MVC reaction to RoutePattern required values

src/Mvc/benchmarks/Microsoft.AspNetCore.Mvc.Performance/MvcEndpointDatasourceBenchmark.cs

@@ -58,6 +58,8 @@ namespace Microsoft.AspNetCore.Mvc.Performance
         {
             var endpointDataSource = CreateMvcEndpointDataSource(_attributeActionProvider);
             var endpoints = endpointDataSource.Endpoints;
+
+            AssertHasEndpoints(endpoints);
         }
 
         [Benchmark]
@@ -66,6 +68,8 @@ namespace Microsoft.AspNetCore.Mvc.Performance
             var endpointDataSource = CreateMvcEndpointDataSource(_conventionalActionProvider);
             endpointDataSource.ConventionalEndpointInfos.AddRange(_conventionalEndpointInfos);
             var endpoints = endpointDataSource.Endpoints;
+
+            AssertHasEndpoints(endpoints);
         }
 
         private ActionDescriptor CreateAttributeRoutedAction(int id)
@@ -110,11 +114,20 @@ namespace Microsoft.AspNetCore.Mvc.Performance
             var dataSource = new MvcEndpointDataSource(
                 actionDescriptorCollectionProvider,
                 new MvcEndpointInvokerFactory(new ActionInvokerFactory(Array.Empty<IActionInvokerProvider>())),
-                new MockParameterPolicyFactory());
+                new MockParameterPolicyFactory(),
+                new MockRoutePatternTransformer());
 
             return dataSource;
         }
 
+        private class MockRoutePatternTransformer : RoutePatternTransformer
+        {
+            public override RoutePattern SubstituteRequiredValues(RoutePattern original, object requiredValues)
+            {
+                return original;
+            }
+        }
+
         private class MockActionDescriptorCollectionProvider : IActionDescriptorCollectionProvider
         {
             public MockActionDescriptorCollectionProvider(List<ActionDescriptor> actionDescriptors)
@@ -137,5 +150,13 @@ namespace Microsoft.AspNetCore.Mvc.Performance
                 throw new NotImplementedException();
             }
         }
+
+        private static void AssertHasEndpoints(IReadOnlyList<Http.Endpoint> endpoints)
+        {
+            if (endpoints.Count == 0)
+            {
+                throw new InvalidOperationException("Expected endpoints from data source.");
+            }
+        }
     }
 }

src/Mvc/samples/MvcSandbox/SlugifyParameterTransformer.cs

@@ -0,0 +1,19 @@
+// 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;
+using System.Text.RegularExpressions;
+using Microsoft.AspNetCore.Routing;
+
+namespace MvcSandbox
+{
+    public class SlugifyParameterTransformer : IOutboundParameterTransformer
+    {
+        public string TransformOutbound(object value)
+        {
+            // Slugify value
+            return value == null ? null : Regex.Replace(value.ToString(), "([a-z])([A-Z])", "$1-$2", RegexOptions.None, TimeSpan.FromMilliseconds(100)).ToLower();
+        }
+    }
+}
+

src/Mvc/samples/MvcSandbox/Startup.cs

@@ -5,11 +5,13 @@ using System;
 using System.IO;
 using System.Linq;
 using System.Text;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Routing;
+using Microsoft.AspNetCore.Routing.Internal;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 
@@ -20,6 +22,10 @@ namespace MvcSandbox
         // This method gets called by the runtime. Use this method to add services to the container.
         public void ConfigureServices(IServiceCollection services)
         {
+            services.AddRouting(options =>
+            {
+                options.ConstraintMap["slugify"] = typeof(SlugifyParameterTransformer);
+            });
             services.AddMvc().SetCompatibilityVersion(Microsoft.AspNetCore.Mvc.CompatibilityVersion.Latest);
         }
 
@@ -37,6 +43,27 @@ namespace MvcSandbox
                     name: "default",
                     template: "{controller=Home}/{action=Index}/{id?}");
 
+                builder.MapControllerRoute(
+                    name: "transform",
+                    template: "Transform/{controller:slugify=Home}/{action:slugify=Index}/{id?}",
+                    defaults: null,
+                    constraints: new { controller = "Home" });
+
+                builder.MapGet(
+                    "/graph",
+                    "DFA Graph",
+                    (httpContext) =>
+                    {
+                        using (var writer = new StreamWriter(httpContext.Response.Body, Encoding.UTF8, 1024, leaveOpen: true))
+                        {
+                            var graphWriter = httpContext.RequestServices.GetRequiredService<DfaGraphWriter>();
+                            var dataSource = httpContext.RequestServices.GetRequiredService<EndpointDataSource>();
+                            graphWriter.Write(dataSource, writer);
+                        }
+
+                        return Task.CompletedTask;
+                    });
+
                 builder.MapApplication();
 
                 builder.MapHealthChecks("/healthz");
@@ -50,7 +77,7 @@ namespace MvcSandbox
 
         private static Task WriteEndpoints(HttpContext httpContext)
         {
-            var dataSource = httpContext.RequestServices.GetRequiredService<CompositeEndpointDataSource>();
+            var dataSource = httpContext.RequestServices.GetRequiredService<EndpointDataSource>();
 
