Add IParameterTransformer (#750)

src/Microsoft.AspNetCore.Routing.Abstractions/IParameterTransformer.cs

@@ -0,0 +1,18 @@
+// 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 Microsoft.AspNetCore.Routing
+{
+    /// <summary>
+    /// Defines the contract that a class must implement to transform parameter values.
+    /// </summary>
+    public interface IParameterTransformer : IParameterPolicy
+    {
+        /// <summary>
+        /// Transforms the specified parameter value.
+        /// </summary>
+        /// <param name="value">The parameter value to transform.</param>
+        /// <returns>The transformed value.</returns>
+        string Transform(string value);
+    }
+}

src/Microsoft.AspNetCore.Routing/Constraints/NullRouteConstraint.cs

@@ -0,0 +1,21 @@
+// 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.Http;
+
+namespace Microsoft.AspNetCore.Routing.Constraints
+{
+    internal class NullRouteConstraint : IRouteConstraint
+    {
+        public static readonly NullRouteConstraint Instance = new NullRouteConstraint();
+
+        private NullRouteConstraint()
+        {
+        }
+
+        public bool Match(HttpContext httpContext, IRouter route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
+        {
+            return true;
+        }
+    }
+}

src/Microsoft.AspNetCore.Routing/Constraints/StringRouteConstraint.cs

@@ -8,7 +8,7 @@ using Microsoft.AspNetCore.Http;
 namespace Microsoft.AspNetCore.Routing.Constraints
 {
     /// <summary>
-    /// Constrains a route parameter to contain only a specified strign.
+    /// Constrains a route parameter to contain only a specified string.
     /// </summary>
     public class StringRouteConstraint : IRouteConstraint
     {

src/Microsoft.AspNetCore.Routing/DefaultInlineConstraintResolver.cs

@@ -56,7 +56,12 @@ namespace Microsoft.AspNetCore.Routing
                 throw new ArgumentNullException(nameof(inlineConstraint));
             }
 
-            return ParameterPolicyActivator.ResolveParameterPolicy<IRouteConstraint>(_inlineConstraintMap, _serviceProvider, inlineConstraint, out _);
+            // This will return null if the text resolves to a non-IRouteConstraint
+            return ParameterPolicyActivator.ResolveParameterPolicy<IRouteConstraint>(
+                _inlineConstraintMap,
+                _serviceProvider,
+                inlineConstraint,
+                out _);
         }
     }
 }

src/Microsoft.AspNetCore.Routing/DefaultLinkGenerator.cs

@@ -271,7 +271,8 @@ namespace Microsoft.AspNetCore.Routing
                 UrlEncoder.Default,
                 _uriBuildingContextPool,
                 endpoint.RoutePattern,
-                new RouteValueDictionary(endpoint.RoutePattern.Defaults));
+                new RouteValueDictionary(endpoint.RoutePattern.Defaults),
+				_parameterPolicyFactory);
 
             var routeValuesAddressMetadata = endpoint.Metadata.GetMetadata<IRouteValuesAddressMetadata>();
             var templateValuesResult = templateBinder.GetValues(

src/Microsoft.AspNetCore.Routing/DefaultParameterPolicyFactory.cs

@@ -44,7 +44,12 @@ namespace Microsoft.AspNetCore.Routing
                 throw new ArgumentNullException(nameof(inlineText));
             }
 
-            var parameterPolicy = ParameterPolicyActivator.ResolveParameterPolicy<IParameterPolicy>(_options.ConstraintMap, _serviceProvider, inlineText, out var parameterPolicyKey);
+            var parameterPolicy = ParameterPolicyActivator.ResolveParameterPolicy<IParameterPolicy>(
+                _options.ConstraintMap,
+                _serviceProvider,
+                inlineText,
+                out var parameterPolicyKey);
+
             if (parameterPolicy == null)
             {
                 throw new InvalidOperationException(Resources.FormatRoutePattern_ConstraintReferenceNotFound(

