Fix TreeMatcher's use of EndpointSelector (#551)

src/Microsoft.AspNetCore.Routing/Matchers/TreeMatcher.cs

@@ -141,37 +141,31 @@ namespace Microsoft.AspNetCore.Routing.Matchers
 
         private Task SelectEndpointAsync(HttpContext httpContext, IEndpointFeature feature, IReadOnlyList<MatcherEndpoint> endpoints)
         {
-            var bestEndpoint = _endpointSelector.SelectBestCandidate(httpContext, endpoints);
+            MatcherEndpoint endpoint;
 
-            // REVIEW: Note that this code doesn't do anything significant now. This will eventually incorporate something like IActionConstraint
-            switch (endpoints.Count)
+            try
             {
-                case 0:
-                    {
-                        Log.MatchFailed(_logger, httpContext);
-                        return Task.CompletedTask;
-                    }
-
-                case 1:
-                    {
-                        var endpoint = endpoints[0];
-                        Log.MatchSuccess(_logger, httpContext, endpoint);
-
-                        feature.Endpoint = endpoint;
-                        feature.Invoker = endpoint.Invoker;
-
-                        return Task.CompletedTask;
-                    }
-
-                default:
-                    {
-                        Log.MatchAmbiguous(_logger, httpContext, endpoints);
-                        var message = Resources.FormatAmbiguousEndpoints(
-                            Environment.NewLine,
-                            string.Join(Environment.NewLine, endpoints.Select(a => a.DisplayName)));
-                        throw new AmbiguousMatchException(message);
-                    }
+                endpoint = (MatcherEndpoint)_endpointSelector.SelectBestCandidate(httpContext, endpoints);
             }
+            catch (Exception ex)
+            {
+                // Handle AmbiguousMatchException from EndpointSelector
+                return Task.FromException(ex);
+            }
+
+            if (endpoint == null)
+            {
+                Log.MatchFailed(_logger, httpContext);
+            }
+            else
+            {
+                Log.MatchSuccess(_logger, httpContext, endpoint);
+
+                feature.Endpoint = endpoint;
+                feature.Invoker = endpoint.Invoker;
+            }
+
+            return Task.CompletedTask;
         }
 
         private UrlMatchingTree[] CreateTrees(IReadOnlyList<Endpoint> endpoints)

test/Microsoft.AspNetCore.Routing.Tests/Matchers/TreeMatcherTests.cs

@@ -15,9 +15,9 @@ namespace Microsoft.AspNetCore.Routing.Matchers
 {
     public class TreeMatcherTests
     {
-        private MatcherEndpoint CreateEndpoint(string template, int order, object values = null)
+        private MatcherEndpoint CreateEndpoint(string template, int order, object values = null, EndpointMetadataCollection metadata = null)
         {
-            return new MatcherEndpoint((next) => null, template, values, order, EndpointMetadataCollection.Empty, template);
+            return new MatcherEndpoint((next) => null, template, values, order, metadata ?? EndpointMetadataCollection.Empty, template);
         }
 
         private TreeMatcher CreateTreeMatcher(EndpointDataSource endpointDataSource)
@@ -58,5 +58,36 @@ namespace Microsoft.AspNetCore.Routing.Matchers
             // Assert
             Assert.Equal(lowerOrderEndpoint, endpointFeature.Endpoint);
         }
+
+        [Fact]
+        public async Task MatchAsync_MultipleMatches_EndpointSelectorCalled()
+        {
+            // Arrange
+            var endpointWithoutConstraint = CreateEndpoint("/Teams", 0);
+            var endpointWithConstraint = CreateEndpoint(
+                "/Teams",
+                0,
+                metadata: new EndpointMetadataCollection(new object[] { new HttpMethodEndpointConstraint(new[] { "POST" }) }));
+
+            var endpointDataSource = new DefaultEndpointDataSource(new List<Endpoint>
+            {
+                endpointWithoutConstraint,
+                endpointWithConstraint
+            });
+
+            var treeMatcher = CreateTreeMatcher(endpointDataSource);
+
+            var httpContext = new DefaultHttpContext();
+            httpContext.Request.Method = "POST";
+            httpContext.Request.Path = "/Teams";
+
+            var endpointFeature = new EndpointFeature();
+
+            // Act
+            await treeMatcher.MatchAsync(httpContext, endpointFeature);
+
+            // Assert
+            Assert.Equal(endpointWithConstraint, endpointFeature.Endpoint);
+        }
     }
 }