             var sb = new StringBuilder();
             sb.AppendLine("Endpoints:");
@@ -81,6 +108,7 @@ namespace MvcSandbox
                     factory
                         .AddConsole()
                         .AddDebug();
+                    factory.SetMinimumLevel(LogLevel.Trace);
                 })
                 .UseIISIntegration()
                 .UseKestrel()

src/Mvc/src/Microsoft.AspNetCore.Mvc.Core/Routing/MvcEndpointDataSource.cs

@@ -5,13 +5,11 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
-using System.Text;
 using System.Threading;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc.Abstractions;
 using Microsoft.AspNetCore.Mvc.ActionConstraints;
-using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.Filters;
 using Microsoft.AspNetCore.Mvc.Infrastructure;
 using Microsoft.AspNetCore.Routing;
@@ -25,6 +23,7 @@ namespace Microsoft.AspNetCore.Mvc.Routing
         private readonly IActionDescriptorCollectionProvider _actions;
         private readonly MvcEndpointInvokerFactory _invokerFactory;
         private readonly ParameterPolicyFactory _parameterPolicyFactory;
+        private readonly RoutePatternTransformer _routePatternTransformer;
 
         // The following are protected by this lock for WRITES only. This pattern is similar
         // to DefaultActionDescriptorChangeProvider - see comments there for details on
@@ -37,26 +36,13 @@ namespace Microsoft.AspNetCore.Mvc.Routing
         public MvcEndpointDataSource(
             IActionDescriptorCollectionProvider actions,
             MvcEndpointInvokerFactory invokerFactory,
-            ParameterPolicyFactory parameterPolicyFactory)
+            ParameterPolicyFactory parameterPolicyFactory,
+            RoutePatternTransformer routePatternTransformer)
         {
-            if (actions == null)
-            {
-                throw new ArgumentNullException(nameof(actions));
-            }
-
-            if (invokerFactory == null)
-            {
-                throw new ArgumentNullException(nameof(invokerFactory));
-            }
-
-            if (parameterPolicyFactory == null)
-            {
-                throw new ArgumentNullException(nameof(parameterPolicyFactory));
-            }
-
             _actions = actions;
             _invokerFactory = invokerFactory;
             _parameterPolicyFactory = parameterPolicyFactory;
+            _routePatternTransformer = routePatternTransformer;
 
             ConventionalEndpointInfos = new List<MvcEndpointInfo>();
             AttributeRoutingConventionResolvers = new List<Func<ActionDescriptor, DefaultEndpointConventionBuilder>>();
@@ -115,7 +101,6 @@ namespace Microsoft.AspNetCore.Mvc.Routing
             lock (_lock)
             {
                 var endpoints = new List<Endpoint>();
-                StringBuilder patternStringBuilder = null;
 
                 foreach (var action in _actions.ActionDescriptors.Items)
                 {
@@ -129,48 +114,31 @@ namespace Microsoft.AspNetCore.Mvc.Routing
                         // This is for scenarios dealing with migrating existing Router based code to Endpoint Routing world.
                         var conventionalRouteOrder = 1;
 
-                        // Check each of the conventional patterns to see if the action would be reachable
+                        // Check each of the conventional patterns to see if the action would be reachable.
-                        // If the action and pattern are compatible then create an endpoint with the
+                        // If the action and pattern are compatible then create an endpoint with action
-                        // area/controller/action parameter parts replaced with literals
+                        // route values on the pattern.
-                        //
-                        // e.g. {controller}/{action} with HomeController.Index and HomeController.Login
-                        // would result in endpoints:
-                        // - Home/Index
-                        // - Home/Login
                         foreach (var endpointInfo in ConventionalEndpointInfos)
                         {
                             // An 'endpointInfo' is applicable if:
-                            // 1. it has a parameter (or default value) for 'required' non-null route value
+                            // 1. It has a parameter (or default value) for 'required' non-null route value
-                            // 2. it does not have a parameter (or default value) for 'required' null route value
+                            // 2. It does not have a parameter (or default value) for 'required' null route value
-                            var isApplicable = true;
+                            var updatedRoutePattern = _routePatternTransformer.SubstituteRequiredValues(endpointInfo.ParsedPattern, action.RouteValues);
-                            foreach (var routeKey in action.RouteValues.Keys)
-                            {
-                                if (!MatchRouteValue(action, endpointInfo, routeKey))
-                                {
-                                    isApplicable = false;
-                                    break;
-                                }
-                            }
 
-                            if (!isApplicable)
+                            if (updatedRoutePattern == null)
                             {
                                 continue;
                             }
 
