Trim Async suffix on action names (#7420)

Fixes https://github.com/aspnet/AspNetCore/issues/4849

src/Mvc/src/Microsoft.AspNetCore.Mvc.Core/ApplicationModels/DefaultApplicationModelProvider.cs

@@ -296,7 +296,7 @@ namespace Microsoft.AspNetCore.Mvc.ApplicationModels
             }
             else
             {
-                actionModel.ActionName = methodInfo.Name;
+                actionModel.ActionName = CanonicalizeActionName(methodInfo.Name);
             }
 
             var apiVisibility = attributes.OfType<IApiDescriptionVisibilityProvider>().FirstOrDefault();
@@ -371,6 +371,19 @@ namespace Microsoft.AspNetCore.Mvc.ApplicationModels
             return actionModel;
         }
 
+        private string CanonicalizeActionName(string actionName)
+        {
+            const string Suffix = "Async";
+
+            if (_mvcOptions.SuppressAsyncSuffixInActionNames &&
+                actionName.EndsWith(Suffix, StringComparison.Ordinal))
+            {
+                actionName = actionName.Substring(0, actionName.Length - Suffix.Length);
+            }
+
+            return actionName;
+        }
+
         /// <summary>
         /// Returns <c>true</c> if the <paramref name="methodInfo"/> is an action. Otherwise <c>false</c>.
         /// </summary>

src/Mvc/src/Microsoft.AspNetCore.Mvc.Core/MvcOptions.cs

@@ -4,7 +4,9 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using Microsoft.AspNetCore.Mvc.Abstractions;
 using Microsoft.AspNetCore.Mvc.ApplicationModels;
+using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.Filters;
 using Microsoft.AspNetCore.Mvc.Formatters;
 using Microsoft.AspNetCore.Mvc.Infrastructure;
@@ -209,6 +211,26 @@ namespace Microsoft.AspNetCore.Mvc
             }
         }
 
+        /// <summary>
+        /// Gets or sets a value that determines if MVC will remove the suffix "Async" applied to
+        /// controller action names.
+        /// <para>
+        /// <see cref="ControllerActionDescriptor.ActionName"/> is used to construct the route to the action as
+        /// well as in view lookup. When <see langword="true"/>, MVC will trim the suffix "Async" applied
+        /// to action method names.
+        /// For example, the action name for <c>ProductsController.ListProductsAsync</c> will be
+        /// canonicalized as <c>ListProducts.</c>. Consequently, it will be routeable at
+        /// <c>/Products/ListProducts</c> with views looked up at <c>/Views/Products/ListProducts.cshtml</c>.
+        /// </para>
+        /// <para>
+        /// This option does not affect values specified using using <see cref="ActionNameAttribute"/>.
+        /// </para>
+        /// </summary>
+        /// <value>
+        /// The default value is <see langword="true"/>.
+        /// </value>
+        public bool SuppressAsyncSuffixInActionNames { get; set; } = true;
+
         IEnumerator<ICompatibilitySwitch> IEnumerable<ICompatibilitySwitch>.GetEnumerator() => _switches.GetEnumerator();
 
         IEnumerator IEnumerable.GetEnumerator() => _switches.GetEnumerator();

src/Mvc/test/Microsoft.AspNetCore.Mvc.Core.Test/ApplicationModels/DefaultApplicationModelProviderTest.cs

@@ -293,6 +293,66 @@ namespace Microsoft.AspNetCore.Mvc.ApplicationModels
                 });
         }
 
+        [Fact]
+        public void OnProvidersExecuting_RemovesAsyncSuffix_WhenOptionIsSet()
+        {
+            // Arrange
+            var options = new MvcOptions();
+            var provider = new TestApplicationModelProvider(options, new EmptyModelMetadataProvider());
+            var typeInfo = typeof(AsyncActionController).GetTypeInfo();
+            var methodInfo = typeInfo.GetMethod(nameof(AsyncActionController.GetPersonAsync));
+
+            var context = new ApplicationModelProviderContext(new[] { typeInfo });
+
+            // Act
+            provider.OnProvidersExecuting(context);
+
+            // Assert
+            var controllerModel = Assert.Single(context.Result.Controllers);
+            var action = Assert.Single(controllerModel.Actions, a => a.ActionMethod == methodInfo);
+            Assert.Equal("GetPerson", action.ActionName);
+        }
+
+        [Fact]
+        public void OnProvidersExecuting_DoesNotRemoveAsyncSuffix_WhenOptionIsDisabled()
+        {
+            // Arrange
+            var options = new MvcOptions { SuppressAsyncSuffixInActionNames = false };
+            var provider = new TestApplicationModelProvider(options, new EmptyModelMetadataProvider());
+            var typeInfo = typeof(AsyncActionController).GetTypeInfo();
+            var methodInfo = typeInfo.GetMethod(nameof(AsyncActionController.GetPersonAsync));
+
+            var context = new ApplicationModelProviderContext(new[] { typeInfo });
+
+            // Act
+            provider.OnProvidersExecuting(context);
+
+            // Assert
+            var controllerModel = Assert.Single(context.Result.Controllers);
+            var action = Assert.Single(controllerModel.Actions, a => a.ActionMethod == methodInfo);
+            Assert.Equal(nameof(AsyncActionController.GetPersonAsync), action.ActionName);
+        }
+
+        [Fact]
+        public void OnProvidersExecuting_DoesNotRemoveAsyncSuffix_WhenActionNameIsSpecifiedUsingActionNameAttribute()
+        {
+            // Arrange
+            var options = new MvcOptions();
+            var provider = new TestApplicationModelProvider(options, new EmptyModelMetadataProvider());
+            var typeInfo = typeof(AsyncActionController).GetTypeInfo();
+            var methodInfo = typeInfo.GetMethod(nameof(AsyncActionController.GetAddressAsync));
+
+            var context = new ApplicationModelProviderContext(new[] { typeInfo });
+
+            // Act
+            provider.OnProvidersExecuting(context);
+
+            // Assert
+            var controllerModel = Assert.Single(context.Result.Controllers);
+            var action = Assert.Single(controllerModel.Actions, a => a.ActionMethod == methodInfo);
+            Assert.Equal("GetRealAddressAsync", action.ActionName);
+        }
+
         [Fact]
         public void CreateControllerModel_DerivedFromControllerClass_HasFilter()
         {
@@ -1774,6 +1834,14 @@ namespace Microsoft.AspNetCore.Mvc.ApplicationModels
             public void Edit() { }
         }
 