src/Microsoft.AspNetCore.Routing/Internal/ParameterPolicyActivator.cs

@@ -13,7 +13,11 @@ namespace Microsoft.AspNetCore.Routing.Internal
 {
     internal static class ParameterPolicyActivator
     {
-        public static T ResolveParameterPolicy<T>(IDictionary<string, Type> inlineParameterPolicyMap, IServiceProvider serviceProvider, string inlineParameterPolicy, out string parameterPolicyKey)
+        public static T ResolveParameterPolicy<T>(
+            IDictionary<string, Type> inlineParameterPolicyMap,
+            IServiceProvider serviceProvider,
+            string inlineParameterPolicy,
+            out string parameterPolicyKey)
             where T : IParameterPolicy
         {
             // IServiceProvider could be null
@@ -51,9 +55,18 @@ namespace Microsoft.AspNetCore.Routing.Internal
 
             if (!typeof(T).IsAssignableFrom(parameterPolicyType))
             {
-                throw new RouteCreationException(
+                if (!typeof(IParameterPolicy).IsAssignableFrom(parameterPolicyType))
-                            Resources.FormatDefaultInlineConstraintResolver_TypeNotConstraint(
+                {
-                                                        parameterPolicyType, parameterPolicyKey, typeof(T).Name));
+                    // Error if type is not a parameter policy
+                    throw new RouteCreationException(
+                                Resources.FormatDefaultInlineConstraintResolver_TypeNotConstraint(
+                                                            parameterPolicyType, parameterPolicyKey, typeof(T).Name));
+                }
+
+                // Return null if type is parameter policy but is not the exact type
+                // This is used by IInlineConstraintResolver for backwards compatibility
+                // e.g. looking for an IRouteConstraint but get a different IParameterPolicy type
+                return default;
             }
 
             try

src/Microsoft.AspNetCore.Routing/Internal/UriBuildingContext.cs

@@ -56,10 +56,10 @@ namespace Microsoft.AspNetCore.Routing.Internal
 
         public bool Accept(string value)
         {
-            return Accept(value, encodeSlashes: true);
+            return Accept(value, encodeSlashes: true, parameterTransformer: null);
         }
 
-        public bool Accept(string value, bool encodeSlashes)
+        public bool Accept(string value, bool encodeSlashes, IParameterTransformer parameterTransformer)
         {
             if (string.IsNullOrEmpty(value))
             {
@@ -117,11 +117,11 @@ namespace Microsoft.AspNetCore.Routing.Internal
             if (_path.Length == 0 && value.Length > 0 && value[0] == '/')
             {
                 _path.Append("/");
-                EncodeValue(value, 1, value.Length - 1, encodeSlashes);
+                EncodeValue(value, 1, value.Length - 1, encodeSlashes, parameterTransformer);
             }
             else
             {
-                EncodeValue(value, encodeSlashes);
+                EncodeValue(value, encodeSlashes, parameterTransformer);
             }
 
             return true;
@@ -263,17 +263,24 @@ namespace Microsoft.AspNetCore.Routing.Internal
 
         private void EncodeValue(string value)
         {
-            EncodeValue(value, encodeSlashes: true);
+            EncodeValue(value, encodeSlashes: true, parameterTransformer: null);
         }
 
-        private void EncodeValue(string value, bool encodeSlashes)
+        private void EncodeValue(string value, bool encodeSlashes, IParameterTransformer parameterTransformer)
         {
-            EncodeValue(value, start: 0, characterCount: value.Length, encodeSlashes);
+            EncodeValue(value, start: 0, characterCount: value.Length, encodeSlashes, parameterTransformer);
         }
 
         // For testing
-        internal void EncodeValue(string value, int start, int characterCount, bool encodeSlashes)
+        internal void EncodeValue(string value, int start, int characterCount, bool encodeSlashes, IParameterTransformer parameterTransformer)
         {
+            if (parameterTransformer != null)
+            {
+                value = parameterTransformer.Transform(value.Substring(0, characterCount));
+                start = 0;
+                characterCount = value.Length;
+            }
+
             // Just encode everything if its ok to encode slashes
             if (encodeSlashes)
             {

src/Microsoft.AspNetCore.Routing/MapRouteRouteBuilderExtensions.cs

@@ -3,6 +3,7 @@
 
 using System;
 using Microsoft.AspNetCore.Routing;
+using Microsoft.AspNetCore.Routing.Constraints;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.AspNetCore.Builder
@@ -107,10 +108,6 @@ namespace Microsoft.AspNetCore.Builder
                 throw new RouteCreationException(Resources.FormatDefaultHandler_MustBeSet(nameof(IRouteBuilder)));
             }
 