-                            conventionalRouteOrder = CreateEndpoints(
+                            var endpoint = CreateEndpoint(
-                                endpoints,
-                                ref patternStringBuilder,
                                 action,
-                                conventionalRouteOrder,
+                                updatedRoutePattern,
-                                endpointInfo.ParsedPattern,
-                                endpointInfo.MergedDefaults,
-                                endpointInfo.Defaults,
                                 endpointInfo.Name,
+                                conventionalRouteOrder++,
                                 endpointInfo.DataTokens,
-                                endpointInfo.ParameterPolicies,
+                                false,
-                                suppressLinkGeneration: false,
+                                false,
-                                suppressPathMatching: false,
                                 endpointInfo.Conventions);
+                            endpoints.Add(endpoint);
                         }
                     }
                     else
@@ -185,20 +153,27 @@ namespace Microsoft.AspNetCore.Mvc.Routing
 
                         var attributeRoutePattern = RoutePatternFactory.Parse(action.AttributeRouteInfo.Template);
 
-                        CreateEndpoints(
+                        // Modify the route and required values to ensure required values can be successfully subsituted.
-                            endpoints,
+                        // Subsitituting required values into an attribute route pattern should always succeed.
-                            ref patternStringBuilder,
+                        var (resolvedRoutePattern, resolvedRouteValues) = ResolveDefaultsAndRequiredValues(action, attributeRoutePattern);
+
+                        var updatedRoutePattern = _routePatternTransformer.SubstituteRequiredValues(resolvedRoutePattern, resolvedRouteValues);
+
+                        if (updatedRoutePattern == null)
+                        {
+                            throw new InvalidOperationException("Failed to update route pattern with required values.");
+                        }
+
+                        var endpoint = CreateEndpoint(
                             action,
-                            action.AttributeRouteInfo.Order,
+                            updatedRoutePattern,
-                            attributeRoutePattern,
-                            attributeRoutePattern.Defaults,
-                            nonInlineDefaults: null,
                             action.AttributeRouteInfo.Name,
+                            action.AttributeRouteInfo.Order,
                             dataTokens: null,
-                            allParameterPolicies: null,
                             action.AttributeRouteInfo.SuppressLinkGeneration,
                             action.AttributeRouteInfo.SuppressPathMatching,
                             conventionBuilder.Conventions);
+                        endpoints.Add(endpoint);
                     }
                 }
 
@@ -220,6 +195,58 @@ namespace Microsoft.AspNetCore.Mvc.Routing
             }
         }
 
+        private static (RoutePattern resolvedRoutePattern, IDictionary<string, string> resolvedRequiredValues) ResolveDefaultsAndRequiredValues(ActionDescriptor action, RoutePattern attributeRoutePattern)
+        {
+            RouteValueDictionary updatedDefaults = null;
+            IDictionary<string, string> resolvedRequiredValues = null;
+
+            foreach (var routeValue in action.RouteValues)
+            {
+                var parameter = attributeRoutePattern.GetParameter(routeValue.Key);
+
+                if (!RouteValueEqualityComparer.Default.Equals(routeValue.Value, string.Empty))
+                {
+                    if (parameter == null)
+                    {
+                        // The attribute route has a required value with no matching parameter
+                        // Add the required values without a parameter as a default
+                        // e.g.
+                        //   Template: "Login/{action}"
+                        //   Required values: { controller = "Login", action = "Index" }
+                        //   Updated defaults: { controller = "Login" }
+
+                        if (updatedDefaults == null)
+                        {
+                            updatedDefaults = new RouteValueDictionary(attributeRoutePattern.Defaults);
+                        }
+
+                        updatedDefaults[routeValue.Key] = routeValue.Value;
+                    }
+                }
+                else
+                {
+                    if (parameter != null)
+                    {
+                        // The attribute route has a null or empty required value with a matching parameter
+                        // Remove the required value from the route
+
+                        if (resolvedRequiredValues == null)
+                        {
+                            resolvedRequiredValues = new Dictionary<string, string>(action.RouteValues);
+                        }
+
+                        resolvedRequiredValues.Remove(parameter.Name);
+                    }
+                }
+            }
+            if (updatedDefaults != null)
+            {
+                attributeRoutePattern = RoutePatternFactory.Parse(action.AttributeRouteInfo.Template, updatedDefaults, parameterPolicies: null);
+            }
+
+            return (attributeRoutePattern, resolvedRequiredValues ?? action.RouteValues);
+        }
+
         private DefaultEndpointConventionBuilder ResolveActionConventionBuilder(ActionDescriptor action)
         {
             foreach (var filter in AttributeRoutingConventionResolvers)
@@ -234,339 +261,10 @@ namespace Microsoft.AspNetCore.Mvc.Routing
             return null;
         }
 
