Unwrap ValueTask<T> return types (#4374)

* Unwrap ValueTask<T> return types, same as Task<T>, unwrap (Value)Task<ActionResult<T>> and unify unwrapping for consistency #4373

* lahma suggestion for performance

Author: alasdaircs

src/NSwag.Generation.AspNetCore.Tests.Web/Controllers/Responses/WrappedResponseController.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Threading.Tasks;
+
+using Microsoft.AspNetCore.Mvc;
+
+using NSwag.Annotations;
+
+namespace NSwag.Generation.AspNetCore.Tests.Web.Controllers.Responses
+{
+    [ApiController]
+    [Route( "api/wrappedresponse" )]
+    public class WrappedResponseController : Controller
+    {
+
+        [HttpGet( "task" )]
+        public async Task Task()
+        {
+            throw new NotImplementedException();
+        }
+
+        [HttpGet( "int" )]
+        public int Int()
+        {
+            throw new NotImplementedException();
+        }
+
+        [HttpGet( "taskofint" )]
+        public async Task<int> TaskOfInt()
+        {
+            throw new NotImplementedException();
+        }
+
+        [HttpGet( "valuetaskofint" )]
+        public async ValueTask<int> ValueTaskOfInt()
+        {
+            throw new NotImplementedException();
+        }
+
+        [HttpGet( "actionresultofint" )]
+        public ActionResult<int> ActionResultOfInt()
+        {
+            throw new NotImplementedException();
+        }
+
+        [HttpGet( "taskofactionresultofint" )]
+        public async Task<ActionResult<int>> TaskOfActionResultOfInt()
+        {
+            throw new NotImplementedException();
+        }
+
+        [HttpGet( "valuetaskofactionresultofint" )]
+        public async ValueTask<ActionResult<int>> ValueTaskOfActionResultOfInt()
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

src/NSwag.Generation.AspNetCore.Tests/Responses/WrappedResponseTests.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+
+using Xunit;
+
+using NJsonSchema;
+
+using NSwag.Generation.AspNetCore.Tests.Web.Controllers.Responses;
+
+namespace NSwag.Generation.AspNetCore.Tests.Responses
+{
+    public class WrappedResponseTests : AspNetCoreTestsBase
+    {
+        [Fact]
+        public async Task When_response_is_wrapped_in_certain_generic_result_types_then_discard_the_wrapper_type()
+        {
+            // Arrange
+            var settings = new AspNetCoreOpenApiDocumentGeneratorSettings();
+
+            // Act
+            var document = await GenerateDocumentAsync(settings, typeof(WrappedResponseController));            
+            
+            // Assert
+            OpenApiResponse GetOperationResponse(String ActionName)
+                => document.Operations.Where(op => op.Operation.OperationId == $"{nameof(WrappedResponseController).Substring(0, nameof(WrappedResponseController).Length - "Controller".Length )}_{ActionName}").Single().Operation.ActualResponses.Single().Value;
+            JsonObjectType GetOperationResponseSchemaType( String ActionName )
+                => GetOperationResponse( ActionName ).Schema.Type;
+            var IntType = JsonSchema.FromType<int>().Type;
+
+            Assert.Null(GetOperationResponse(nameof(WrappedResponseController.Task)).Schema);
+            Assert.Equal(IntType, GetOperationResponseSchemaType(nameof( WrappedResponseController.Int)));
+            Assert.Equal(IntType, GetOperationResponseSchemaType(nameof( WrappedResponseController.TaskOfInt)));
+            Assert.Equal(IntType, GetOperationResponseSchemaType(nameof( WrappedResponseController.ValueTaskOfInt)));
+            Assert.Equal(IntType, GetOperationResponseSchemaType(nameof( WrappedResponseController.ActionResultOfInt)));
+            Assert.Equal(IntType, GetOperationResponseSchemaType(nameof( WrappedResponseController.TaskOfActionResultOfInt)));
+            Assert.Equal(IntType, GetOperationResponseSchemaType(nameof( WrappedResponseController.ValueTaskOfActionResultOfInt)));
+        }
+    }
+}