-            var inlineConstraintResolver = routeBuilder
-                .ServiceProvider
-                .GetRequiredService<IInlineConstraintResolver>();
-
             routeBuilder.Routes.Add(new Route(
                 routeBuilder.DefaultHandler,
                 name,
@@ -118,9 +115,52 @@ namespace Microsoft.AspNetCore.Builder
                 new RouteValueDictionary(defaults),
                 new RouteValueDictionary(constraints),
                 new RouteValueDictionary(dataTokens),
-                inlineConstraintResolver));
+                CreateInlineConstraintResolver(routeBuilder.ServiceProvider)));
 
             return routeBuilder;
         }
+
+        private static IInlineConstraintResolver CreateInlineConstraintResolver(IServiceProvider serviceProvider)
+        {
+            var inlineConstraintResolver = serviceProvider
+                .GetRequiredService<IInlineConstraintResolver>();
+
+            var parameterPolicyFactory = serviceProvider
+                .GetRequiredService<ParameterPolicyFactory>();
+
+            // This inline constraint resolver will return a null constraint for non-IRouteConstraint
+            // parameter policies so Route does not error
+            return new BackCompatInlineConstraintResolver(inlineConstraintResolver, parameterPolicyFactory);
+        }
+
+        private class BackCompatInlineConstraintResolver : IInlineConstraintResolver
+        {
+            private readonly IInlineConstraintResolver _inner;
+            private readonly ParameterPolicyFactory _parameterPolicyFactory;
+
+            public BackCompatInlineConstraintResolver(IInlineConstraintResolver inner, ParameterPolicyFactory parameterPolicyFactory)
+            {
+                _inner = inner;
+                _parameterPolicyFactory = parameterPolicyFactory;
+            }
+
+            public IRouteConstraint ResolveConstraint(string inlineConstraint)
+            {
+                var routeConstraint = _inner.ResolveConstraint(inlineConstraint);
+                if (routeConstraint != null)
+                {
+                    return routeConstraint;
+                }
+
+                var parameterPolicy = _parameterPolicyFactory.Create(null, inlineConstraint);
+                if (parameterPolicy != null)
+                {
+                    // Logic inside Route will skip adding NullRouteConstraint
+                    return NullRouteConstraint.Instance;
+                }
+
+                return null;
+            }
+        }
     }
 }

src/Microsoft.AspNetCore.Routing/RouteConstraintBuilder.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using Microsoft.AspNetCore.Routing.Constraints;
+using Microsoft.AspNetCore.Routing.Internal;
 
 namespace Microsoft.AspNetCore.Routing
 {
@@ -158,6 +159,11 @@ namespace Microsoft.AspNetCore.Routing
                         _displayName,
                         _inlineConstraintResolver.GetType().Name));
             }
+            else if (constraint == NullRouteConstraint.Instance)
+            {
+                // A null route constraint can be returned for other parameter policy types
+                return;
+            }
 
             Add(key, constraint);
         }

src/Microsoft.AspNetCore.Routing/Template/TemplateBinder.cs

@@ -20,6 +20,7 @@ namespace Microsoft.AspNetCore.Routing.Template
         private readonly ObjectPool<UriBuildingContext> _pool;
 
         private readonly RouteValueDictionary _defaults;
+        private readonly ParameterPolicyFactory _parameterPolicyFactory;
         private readonly RouteValueDictionary _filters;
         private readonly RoutePattern _pattern;
 
@@ -35,7 +36,7 @@ namespace Microsoft.AspNetCore.Routing.Template
             ObjectPool<UriBuildingContext> pool,
             RouteTemplate template,
             RouteValueDictionary defaults)
-            : this(urlEncoder, pool, template?.ToRoutePattern(), defaults)
+            : this(urlEncoder, pool, template?.ToRoutePattern(), defaults, parameterPolicyFactory: null)
         {
         }
 