-        // CreateEndpoints processes the route pattern, replacing area/controller/action parameters with endpoint values
-        // Because of default values it is possible for a route pattern to resolve to multiple endpoints
-        private int CreateEndpoints(
-            List<Endpoint> endpoints,
-            ref StringBuilder patternStringBuilder,
-            ActionDescriptor action,
-            int routeOrder,
-            RoutePattern routePattern,
-            IReadOnlyDictionary<string, object> allDefaults,
-            IReadOnlyDictionary<string, object> nonInlineDefaults,
-            string name,
-            RouteValueDictionary dataTokens,
-            IDictionary<string, IList<IParameterPolicy>> allParameterPolicies,
-            bool suppressLinkGeneration,
-            bool suppressPathMatching,
-            List<Action<EndpointModel>> conventions)
-        {
-            var newPathSegments = routePattern.PathSegments.ToList();
-            var hasLinkGenerationEndpoint = false;
-
-            // Create a mutable copy
-            var nonInlineDefaultsCopy = nonInlineDefaults != null
-                ? new RouteValueDictionary(nonInlineDefaults)
-                : null;
-
-            var resolvedRouteValues = ResolveActionRouteValues(action, allDefaults);
-
-            for (var i = 0; i < newPathSegments.Count; i++)
-            {
-                // Check if the pattern can be shortened because the remaining parameters are optional
-                //
-                // e.g. Matching pattern {controller=Home}/{action=Index} against HomeController.Index
-                // can resolve to the following endpoints: (sorted by RouteEndpoint.Order)
-                // - /
-                // - /Home
-                // - /Home/Index
-                if (UseDefaultValuePlusRemainingSegmentsOptional(
-                    i,
-                    action,
-                    resolvedRouteValues,
-                    allDefaults,
-                    ref nonInlineDefaultsCopy,
-                    newPathSegments))
-                {
-                    // The route pattern has matching default values AND an optional parameter
-                    // For link generation we need to include an endpoint with parameters and default values
-                    // so the link is correctly shortened
-                    // e.g. {controller=Home}/{action=Index}/{id=17}
-                    if (!hasLinkGenerationEndpoint)
-                    {
-                        var ep = CreateEndpoint(
-                            action,
-                            resolvedRouteValues,
-                            name,
-                            GetPattern(ref patternStringBuilder, newPathSegments),
-                            newPathSegments,
-                            nonInlineDefaultsCopy,
-                            routeOrder++,
-                            dataTokens,
-                            suppressLinkGeneration,
-                            true,
-                            conventions);
-                        endpoints.Add(ep);
-
-                        hasLinkGenerationEndpoint = true;
-                    }
-
-                    var subPathSegments = newPathSegments.Take(i);
-
-                    var subEndpoint = CreateEndpoint(
-                        action,
-                        resolvedRouteValues,
-                        name,
-                        GetPattern(ref patternStringBuilder, subPathSegments),
-                        subPathSegments,
-                        nonInlineDefaultsCopy,
-                        routeOrder++,
-                        dataTokens,
-                        suppressLinkGeneration,
-                        suppressPathMatching,
-                        conventions);
-                    endpoints.Add(subEndpoint);
-                }
-
-                UpdatePathSegments(i, action, resolvedRouteValues, routePattern, newPathSegments, ref allParameterPolicies);
-            }
-
-            var finalEndpoint = CreateEndpoint(
-                action,
-                resolvedRouteValues,
-                name,
-                GetPattern(ref patternStringBuilder, newPathSegments),
-                newPathSegments,
-                nonInlineDefaultsCopy,
-                routeOrder++,
-                dataTokens,
-                suppressLinkGeneration,
-                suppressPathMatching,
-                conventions);
-            endpoints.Add(finalEndpoint);
-
-            return routeOrder;
-
-            string GetPattern(ref StringBuilder sb, IEnumerable<RoutePatternPathSegment> segments)
-            {
-                if (sb == null)
-                {
-                    sb = new StringBuilder();
-                }
-
-                RoutePatternWriter.WriteString(sb, segments);
-                var rawPattern = sb.ToString();
-                sb.Length = 0;
-
-                return rawPattern;
-            }
-        }
-
-        private static IDictionary<string, string> ResolveActionRouteValues(ActionDescriptor action, IReadOnlyDictionary<string, object> allDefaults)
-        {
-            Dictionary<string, string> resolvedRequiredValues = null;
-
-            foreach (var kvp in action.RouteValues)
-            {
-                // Check whether there is a matching default value with a different case
-                // e.g. {controller=HOME}/{action} with HomeController.Index will have route values:
-                // - controller = HOME
-                // - action = Index
-                if (allDefaults.TryGetValue(kvp.Key, out var value) &&
-                    value is string defaultValue &&
-                    !string.Equals(kvp.Value, defaultValue, StringComparison.Ordinal) &&
-                    string.Equals(kvp.Value, defaultValue, StringComparison.OrdinalIgnoreCase))
-                {
-                    if (resolvedRequiredValues == null)
-                    {
-                        resolvedRequiredValues = new Dictionary<string, string>(action.RouteValues, StringComparer.OrdinalIgnoreCase);
-                    }
-
-                    resolvedRequiredValues[kvp.Key] = defaultValue;
-                }
-            }
-
-            return resolvedRequiredValues ?? action.RouteValues;
-        }
-
-        private void UpdatePathSegments(
-            int i,
-            ActionDescriptor action,
-            IDictionary<string, string> resolvedRequiredValues,
-            RoutePattern routePattern,
-            List<RoutePatternPathSegment> newPathSegments,
-            ref IDictionary<string, IList<IParameterPolicy>> allParameterPolicies)
-        {
-            List<RoutePatternPart> segmentParts = null; // Initialize only as needed
-            var segment = newPathSegments[i];
-            for (var j = 0; j < segment.Parts.Count; j++)
-            {
-                var part = segment.Parts[j];
-
-                if (part is RoutePatternParameterPart parameterPart)
-                {
-                    if (resolvedRequiredValues.TryGetValue(parameterPart.Name, out var parameterRouteValue))
-                    {
-                        if (segmentParts == null)
-                        {
-                            segmentParts = segment.Parts.ToList();
-                        }
-                        if (allParameterPolicies == null)
-                        {
-                            allParameterPolicies = MvcEndpointInfo.BuildParameterPolicies(routePattern.Parameters, _parameterPolicyFactory);
-                        }
-
-                        // Route value could be null if it is a "known" route value.
-                        // Do not use the null value to de-normalize the route pattern,
-                        // instead leave the parameter unchanged.
