[Fixes #3732] Simplify controller discovery.

* Introduce ControllerAttribute and use it to mark base classes as controllers.
* Changed rules for controller discovery to:
  * All controller types must be public, concrete, non open generic types.
  * NotController attribute is not applied to any type oif the hierarchy.
  * The type name ends with controller.
  * Controller attribute is applied to the type or to one of its ancestors.

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

@@ -0,0 +1,17 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.AspNetCore.Mvc
+{
+    /// <summary>
+    /// Indicates that the type and any derived types that this attribute is applied to
+    /// are considered a controller by the default controller discovery mechanism, unless
+    /// <see cref="NonControllerAttribute"/> is applied to any type in the hierarchy.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
+    public class ControllerAttribute : Attribute
+    {
+    }
+}

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

@@ -23,6 +23,7 @@ namespace Microsoft.AspNetCore.Mvc
     /// <summary>
     /// A base class for an MVC controller without view support.
     /// </summary>
+    [Controller]
     public abstract class ControllerBase
     {
         private ControllerContext _controllerContext;

src/Microsoft.AspNetCore.Mvc.Core/Controllers/DefaultControllerTypeProvider.cs

@@ -36,7 +36,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             {
                 var candidateAssemblies = new HashSet<Assembly>(_assemblyProvider.CandidateAssemblies);
                 var types = candidateAssemblies.SelectMany(a => a.DefinedTypes);
-                return types.Where(typeInfo => IsController(typeInfo, candidateAssemblies));
+                return types.Where(typeInfo => IsController(typeInfo));
             }
         }
 
@@ -44,79 +44,48 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
         /// Returns <c>true</c> if the <paramref name="typeInfo"/> is a controller. Otherwise <c>false</c>.
         /// </summary>
         /// <param name="typeInfo">The <see cref="TypeInfo"/>.</param>
-        /// <param name="candidateAssemblies">The set of candidate assemblies.</param>
         /// <returns><c>true</c> if the <paramref name="typeInfo"/> is a controller. Otherwise <c>false</c>.</returns>
-        protected internal virtual bool IsController(
+        protected internal virtual bool IsController(TypeInfo typeInfo)
-            TypeInfo typeInfo,
-            ISet<Assembly> candidateAssemblies)
         {
             if (typeInfo == null)
             {
                 throw new ArgumentNullException(nameof(typeInfo));
             }
 
-            if (candidateAssemblies == null)
-            {
-                throw new ArgumentNullException(nameof(candidateAssemblies));
-            }
-
             if (!typeInfo.IsClass)
             {
                 return false;
             }
+
             if (typeInfo.IsAbstract)
             {
                 return false;
             }
+
             // We only consider public top-level classes as controllers. IsPublic returns false for nested
             // classes, regardless of visibility modifiers
             if (!typeInfo.IsPublic)
             {
                 return false;
             }
+
             if (typeInfo.ContainsGenericParameters)
             {
                 return false;
             }
-            if (!typeInfo.Name.EndsWith(ControllerTypeName, StringComparison.OrdinalIgnoreCase) &&
+
-                !DerivesFromController(typeInfo, candidateAssemblies))
+            if (typeInfo.IsDefined(typeof(NonControllerAttribute)))
             {
                 return false;
             }
-            if (typeInfo.IsDefined(typeof(NonControllerAttribute)))
+
+            if (!typeInfo.Name.EndsWith(ControllerTypeName, StringComparison.OrdinalIgnoreCase) &&
+                !typeInfo.IsDefined(typeof(ControllerAttribute)))
             {
                 return false;
             }
 
