Fix HttpContext not being passed to constraints in link generation (#6644)

Author: JamesNK

src/Http/Routing/src/DefaultLinkGenerator.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// 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;
@@ -90,6 +90,7 @@ public override string GetPathByAddress<TAddress>(
             }
 
             return GetPathByEndpoints(
+                httpContext,
                 endpoints,
                 values,
                 ambientValues,
@@ -112,6 +113,7 @@ public override string GetPathByAddress<TAddress>(
             }
 
             return GetPathByEndpoints(
+                httpContext: null,
                 endpoints,
                 values,
                 ambientValues: null,
@@ -206,7 +208,8 @@ private List<RouteEndpoint> GetEndpoints<TAddress>(TAddress address)
             return endpoints;
         }
 
-        public string GetPathByEndpoints(
+        private string GetPathByEndpoints(
+            HttpContext httpContext,
             List<RouteEndpoint> endpoints,
             RouteValueDictionary values,
             RouteValueDictionary ambientValues,
@@ -218,7 +221,7 @@ public string GetPathByEndpoints(
             {
                 var endpoint = endpoints[i];
                 if (TryProcessTemplate(
-                    httpContext: null,
+                    httpContext: httpContext,
                     endpoint: endpoint,
                     values: values,
                     ambientValues: ambientValues,

src/Http/Routing/test/UnitTests/DefaultLinkGeneratorTest.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// 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;
@@ -524,6 +524,42 @@ public void GetUriByAddress_WithHttpContext_CanOverrideUriParts()
             Assert.Equal("ftp://example.com:5000/Home/Index", uri);
         }
 
+        [Fact]
+        public void GetPathByAddress_WithHttpContext_ContextPassedToConstraint()
+        {
+            // Arrange
+            var constraint = new TestRouteConstraint();
+
+            var endpoint1 = EndpointFactory.CreateRouteEndpoint("{controller}/{action}/{id?}", policies: new { controller = constraint }, metadata: new object[] { new IntMetadata(1), });
+
+            var linkGenerator = CreateLinkGenerator(endpoint1);
+
+            var httpContext = CreateHttpContext();
+            httpContext.Request.PathBase = "/Foo";
+
+            // Act
+            var uri = linkGenerator.GetPathByAddress(
+                httpContext,
+                1,
+                values: new RouteValueDictionary(new { action = "Index", controller = "Home", }),
+                pathBase: "/");
+
+            // Assert
+            Assert.Equal("/Home/Index", uri);
+            Assert.True(constraint.HasHttpContext);
+        }
+
+        private class TestRouteConstraint : IRouteConstraint
+        {
+            public bool HasHttpContext { get; set; }
+
+            public bool Match(HttpContext httpContext, IRouter route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
+            {
+                HasHttpContext = (httpContext != null);
+                return true;
+            }
+        }
+
         [Fact]
         public void GetTemplateBinder_CanCache()
         {