-                        // e.g.
-                        //     RouteValues will contain a null "page" value if there are Razor pages
-                        //     Skip replacing the {page} parameter
-                        if (parameterRouteValue != null)
-                        {
-                            if (allParameterPolicies.TryGetValue(parameterPart.Name, out var parameterPolicies))
-                            {
-                                // Check if the parameter has a transformer policy
-                                // Use the first transformer policy
-                                for (var k = 0; k < parameterPolicies.Count; k++)
-                                {
-                                    if (parameterPolicies[k] is IOutboundParameterTransformer parameterTransformer)
-                                    {
-                                        parameterRouteValue = parameterTransformer.TransformOutbound(parameterRouteValue);
-                                        break;
-                                    }
-                                }
-                            }
-
-                            segmentParts[j] = RoutePatternFactory.LiteralPart(parameterRouteValue);
-                        }
-                    }
-                }
-            }
-
-            // A parameter part was replaced so replace segment with updated parts
-            if (segmentParts != null)
-            {
-                newPathSegments[i] = RoutePatternFactory.Segment(segmentParts);
-            }
-
-        }
-
-        private bool UseDefaultValuePlusRemainingSegmentsOptional(
-            int segmentIndex,
-            ActionDescriptor action,
-            IDictionary<string, string> resolvedRequiredValues,
-            IReadOnlyDictionary<string, object> allDefaults,
-            ref RouteValueDictionary nonInlineDefaults,
-            List<RoutePatternPathSegment> pathSegments)
-        {
-            // Check whether the remaining segments are all optional and one or more of them is
-            // for area/controller/action and has a default value
-            var usedDefaultValue = false;
-
-            for (var i = segmentIndex; i < pathSegments.Count; i++)
-            {
-                var segment = pathSegments[i];
-                for (var j = 0; j < segment.Parts.Count; j++)
-                {
-                    var part = segment.Parts[j];
-                    if (part.IsParameter && part is RoutePatternParameterPart parameterPart)
-                    {
-                        if (allDefaults.TryGetValue(parameterPart.Name, out var v))
-                        {
-                            if (resolvedRequiredValues.TryGetValue(parameterPart.Name, out var routeValue))
-                            {
-                                if (string.Equals(v as string, routeValue, StringComparison.OrdinalIgnoreCase))
-                                {
-                                    usedDefaultValue = true;
-                                    continue;
-                                }
-                            }
-                            else
-                            {
-                                if (nonInlineDefaults == null)
-                                {
-                                    nonInlineDefaults = new RouteValueDictionary();
-                                }
-                                nonInlineDefaults.TryAdd(parameterPart.Name, v);
-
-                                usedDefaultValue = true;
-                                continue;
-                            }
-                        }
-
-                        if (parameterPart.IsOptional || parameterPart.IsCatchAll)
-                        {
-                            continue;
-                        }
-                    }
-                    else if (part.IsSeparator && part is RoutePatternSeparatorPart separatorPart
-                        && separatorPart.Content == ".")
-                    {
-                        // Check if this pattern ends in an optional extension, e.g. ".{ext?}"
-                        // Current literal must be "." and followed by a single optional parameter part
-                        var nextPartIndex = j + 1;
-
-                        if (nextPartIndex == segment.Parts.Count - 1
-                            && segment.Parts[nextPartIndex].IsParameter
-                            && segment.Parts[nextPartIndex] is RoutePatternParameterPart extensionParameterPart
-                            && extensionParameterPart.IsOptional)
-                        {
-                            continue;
-                        }
-                    }
-
-                    // Stop because there is a non-optional/non-defaulted trailing value
-                    return false;
-                }
-            }
-
-            return usedDefaultValue;
-        }
-
-        private bool MatchRouteValue(ActionDescriptor action, MvcEndpointInfo endpointInfo, string routeKey)
-        {
-            if (!action.RouteValues.TryGetValue(routeKey, out var actionValue) || string.IsNullOrWhiteSpace(actionValue))
-            {
-                // Action does not have a value for this routeKey, most likely because action is not in an area
-                // Check that the pattern does not have a parameter for the routeKey
-                var matchingParameter = endpointInfo.ParsedPattern.GetParameter(routeKey);
-                if (matchingParameter == null &&
-                    (!endpointInfo.ParsedPattern.Defaults.TryGetValue(routeKey, out var value) ||
-                    !string.IsNullOrEmpty(Convert.ToString(value))))
-                {
-                    return true;
-                }
-            }
-            else
-            {
-                if (endpointInfo.MergedDefaults != null && string.Equals(actionValue, endpointInfo.MergedDefaults[routeKey] as string, StringComparison.OrdinalIgnoreCase))
-                {
-                    return true;
-                }
-
-                var matchingParameter = endpointInfo.ParsedPattern.GetParameter(routeKey);
-                if (matchingParameter != null)
-                {
-                    // Check that the value matches against constraints on that parameter
-                    // e.g. For {controller:regex((Home|Login))} the controller value must match the regex
-                    if (endpointInfo.ParameterPolicies.TryGetValue(routeKey, out var parameterPolicies))
-                    {
-                        foreach (var policy in parameterPolicies)
-                        {
-                            if (policy is IRouteConstraint constraint
-                                && !constraint.Match(httpContext: null, NullRouter.Instance, routeKey, new RouteValueDictionary(action.RouteValues), RouteDirection.IncomingRequest))
-                            {
-                                // Did not match constraint
-                                return false;
-                            }
-                        }
-                    }
-
-                    return true;
-                }
-            }
-
-            return false;
-        }
-
         private RouteEndpoint CreateEndpoint(
             ActionDescriptor action,
-            IDictionary<string, string> actionRouteValues,
+            RoutePattern routePattern,
             string routeName,
-            string patternRawText,
-            IEnumerable<RoutePatternPathSegment> segments,
-            object nonInlineDefaults,
             int order,
             RouteValueDictionary dataTokens,
             bool suppressLinkGeneration,
@@ -583,16 +281,12 @@ namespace Microsoft.AspNetCore.Mvc.Routing
                 return invoker.InvokeAsync();
             };
 
