResult> GetAsyncResult()
         var result = Microsoft.AspNetCore.Http.Results.Content("Hello from async result", "text/plain");
         return Task.FromResult(result);
     }
+
+
 }

src/Http/WolverineWebApi/Validation/ValidatedCompoundEndpoint.cs

@@ -1,4 +1,6 @@
 using FluentValidation;
+using JasperFx.Core;
+using Microsoft.AspNetCore.Http.HttpResults;
 using Wolverine.Http;
 
 namespace WolverineWebApi.Validation;
@@ -28,7 +30,38 @@ public static  string Handle(BlockUser cmd, User user)
     }
 }
 
+#region sample_using_optional_iresult_with_openapi_metadata
+
+public class ValidatedCompoundEndpoint2
+{
+    public static User? Load(BlockUser2 cmd)
+    {
+        return cmd.UserId.IsNotEmpty() ? new User(cmd.UserId) : null;
+    }
+
+    // This method would be called, and if the NotFound value is
+    // not null, will stop the rest of the processing
+    // Likewise, Wolverine will use the NotFound type to add
+    // OpenAPI metadata
+    public static NotFound? Validate(User? user)
+    {
+        if (user == null)
+            return (NotFound?)Results.NotFound<User>(user);
+
+        return null;
+    }
+
+    [WolverineDelete("/optional/result")]
+    public static  string Handle(BlockUser2 cmd, User user)
+    {
+        return "Ok - user blocked";
+    }
+}
+
+#endregion
+
 public record BlockUser(string? UserId);
+public record BlockUser2(string? UserId);
 
 public class BlockUserValidator : AbstractValidator<BlockUser>
 {