@@ -46,11 +47,13 @@ namespace Microsoft.AspNetCore.Routing.Template
         /// <param name="pool">The <see cref="ObjectPool{T}"/>.</param>
         /// <param name="pattern">The <see cref="RoutePattern"/> to bind values to.</param>
         /// <param name="defaults">The default values for <paramref name="pattern"/>.</param>
+        /// <param name="parameterPolicyFactory">The <see cref="ParameterPolicyFactory"/>.</param>
         public TemplateBinder(
             UrlEncoder urlEncoder,
             ObjectPool<UriBuildingContext> pool,
             RoutePattern pattern,
-            RouteValueDictionary defaults)
+            RouteValueDictionary defaults,
+            ParameterPolicyFactory parameterPolicyFactory)
         {
             if (urlEncoder == null)
             {
@@ -71,6 +74,7 @@ namespace Microsoft.AspNetCore.Routing.Template
             _pool = pool;
             _pattern = pattern;
             _defaults = defaults;
+            _parameterPolicyFactory = parameterPolicyFactory;
 
             // Any default that doesn't have a corresponding parameter is a 'filter' and if a value
             // is provided for that 'filter' it must match the value in defaults.
@@ -265,7 +269,7 @@ namespace Microsoft.AspNetCore.Routing.Template
                             // Example: template = {id}.{format?}. parameters: id=5
                             // In this case after we have generated "5.", we wont find any value 
                             // for format, so we remove '.' and generate 5.
-                            if (!context.Accept(converted, parameterPart.EncodeSlashes))
+                            if (!context.Accept(converted, parameterPart.EncodeSlashes, GetParameterTransformer(parameterPart)))
                             {
                                 if (j != 0 && parameterPart.IsOptional && (separatorPart = segment.Parts[j - 1] as RoutePatternSeparatorPart) != null)
                                 {
@@ -310,6 +314,26 @@ namespace Microsoft.AspNetCore.Routing.Template
             return true;
         }
 
+        private IParameterTransformer GetParameterTransformer(RoutePatternParameterPart parameterPart)
+        {
+            if (_parameterPolicyFactory == null)
+            {
+                return null;
+            }
+
+            for (var i = 0; i < parameterPart.ParameterPolicies.Count; i++)
+            {
+                // Use the first parameter transformer
+                var parameterPolicy = _parameterPolicyFactory.Create(parameterPart, parameterPart.ParameterPolicies[i]);
+                if (parameterPolicy is IParameterTransformer parameterTransformer)
+                {
+                    return parameterTransformer;
+                }
+            }
+
+            return null;
+        }
+
         private bool AddQueryKeyValueToContext(UriBuildingContext context, string key, object value, bool wroteFirst)
         {
             var converted = Convert.ToString(value, CultureInfo.InvariantCulture);

test/Microsoft.AspNetCore.Routing.Tests/DefaultLinkGeneratorTest.cs

@@ -253,6 +253,35 @@ namespace Microsoft.AspNetCore.Routing
             Assert.Equal("/Foo/Bar%3Fencodeme%3F/Home/In%3Fdex?query=some%3Fquery#Fragment?", path);
         }
 
+        private class UpperCaseParameterTransform : IParameterTransformer
+        {
+            public string Transform(string value)
+            {
+                return value?.ToUpperInvariant();
+            }
+        }
+
+        [Fact]
+        public void GetLink_ParameterTransformer()
+        {
+            // Arrange
+            var endpoint = EndpointFactory.CreateRouteEndpoint("{controller:upper-case}/{name}");
+
+            var routeOptions = new RouteOptions();
+            routeOptions.ConstraintMap["upper-case"] = typeof(UpperCaseParameterTransform);
+
+            var services = GetBasicServices();
+            services.AddSingleton(typeof(UpperCaseParameterTransform), new UpperCaseParameterTransform());
+
+            var linkGenerator = CreateLinkGenerator(routeOptions, services, endpoint);
+
+            // Act
+            var link = linkGenerator.GetPathByRouteValues(routeName: null, new { controller = "Home", name = "Test" });
+
+            // Assert
+            Assert.Equal("/HOME/Test", link);
+        }
+
         // Includes characters that need to be encoded
         [Fact]
         public void GetPathByAddress_WithHttpContext_WithPathBaseAndFragment()

test/Microsoft.AspNetCore.Routing.Tests/Internal/UriBuildingContextTest.cs

@@ -18,7 +18,7 @@ namespace Microsoft.AspNetCore.Routing.Internal
             var uriBuilldingContext = new UriBuildingContext(urlTestEncoder);
             