-            var defaults = new RouteValueDictionary(nonInlineDefaults);
+            var model = new RouteEndpointModel(requestDelegate, routePattern, order);
-            EnsureRequiredValuesInDefaults(actionRouteValues, defaults, segments);
-
-            var model = new RouteEndpointModel(requestDelegate, RoutePatternFactory.Pattern(patternRawText, defaults, parameterPolicies: null, segments), order);
 
             AddEndpointMetadata(
                 model.Metadata,
                 action,
                 routeName,
-                new RouteValueDictionary(actionRouteValues),
                 dataTokens,
                 suppressLinkGeneration,
                 suppressPathMatching);
@@ -616,7 +310,6 @@ namespace Microsoft.AspNetCore.Mvc.Routing
             IList<object> metadata,
             ActionDescriptor action,
             string routeName,
-            RouteValueDictionary requiredValues,
             RouteValueDictionary dataTokens,
             bool suppressLinkGeneration,
             bool suppressPathMatching)
@@ -637,7 +330,7 @@ namespace Microsoft.AspNetCore.Mvc.Routing
                 metadata.Add(new DataTokensMetadata(dataTokens));
             }
 
-            metadata.Add(new RouteValuesAddressMetadata(routeName, requiredValues));
+            metadata.Add(new RouteNameMetadata(routeName));
 
             // Add filter descriptors to endpoint metadata
             if (action.FilterDescriptors != null && action.FilterDescriptors.Count > 0)
@@ -685,33 +378,5 @@ namespace Microsoft.AspNetCore.Mvc.Routing
                 metadata.Add(new SuppressMatchingMetadata());
             }
         }
-
-        // Ensure route values are a subset of defaults
-        // Examples:
-        //
-        // Template: {controller}/{action}/{category}/{id?}
-        // Defaults(in-line or non in-line): category=products
-        // Required values: controller=foo, action=bar
-        // Final constructed pattern: foo/bar/{category}/{id?}
-        // Final defaults: controller=foo, action=bar, category=products
-        //
-        // Template: {controller=Home}/{action=Index}/{category=products}/{id?}
-        // Defaults: controller=Home, action=Index, category=products
-        // Required values: controller=foo, action=bar
-        // Final constructed pattern: foo/bar/{category}/{id?}
-        // Final defaults: controller=foo, action=bar, category=products
-        private void EnsureRequiredValuesInDefaults(
-            IDictionary<string, string> routeValues,
-            RouteValueDictionary defaults,
-            IEnumerable<RoutePatternPathSegment> segments)
-        {
-            foreach (var kvp in routeValues)
-            {
-                if (kvp.Value != null)
-                {
-                    defaults[kvp.Key] = kvp.Value;
-                }
-            }
-        }
     }
 }

src/Mvc/test/Microsoft.AspNetCore.Mvc.Core.Test/Routing/ControllerLinkGeneratorExtensionsTest.cs