src/NSwag.Generation.WebApi.Tests/WrappedResponseTests.cs

@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using System.Web.Http;
+using System.Web.Http.Results;
+
+using CoreMvc = Microsoft.AspNetCore.Mvc;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+using NJsonSchema;
+
+
+namespace NSwag.Generation.WebApi.Tests
+{
+    [TestClass]
+    public class WrappedResponseTests
+    {
+        public class WrappedResponseController : ApiController
+        {
+            [HttpGet, Route( "task" )]
+            public Task Task()
+            {
+                throw new NotImplementedException();
+            }
+
+            [HttpGet, Route( "int" )]
+            public int Int()
+            {
+                throw new NotImplementedException();
+            }
+
+            [HttpGet, Route( "taskofint" )]
+            public Task<int> TaskOfInt()
+            {
+                throw new NotImplementedException();
+            }
+
+            [HttpGet, Route( "valuetaskofint" )]
+            public ValueTask<int> ValueTaskOfInt()
+            {
+                throw new NotImplementedException();
+            }
+
+            [HttpGet, Route( "jsonresultofint" )]
+            public JsonResult<int> JsonResultOfInt()
+            {
+                throw new NotImplementedException();
+            }
+
+            [HttpGet, Route( "actionresultofint" )]
+            public CoreMvc.ActionResult<int> ActionResultOfInt()
+            {
+                throw new NotImplementedException();
+            }
+            
+        }
+
+        [TestMethod]
+        public async Task When_response_is_wrapped_in_certain_generic_result_types_then_discard_the_wrapper_type()
+        {
+            // Arrange
+            var generator = new WebApiOpenApiDocumentGenerator( new WebApiOpenApiDocumentGeneratorSettings() );
+
+            // Act
+            var document = await generator.GenerateForControllerAsync<WrappedResponseController>();
+
+            // Assert
+            OpenApiResponse GetOperationResponse( String ActionName )
+                => document.Operations.Where( op => op.Operation.OperationId == $"{nameof(WrappedResponseController).Substring(0,nameof(WrappedResponseController).Length - "Controller".Length )}_{ActionName}" ).Single().Operation.ActualResponses.Single().Value;
+            JsonObjectType GetOperationResponseSchemaType( String ActionName )
+                => GetOperationResponse( ActionName ).Schema.Type;
+            var IntType = JsonSchema.FromType<int>().Type;
+
+            Assert.IsNull( GetOperationResponse( nameof( WrappedResponseController.Task ) ).Schema );
+            Assert.AreEqual( IntType, GetOperationResponseSchemaType( nameof( WrappedResponseController.Int ) ) );
+            Assert.AreEqual( IntType, GetOperationResponseSchemaType( nameof( WrappedResponseController.TaskOfInt ) ) );
+            Assert.AreEqual( IntType, GetOperationResponseSchemaType( nameof( WrappedResponseController.ValueTaskOfInt ) ) );
+            Assert.AreEqual( IntType, GetOperationResponseSchemaType( nameof( WrappedResponseController.JsonResultOfInt ) ) );
+            Assert.AreEqual( IntType, GetOperationResponseSchemaType( nameof( WrappedResponseController.ActionResultOfInt ) ) );
+
+        }
+    }
+}

src/NSwag.Generation/GenericResultWrapperTypes.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Linq;
+
+namespace NSwag.Generation
+{
+    internal static class GenericResultWrapperTypes
+    {
+        internal static bool IsGenericWrapperType( string typeName )
+            =>
+                typeName == "Task`1" ||
+                typeName == "ValueTask`1" ||
+                typeName == "JsonResult`1" ||
+                typeName == "ActionResult`1"
+            ;
+
+        internal static void RemoveGenericWrapperTypes<T>(ref T o, Func<T,string> getName, Func<T,T> unwrap)
+        {
+            // We iterate because a common signature is public async Task<ActionResult<T>> Action()
+            while (IsGenericWrapperType(getName(o)))
+            {
+                o = unwrap(o);
+            }
+        }
+    }
+}

src/NSwag.Generation/OpenApiSchemaGenerator.cs

@@ -51,29 +51,18 @@ protected override void GenerateObject(JsonSchema schema, JsonTypeDescription ty
             }
         }
 
-        /// <summary>Generetes a schema directly or referenced for the requested schema type; also adds nullability if required.</summary>
-        /// <typeparam name="TSchemaType">The resulted schema type which may reference the actual schema.</typeparam>
-        /// <param name="contextualType">The type of the schema to generate.</param>
-        /// <param name="isNullable">Specifies whether the property, parameter or requested schema type is nullable.</param>
-        /// <param name="schemaResolver">The schema resolver.</param>
-        /// <param name="transformation">An action to transform the resulting schema (e.g. property or parameter) before the type of reference is determined (with $ref or allOf/oneOf).</param>
-        /// <returns>The requested schema object.</returns>
-        public override TSchemaType GenerateWithReferenceAndNullability<TSchemaType>(
+		/// <summary>Generetes a schema directly or referenced for the requested schema type; also adds nullability if required.</summary>
+		/// <typeparam name="TSchemaType">The resulted schema type which may reference the actual schema.</typeparam>
+		/// <param name="contextualType">The type of the schema to generate.</param>
+		/// <param name="isNullable">Specifies whether the property, parameter or requested schema type is nullable.</param>
+		/// <param name="schemaResolver">The schema resolver.</param>
+		/// <param name="transformation">An action to transform the resulting schema (e.g. property or parameter) before the type of reference is determined (with $ref or allOf/oneOf).</param>
+		/// <returns>The requested schema object.</returns>
+		public override TSchemaType GenerateWithReferenceAndNullability<TSchemaType>(
             ContextualType contextualType, bool isNullable,
             JsonSchemaResolver schemaResolver, Action<TSchemaType, JsonSchema> transformation = null)
         {
-            if (contextualType.TypeName == "Task`1")
-            {
-                contextualType = contextualType.OriginalGenericArguments[0];
-            }
-            else if (contextualType.TypeName == "JsonResult`1")
-            {
-                contextualType = contextualType.OriginalGenericArguments[0];
-            }
-            else if (contextualType.TypeName == "ActionResult`1")
-            {
-                contextualType = contextualType.OriginalGenericArguments[0];
-            }
+            GenericResultWrapperTypes.RemoveGenericWrapperTypes (ref contextualType,t=>t.TypeName,t=>t.OriginalGenericArguments[0]);
 
             if (IsFileResponse(contextualType))
             {

src/NSwag.Generation/Processors/OperationResponseProcessorBase.cs

@@ -268,10 +268,7 @@ private void LoadDefaultSuccessResponse(ParameterInfo returnParameter, string su
                 returnType = typeof(void);
             }
 
-            while (returnType.Name == "Task`1" || returnType.Name == "ActionResult`1")
-            {
-                returnType = returnType.GenericTypeArguments[0];
-            }
+            GenericResultWrapperTypes.RemoveGenericWrapperTypes (ref returnType,t=>t.Name,t=>t.GenericTypeArguments[0]);
 
             if (IsVoidResponse(returnType))
             {