             // Act
-            uriBuilldingContext.EncodeValue(value, 0, value.Length, encodeSlashes: true);
+            uriBuilldingContext.EncodeValue(value, 0, value.Length, encodeSlashes: true, parameterTransformer: null);
 
             // Assert
             Assert.Equal(expected, uriBuilldingContext.ToString());
@@ -34,7 +34,7 @@ namespace Microsoft.AspNetCore.Routing.Internal
             var uriBuilldingContext = new UriBuildingContext(urlTestEncoder);
 
             // Act
-            uriBuilldingContext.EncodeValue(value, 0, value.Length, encodeSlashes: false);
+            uriBuilldingContext.EncodeValue(value, 0, value.Length, encodeSlashes: false, parameterTransformer: null);
 
             // Assert
             Assert.Equal(expected, uriBuilldingContext.ToString());
@@ -60,7 +60,7 @@ namespace Microsoft.AspNetCore.Routing.Internal
             var uriBuilldingContext = new UriBuildingContext(urlTestEncoder);
 
             // Act
-            uriBuilldingContext.EncodeValue(value, startIndex, characterCount, encodeSlashes: false);
+            uriBuilldingContext.EncodeValue(value, startIndex, characterCount, encodeSlashes: false, parameterTransformer: null);
 
             // Assert
             Assert.Equal(expected, uriBuilldingContext.ToString());

test/Microsoft.AspNetCore.Routing.Tests/LinkGeneratorTestBase.cs

@@ -27,7 +27,7 @@ namespace Microsoft.AspNetCore.Routing
             return httpContext;
         }
 
-        private ServiceCollection GetBasicServices()
+        protected ServiceCollection GetBasicServices()
         {
             var services = new ServiceCollection();
             services.AddSingleton<ObjectPoolProvider, DefaultObjectPoolProvider>();

test/Microsoft.AspNetCore.Routing.Tests/RouteTest.cs

@@ -1582,7 +1582,6 @@ namespace Microsoft.AspNetCore.Routing
             // Assert
             var templateRoute = (Route)routeBuilder.Routes[0];
 
-            // Assert
             Assert.Equal(expectedDictionary.Count, templateRoute.DataTokens.Count);
             foreach (var expectedKey in expectedDictionary.Keys)
             {
@@ -1591,6 +1590,22 @@ namespace Microsoft.AspNetCore.Routing
             }
         }
 
+        [Fact]
+        public void RegisteringRoute_WithParameterPolicy_AbleToAddTheRoute()
+        {
+            // Arrange
+            var routeBuilder = CreateRouteBuilder();
+
+            // Act
+            routeBuilder.MapRoute("mockName",
+                                  "{controller:test-policy}/{action}");
+
+            // Assert
+            var templateRoute = (Route)routeBuilder.Routes[0];
+
+            Assert.Empty(templateRoute.Constraints);
+        }
+
         [Fact]
         public void RegisteringRouteWithInvalidConstraints_Throws()
         {
@@ -1752,6 +1767,8 @@ namespace Microsoft.AspNetCore.Routing
             var services = new ServiceCollection();
             services.AddSingleton<IInlineConstraintResolver>(_inlineConstraintResolver);
             services.AddSingleton<RoutingMarkerService>();
+            services.AddSingleton<ParameterPolicyFactory, DefaultParameterPolicyFactory>();
+            services.Configure<RouteOptions>(ConfigureRouteOptions);
 
             var applicationBuilder = Mock.Of<IApplicationBuilder>();
             applicationBuilder.ApplicationServices = services.BuildServiceProvider();
@@ -1837,12 +1854,24 @@ namespace Microsoft.AspNetCore.Routing
 
         private static IInlineConstraintResolver GetInlineConstraintResolver()
         {
-            var routeOptions = new Mock<IOptions<RouteOptions>>();
+            var routeOptions = new RouteOptions();
-            routeOptions
+            ConfigureRouteOptions(routeOptions);
-                .SetupGet(o => o.Value)
-                .Returns(new RouteOptions());
 