@@ -25,11 +25,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "Home/Index/{id}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
             var endpoint2 = CreateEndpoint(
                 "Home/Index/{id?}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -55,11 +55,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "Home/Index/{id}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
             var endpoint2 = CreateEndpoint(
                 "Home/Index/{id?}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -83,11 +83,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "Home/Index/{id}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
             var endpoint2 = CreateEndpoint(
                 "Home/Index/{id?}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -114,11 +114,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "Home/Index/{id}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
             var endpoint2 = CreateEndpoint(
                 "Home/Index/{id?}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -144,11 +144,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "Home/Index/{id}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
             var endpoint2 = CreateEndpoint(
                 "Home/Index/{id?}",
                 defaults: new { controller = "Home", action = "Index", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { controller = "Home", action = "Index", })) });
+                requiredValues: new { controller = "Home", action = "Index" });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -177,7 +177,7 @@ namespace Microsoft.AspNetCore.Routing
         {
             return new RouteEndpoint(
                 (httpContext) => Task.CompletedTask,
-                RoutePatternFactory.Parse(template, defaults, parameterPolicies: null),
+                RoutePatternFactory.Parse(template, defaults, parameterPolicies: null, requiredValues),
                 order,
                 new EndpointMetadataCollection(metadata ?? Array.Empty<object>()),
                 null);

src/Mvc/test/Microsoft.AspNetCore.Mvc.Core.Test/Routing/EndpointRoutingUrlHelperTest.cs

@@ -114,7 +114,7 @@ namespace Microsoft.AspNetCore.Mvc.Routing
                 "Home/Index",
                 defaults: new { controller = "Home", action = "Index" },
                 requiredValues: new { controller = "Home", action = "Index" },
-                metadataCollection: new EndpointMetadataCollection(new[] { new SuppressLinkGenerationMetadata() }));
+                metadata: new[] { new SuppressLinkGenerationMetadata() });
             var urlHelper = CreateUrlHelper(new[] { endpoint });
 
             // Act
@@ -273,19 +273,20 @@ namespace Microsoft.AspNetCore.Mvc.Routing
             object requiredValues = null,
             int order = 0,
             string routeName = null,
-            EndpointMetadataCollection metadataCollection = null)
+            IList<object> metadata = null)
         {
-            if (metadataCollection == null)
+            metadata = metadata ?? new List<object>();
+
+            if (routeName != null)
             {
-                metadataCollection = new EndpointMetadataCollection(
+                metadata.Add(new RouteNameMetadata(routeName));
-                    new RouteValuesAddressMetadata(routeName, new RouteValueDictionary(requiredValues)));
             }
 
             return new RouteEndpoint(
                 (httpContext) => Task.CompletedTask,
-                RoutePatternFactory.Parse(template, defaults, parameterPolicies: null),
+                RoutePatternFactory.Parse(template, defaults, parameterPolicies: null, requiredValues),
                 order,
-                metadataCollection,
+                new EndpointMetadataCollection(metadata),
                 null);
         }
 

src/Mvc/test/Microsoft.AspNetCore.Mvc.Core.Test/Routing/PageLinkGeneratorExtensionsTest.cs

@@ -25,11 +25,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "About/{id}",
                 defaults: new { page = "/About", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/About", })) });
+                requiredValues:new { page = "/About", });
             var endpoint2 = CreateEndpoint(
                 "Admin/ManageUsers/{handler?}",
                 defaults: new { page = "/Admin/ManageUsers", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/Admin/ManageUsers", })) });
+                requiredValues:new { page = "/Admin/ManageUsers", });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -54,11 +54,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "About/{id}",
                 defaults: new { page = "/About", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/About", })) });
+                requiredValues:new { page = "/About", });
             var endpoint2 = CreateEndpoint(
                 "Admin/ManageUsers/{handler?}",
                 defaults: new { page = "/Admin/ManageUsers", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/Admin/ManageUsers", })) });
+                requiredValues:new { page = "/Admin/ManageUsers", });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -82,11 +82,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "About/{id}",
                 defaults: new { page = "/About", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/About", })) });
+                requiredValues:new { page = "/About", });
             var endpoint2 = CreateEndpoint(
                 "Admin/ManageUsers",
                 defaults: new { page = "/Admin/ManageUsers", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/Admin/ManageUsers", })) });
+                requiredValues:new { page = "/Admin/ManageUsers", });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -112,11 +112,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "About/{id}",
                 defaults: new { page = "/About", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/About", })) });
+                requiredValues:new { page = "/About", });
             var endpoint2 = CreateEndpoint(
                 "Admin/ManageUsers",
                 defaults: new { page = "/Admin/ManageUsers", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/Admin/ManageUsers", })) });
+                requiredValues:new { page = "/Admin/ManageUsers", });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -142,11 +142,11 @@ namespace Microsoft.AspNetCore.Routing
             var endpoint1 = CreateEndpoint(
                 "About/{id}",
                 defaults: new { page = "/About", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/About", })) });
+                requiredValues:new { page = "/About", });
             var endpoint2 = CreateEndpoint(
                 "Admin/ManageUsers",
                 defaults: new { page = "/Admin/ManageUsers", },
-                metadata: new[] { new RouteValuesAddressMetadata(routeName: null, new RouteValueDictionary(new { page = "/Admin/ManageUsers", })) });
+                requiredValues:new { page = "/Admin/ManageUsers", });
 
             var linkGenerator = CreateLinkGenerator(endpoint1, endpoint2);
 