             return true;
         }
-
-        private bool DerivesFromController(TypeInfo typeInfo, ISet<Assembly> candidateAssemblies)
-        {
-            while (typeInfo != ObjectTypeInfo)
-            {
-                var baseTypeInfo = typeInfo.BaseType.GetTypeInfo();
-
-                // A base type will be treated as a controller if
-                // a) it ends in the term "Controller" and
-                // b) it's assembly is one of the candidate assemblies we're considering. This ensures that the assembly
-                // the base type is declared in references Mvc.
-                if (baseTypeInfo.Name.EndsWith(ControllerTypeName, StringComparison.Ordinal) &&
-                    candidateAssemblies.Contains(baseTypeInfo.Assembly))
-                {
-                    return true;
-                }
-
-                // c). The base type is called 'Controller.
-                if (string.Equals(baseTypeInfo.Name, ControllerTypeName, StringComparison.Ordinal))
-                {
-                    return true;
-                }
-
-                typeInfo = baseTypeInfo;
-            }
-
-            return false;
-        }
     }
 }

src/Microsoft.AspNetCore.Mvc.WebApiCompatShim/ApiController.cs

@@ -21,6 +21,7 @@ namespace System.Web.Http
     [UseWebApiActionConventions]
     [UseWebApiParameterConventions]
     [UseWebApiOverloading]
+    [Controller]
     public abstract class ApiController : IDisposable
     {
         private ControllerContext _controllerContext;

test/Microsoft.AspNetCore.Mvc.Core.Test/Controllers/DefaultControllerTypeProviderTest.cs

@@ -25,7 +25,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.True(isController);
@@ -39,7 +39,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.True(isController);
@@ -53,10 +53,10 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
-            Assert.False(isController);
+            Assert.True(isController);
         }
 
         [Fact]
@@ -67,7 +67,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.False(isController);
@@ -81,7 +81,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.False(isController);
@@ -95,7 +95,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.False(isController);
@@ -109,7 +109,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.False(isController);
@@ -123,7 +123,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.False(isController);
@@ -137,7 +137,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.True(isController);
@@ -151,7 +151,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.False(isController);
@@ -165,7 +165,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.False(isController);
@@ -179,7 +179,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.True(isController);
@@ -193,7 +193,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.True(isController);
@@ -207,7 +207,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.True(isController);
@@ -221,7 +221,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(typeInfo, CandidateAssemblies);
+            var isController = provider.IsController(typeInfo);
 
             // Assert
             Assert.True(isController);
@@ -230,18 +230,31 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
         [Theory]
         [InlineData(typeof(DescendantLevel1))]
         [InlineData(typeof(DescendantLevel2))]
-        public void IsController_ReturnsTrue_IfAncestorTypeNameHasControllerSuffix(Type type)
+        public void IsController_ReturnsTrue_IfAncestorTypeHasControllerAttribute(Type type)
         {
             // Arrange
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(type.GetTypeInfo(), CandidateAssemblies);
+            var isController = provider.IsController(type.GetTypeInfo());
 
             // Assert
             Assert.True(isController);
         }
 
+        [Fact]
+        public void IsController_ReturnsFalse_IfAncestorTypeDoesNotHaveControllerAttribute()
+        {
+            // Arrange
+            var provider = GetControllerTypeProvider();
+
+            // Act
+            var isController = provider.IsController(typeof(NoSuffixNoControllerAttribute).GetTypeInfo());
+
+            // Assert
+            Assert.False(isController);
+        }
+
         [Theory]
         [InlineData(typeof(BaseNonControllerController))]
         [InlineData(typeof(BaseNonControllerControllerChild))]
@@ -249,6 +262,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
         [InlineData(typeof(BasePocoNonControllerControllerChild))]
         [InlineData(typeof(NonController))]
         [InlineData(typeof(NonControllerChild))]
+        [InlineData(typeof(BaseNonControllerAttributeChildControllerControllerAttributeController))]
         [InlineData(typeof(PersonModel))] // Verifies that POCO type hierarchies that don't derive from controller return false.
         public void IsController_ReturnsFalse_IfTypeOrAncestorHasNonControllerAttribute(Type type)
         {
@@ -256,7 +270,7 @@ namespace Microsoft.AspNetCore.Mvc.Controllers
             var provider = GetControllerTypeProvider();
 
             // Act
-            var isController = provider.IsController(type.GetTypeInfo(), CandidateAssemblies);
+            var isController = provider.IsController(type.GetTypeInfo());
 