-            return new DefaultInlineConstraintResolver(routeOptions.Object, new TestServiceProvider());
+            var routeOptionsMock = new Mock<IOptions<RouteOptions>>();
+            routeOptionsMock
+                .SetupGet(o => o.Value)
+                .Returns(routeOptions);
+
+            return new DefaultInlineConstraintResolver(routeOptionsMock.Object, new TestServiceProvider());
+        }
+
+        private static void ConfigureRouteOptions(RouteOptions options)
+        {
+            options.ConstraintMap["test-policy"] = typeof(TestPolicy);
+        }
+
+        private class TestPolicy : IParameterPolicy
+        {
         }
     }
 }

test/Microsoft.AspNetCore.Routing.Tests/Template/TemplateBinderTests.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Text.Encodings.Web;
 using Microsoft.AspNetCore.Routing.Internal;
+using Microsoft.AspNetCore.Routing.Patterns;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.ObjectPool;
 using Microsoft.Extensions.Options;
@@ -1288,6 +1289,43 @@ namespace Microsoft.AspNetCore.Routing.Template.Tests
             Assert.Equal(expected, boundTemplate);
         }
 
+        [Fact]
+        public void BindValues_ParameterTransformer()
+        {
+            // Arrange
+            var routeOptions = new RouteOptions();
+            routeOptions.ConstraintMap["test-transformer"] = typeof(TestParameterTransformer);
+            var parameterPolicyFactory = new DefaultParameterPolicyFactory(
+                Options.Create(routeOptions),
+                new ServiceCollection().BuildServiceProvider());
+            var expected = "/ConventionalTansformerRoute/_ConventionalTansformer_/Param/_value_";
+            var template = "ConventionalTansformerRoute/_ConventionalTansformer_/Param/{param:length(500):test-transformer?}";
+            var defaults = new RouteValueDictionary(new { controller = "ConventionalTansformer", action = "Param" });
+            var ambientValues = new RouteValueDictionary(new { controller = "ConventionalTansformer", action = "Param" });
+            var explicitValues = new RouteValueDictionary(new { controller = "ConventionalTansformer", action = "Param", param = "value" });
+            var binder = new TemplateBinder(
+                UrlEncoder.Default,
+                new DefaultObjectPoolProvider().Create(new UriBuilderContextPooledObjectPolicy()),
+                RoutePatternFactory.Parse(template),
+                defaults,
+                parameterPolicyFactory);
+
+            // Act
+            var result = binder.GetValues(ambientValues, explicitValues);
+            var boundTemplate = binder.BindValues(result.AcceptedValues);
+
+            // Assert
+            Assert.Equal(expected, boundTemplate);
+        }
+
+        private class TestParameterTransformer : IParameterTransformer
+        {
+            public string Transform(string value)
+            {
+                return "_" + value + "_";
+            }
+        }
+
         private static IInlineConstraintResolver GetInlineConstraintResolver()
         {
             var services = new ServiceCollection().AddOptions();

test/Microsoft.AspNetCore.Routing.Tests/TemplateParserDefaultValuesTests.cs

@@ -132,6 +132,8 @@ namespace Microsoft.AspNetCore.Routing.Tests
             var services = new ServiceCollection();
             services.AddSingleton<IInlineConstraintResolver>(_inlineConstraintResolver);
             services.AddSingleton<RoutingMarkerService>();
+            services.AddSingleton<ParameterPolicyFactory, DefaultParameterPolicyFactory>();
+            services.Configure<RouteOptions>(options => { });
 
             var applicationBuilder = Mock.Of<IApplicationBuilder>();
             applicationBuilder.ApplicationServices = services.BuildServiceProvider();