@@ -175,7 +175,7 @@ namespace Microsoft.AspNetCore.Routing
         {
             return new RouteEndpoint(
                 (httpContext) => Task.CompletedTask,
-                RoutePatternFactory.Parse(template, defaults, parameterPolicies: null),
+                RoutePatternFactory.Parse(template, defaults, parameterPolicies: null, requiredValues),
                 order,
                 new EndpointMetadataCollection(metadata ?? Array.Empty<object>()),
                 null);

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

@@ -323,7 +323,7 @@ Hello from page";
             var expected =
 @"<a href=""/Accounts/Manage/RenderPartials"">Link inside area</a>
 <a href=""/Products/List/old/20"">Link to external area</a>
-<a href=""/Accounts"">Link to area action</a>
+<a href="""">Link to area action</a>
 <a href=""/Admin"">Link to non-area page</a>";
 
             // Act

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

@@ -1294,8 +1294,6 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             Assert.Equal("/", result.Link);
         }
 
-
-
         [Fact]
         public virtual async Task AttributeRoutedAction_InArea_LinkToConventionalRoutedActionInArea()
         {

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/compiler/resources/TagHelpersWebSite.Home.About.html

@@ -1,4 +1,4 @@
-
+
 
 <!DOCTYPE html>
 <html>
@@ -12,8 +12,8 @@
 <body>
     <h1 style="font-family: cursive;">ASP.NET vNext - About</h1>
     <p>| <a href="/" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Home</a>
-       | <a href="/Home/About" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My About</a> 
+       | <a href="/home/about" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My About</a> 
-       | <a href="/Home/Help" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Help</a> |</p>
+       | <a href="/home/help" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Help</a> |</p>
     <div>
         
 

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/compiler/resources/TagHelpersWebSite.Home.Help.html

@@ -1,4 +1,4 @@
-
+
 
 <!DOCTYPE html>
 <html>
@@ -12,8 +12,8 @@
 <body>
     <h1 style="font-family: cursive;">ASP.NET vNext - Help</h1>
     <p>| <a href="/" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Home</a>
-       | <a href="/Home/About" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My About</a> 
+       | <a href="/home/about" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My About</a> 
-       | <a href="/Home/Help" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Help</a> |</p>
+       | <a href="/home/help" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Help</a> |</p>
     <div>
         
 

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/compiler/resources/TagHelpersWebSite.Home.Index.html

@@ -1,4 +1,4 @@
-
+
 
 <!DOCTYPE html>
 <html>
@@ -19,8 +19,8 @@
 <body>
     <h1 style="font-family: cursive;">ASP.NET vNext - Home Page</h1>
     <p>| <a href="/" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Home</a>
-       | <a href="/Home/About" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My About</a> 
+       | <a href="/home/about" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My About</a> 
-       | <a href="/Home/Help" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Help</a> |</p>
+       | <a href="/home/help" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Help</a> |</p>
     <div>
         
 

src/Mvc/test/Microsoft.AspNetCore.Mvc.FunctionalTests/compiler/resources/TagHelpersWebSite.Home.ViewComponentTagHelpers.html

@@ -1,4 +1,4 @@
-
+
 
 <!DOCTYPE html>
 <html>
@@ -12,8 +12,8 @@
 <body>
     <h1 style="font-family: cursive;">ASP.NET vNext - </h1>
     <p>| <a href="/" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Home</a>
-       | <a href="/Home/About" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My About</a> 
+       | <a href="/home/about" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My About</a> 
-       | <a href="/Home/Help" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Help</a> |</p>
+       | <a href="/home/help" style="background-color: gray;color: white;border-radius: 3px;border: 1px solid black;padding: 3px;font-family: cursive;">My Help</a> |</p>
     <div>
         
 <div>Items: </div>

src/Mvc/test/WebSites/RoutingWebSite/Controllers/DebugController.cs

@@ -0,0 +1,31 @@
+// 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.IO;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Routing;
+using Microsoft.AspNetCore.Routing.Internal;
+
+namespace RoutingWebSite
+{
+    // This controller is reachable via traditional routing.
+    public class DebugController : Controller
+    {
+        private readonly DfaGraphWriter _graphWriter;
+        private readonly EndpointDataSource _endpointDataSource;
+
+        public DebugController(DfaGraphWriter graphWriter, EndpointDataSource endpointDataSource)
+        {
+            _graphWriter = graphWriter;
+            _endpointDataSource = endpointDataSource;
+        }
+
+        public IActionResult Graph()
+        {
+            var sw = new StringWriter();
+            _graphWriter.Write(_endpointDataSource, sw);
+
+            return Content(sw.ToString());
+        }
+    }
+}

src/Mvc/test/WebSites/RoutingWebSite/Startup.cs

@@ -1,12 +1,14 @@
 // 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.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.ApplicationModels;
 using Microsoft.AspNetCore.Mvc.Infrastructure;
 using Microsoft.AspNetCore.Routing;
+using Microsoft.AspNetCore.Routing.Matching;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace RoutingWebSite