             // Assert
             Assert.False(isController);
@@ -297,11 +311,19 @@ namespace Microsoft.AspNetCore.Mvc.DefaultControllerTypeProviderControllers
     {
     }
 
-
+    [Controller]
     public abstract class Controller
     {
     }
 
+    public abstract class NoControllerAttributeBaseController
+    {
+    }
+
+    public class NoSuffixNoControllerAttribute : NoControllerAttributeBaseController
+    {
+    }
+
     public class OpenGenericController<T> : Controller
     {
     }
@@ -327,17 +349,19 @@ namespace Microsoft.AspNetCore.Mvc.DefaultControllerTypeProviderControllers
     {
     }
 
-    public class CustomBaseController
+    [Controller]
+    public class CustomBase
     {
 
     }
 
+    [Controller]
     public abstract class CustomAbstractBaseController
     {
 
     }
 
-    public class DescendantLevel1 : CustomBaseController
+    public class DescendantLevel1 : CustomBase
     {
 
     }
@@ -369,6 +393,12 @@ namespace Microsoft.AspNetCore.Mvc.DefaultControllerTypeProviderControllers
 
     }
 
+    [Controller]
+    public class BaseNonControllerAttributeChildControllerControllerAttributeController : BaseNonControllerController
+    {
+
+    }
+
     public class BaseNonControllerControllerChild : BaseNonControllerController
     {
 

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

@@ -331,16 +331,6 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             Assert.Equal("This is a basic website.", responseData);
         }
 
-        [Fact]
-        public async Task TypesWithoutControllerSuffix_DerivingFromTypesWithControllerSuffix_CanBeAccessed()
-        {
-            // Act
-            var response = await Client.GetStringAsync("appointments");
-
-            // Assert
-            Assert.Equal("2 appointments available.", response);
-        }
-
         [Fact]
         public async Task TypesMarkedAsNonAction_AreInaccessible()
         {

test/Microsoft.AspNetCore.Mvc.FunctionalTests/ControllerFromServicesTests.cs

@@ -47,7 +47,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
         }
 
         [Fact]
-        public async Task TypesDerivingFromControllerPrefixedTypesAreRegistered()
+        public async Task TypesDerivingFromTypesWithControllerAttributeAreRegistered()
         {
             // Arrange
             var expected = "4";

test/Microsoft.AspNetCore.Mvc.WebApiCompatShimTest/ApiControllerActionDiscoveryTest.cs

@@ -55,9 +55,9 @@ namespace System.Web.Http
 
             // Assert
             var controllerType = typeof(TestControllers.Blog).GetTypeInfo();
-            var actions = results.Where(ad => ad.ControllerTypeInfo == controllerType).ToArray();
+            var actions = results.Where(ad => ad.ControllerTypeInfo == controllerType);
 
-            Assert.Empty(actions);
+            Assert.Equal(2, actions.Count());
         }
 
         [Fact]

test/WebSites/BasicWebSite/Controllers/ApplicationBaseController.cs

@@ -1,10 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-namespace BasicWebSite.Controllers
-{
-    public abstract class ApplicationBaseController
-    {
-
-    }
-}

test/WebSites/BasicWebSite/Controllers/Appointments.cs

@@ -1,20 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using Microsoft.AspNetCore.Mvc;
-
-namespace BasicWebSite.Controllers
-{
-    [Route("/appointments")]
-    public class Appointments : ApplicationBaseController
-    {
-        [HttpGet("")]
-        public IActionResult Get()
-        {
-            return new ContentResult
-            {
-                Content = "2 appointments available."
-            };
-        }
-    }
-}

test/WebSites/ControllersFromServicesClassLibrary/ResourcesController.cs

@@ -5,6 +5,7 @@ using Microsoft.AspNetCore.Mvc;
 
 namespace ControllersFromServicesClassLibrary
 {
+    [Controller]
     [Route("/[controller]")]
     public class ResourcesController
     {