Addressed code review comments.

Author: N. Taylor Mullen

src/Http/Routing/src/EndpointRoutingMiddleware.cs

@@ -52,7 +52,7 @@ public Task Invoke(HttpContext httpContext)
             {
                 Log.MatchSkipped(_logger, endpoint);
 
-                // Someone else set the endpoint, we'll let them handle the unsetting.
+                // Someone else set the endpoint, we'll let them handle the clearing of the endpoint.
                 return _next(httpContext);
             }
 
@@ -88,7 +88,6 @@ static async Task AwaitMatch(EndpointRoutingMiddleware middleware, HttpContext h
 
         }
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private async Task SetRoutingAndContinue(HttpContext httpContext)
         {
             // If there was no mutation of the endpoint then log failure
@@ -115,8 +114,7 @@ private async Task SetRoutingAndContinue(HttpContext httpContext)
             }
             finally
             {
-                // We unset the endpoint after calling through to the next middleware. This enables any future calls into
-                // endpoint routing don't no-op from there already being an endpoint set.
+                // This allows a second call in a single request (such as from the ErrorHandlerMiddleware) to perform routing again.
                 httpContext.SetEndpoint(endpoint: null);
             }
         }

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

@@ -20,6 +20,48 @@ namespace Microsoft.AspNetCore.Routing
 {
     public class EndpointRoutingMiddlewareTest
     {
+        [Fact]
+        public async Task Invoke_ChangedPath_ResultsInDifferentResult()
+        {
+            // Arrange
+            var httpContext = CreateHttpContext();
+            var matcher = new Mock<Matcher>();
+            var pathToEndpoints = new Dictionary<string, Endpoint>()
+            {
+                ["/initial"] = new Endpoint(c => Task.CompletedTask, new EndpointMetadataCollection(), "initialEndpoint"),
+                ["/changed"] = new Endpoint(c => Task.CompletedTask, new EndpointMetadataCollection(), "changedEndpoint")
+            };
+            matcher.Setup(m => m.MatchAsync(httpContext))
+                .Callback<HttpContext>(context =>
+                {
+                    var endpointToSet = pathToEndpoints[context.Request.Path];
+                    context.SetEndpoint(endpointToSet);
+                })
+                .Returns(Task.CompletedTask)
+                .Verifiable();
+            var matcherFactory = Mock.Of<MatcherFactory>(factory => factory.CreateMatcher(It.IsAny<EndpointDataSource>()) == matcher.Object);
+            var middleware = CreateMiddleware(
+                matcherFactory: matcherFactory,
+                next: context =>
+                {
+                    Assert.True(pathToEndpoints.TryGetValue(context.Request.Path, out var expectedEndpoint));
+
+                    var currentEndpoint = context.GetEndpoint();
+                    Assert.Equal(expectedEndpoint, currentEndpoint);
+
+                    return Task.CompletedTask;
+                });
+
+            // Act
+            httpContext.Request.Path = "/initial";
+            await middleware.Invoke(httpContext);
+            httpContext.Request.Path = "/changed";
+            await middleware.Invoke(httpContext);
+
+            // Assert
+            matcher.Verify();
+        }
+
         [Fact]
         public async Task Invoke_OnException_ResetsEndpoint()
         {