+        private class AsyncActionController : Controller
+        {
+            public Task<IActionResult> GetPersonAsync() => null;
+
+            [ActionName("GetRealAddressAsync")]
+            public Task<IActionResult> GetAddressAsync() => null;
+        }
+
         private class TestApplicationModelProvider : DefaultApplicationModelProvider
         {
             public TestApplicationModelProvider()

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ApiExplorerTest.cs

@@ -1398,7 +1398,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
 
             // Act
             var response = await Client.DeleteAsync(
-                $"ApiExplorerResponseTypeWithApiConventionController/DeleteProductAsync");
+                $"ApiExplorerResponseTypeWithApiConventionController/DeleteProduct");
             var responseBody = await response.EnsureSuccessStatusCode().Content.ReadAsStringAsync();
             var result = JsonConvert.DeserializeObject<List<ApiExplorerData>>(responseBody);
 

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/AsyncActionsTests.cs

@@ -278,5 +278,37 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             // Assert
             Assert.Equal("Action exception message: This is a custom exception.", responseBody);
         }
+
+        [Fact]
+        public async Task AsyncSuffixIsIgnored()
+        {
+            // Act
+            var response = await Client.GetAsync("AsyncActions/ActionWithSuffix");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.OK);
+        }
+
+        [Fact]
+        public async Task ActionIsNotRoutedWithAsyncSuffix()
+        {
+            // Act
+            var response = await Client.GetAsync("AsyncActions/ActionWithSuffixAsync");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.NotFound);
+        }
+
+        [Fact]
+        public async Task ViewLookupWithAsyncSuffix()
+        {
+            // Act
+            var response = await Client.GetAsync("AsyncActions/ActionReturningView");
+
+            // Assert
+            await response.AssertStatusCodeAsync(HttpStatusCode.OK);
+            var content = await response.Content.ReadAsStringAsync();
+            Assert.Equal("Hello world!", content.Trim());
+        }
     }
 }

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/BasicTests.cs

@@ -452,7 +452,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         public async Task ActionMethod_ReturningSequenceOfObjectsWrappedInActionResultOfT()
         {
             // Arrange
-            var url = "ActionResultOfT/GetProductsAsync";
+            var url = "ActionResultOfT/GetProducts";
 
             // Act
             var response = await Client.GetStringAsync(url);

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/FlushPointTest.cs

@@ -3,7 +3,6 @@
 
 using System.Net.Http;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Testing.xunit;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc.FunctionalTests
@@ -58,7 +57,7 @@ After flush inside partial<form action=""/FlushPoint/PageWithoutLayout"" method=
 
         [Theory]
         [InlineData("PageWithPartialsAndViewComponents", "FlushAsync invoked inside RenderSection")]
-        [InlineData("PageWithRenderSectionAsync", "FlushAsync invoked inside RenderSectionAsync")]
+        [InlineData("PageWithRenderSection", "FlushAsync invoked inside RenderSectionAsync")]
         public async Task FlushPointsAreExecutedForPagesWithComponentsPartialsAndSections(string action, string title)
         {
             var expected = $@"<title>{ title }</title>

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/ViewEngineTests.cs

@@ -417,7 +417,10 @@ Partial that does not specify Layout
 </layout-for-viewstart-with-layout>";
 
             // Act
-            var body = await Client.GetStringAsync("http://localhost/PartialsWithLayout/PartialsRenderedViaPartialAsync");
+            var response = await Client.GetAsync("http://localhost/PartialsWithLayout/PartialsRenderedViaPartial");
+            await response.AssertStatusCodeAsync(HttpStatusCode.OK);
+
+            var body = await response.Content.ReadAsStringAsync();
 
             // Assert
             Assert.Equal(expected, body.Trim(), ignoreLineEndingDifferences: true);

src/Mvc/test/WebSites/BasicWebSite/Controllers/AsyncActionsController.cs

@@ -26,6 +26,17 @@ namespace BasicWebSite.Controllers
             }
         }
 
+        public async Task<IActionResult> ActionWithSuffixAsync()
+        {
+            await Task.Yield();
+            return Ok();
+        }
+
+        public Task<IActionResult> ActionReturningViewAsync()
+        {
+            return Task.FromResult<IActionResult>(View());
+        }
+
         public async void AsyncVoidAction()
         {
             await Task.Delay(SimulateDelayMilliseconds);

src/Mvc/test/WebSites/BasicWebSite/Views/AsyncActions/ActionReturningView.cshtml

@@ -0,0 +1 @@
+Hello world!

src/Mvc/test/WebSites/RazorWebSite/Controllers/PartialsWithLayoutController.cs

@@ -25,7 +25,7 @@ namespace RazorWebSite.Controllers
         // (b) Partials rendered via PartialAsync can execute Layout.
         public IActionResult PartialsRenderedViaPartialAsync()
         {
-            return View();
+            return View(nameof(PartialsRenderedViaPartialAsync));
         }
     }
 }