Fix DfaGraphWriter ISuppressMatchingMetadata check (#850)

Author: JamesNK

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

@@ -38,7 +38,7 @@ public void Write(EndpointDataSource dataSource, TextWriter writer)
             var endpoints = dataSource.Endpoints;
             for (var i = 0; i < endpoints.Count; i++)
             {
-                if (endpoints[i] is RouteEndpoint endpoint && endpoint.Metadata.GetMetadata<ISuppressMatchingMetadata>()?.SuppressMatching == true)
+                if (endpoints[i] is RouteEndpoint endpoint && (endpoint.Metadata.GetMetadata<ISuppressMatchingMetadata>()?.SuppressMatching ?? false) == false)
                 {
                     builder.AddEndpoint(endpoint);
                 }

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

@@ -0,0 +1,95 @@
+// 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.Http;
+using Microsoft.AspNetCore.Routing.Patterns;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Primitives;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Routing.Internal
+{
+    public class DfaGraphWriterTest
+    {
+        private DfaGraphWriter CreateGraphWriter()
+        {
+            ServiceCollection services = new ServiceCollection();
+            services.AddLogging();
+            services.AddRouting();
+
+            return new DfaGraphWriter(services.BuildServiceProvider());
+        }
+
+        [Fact]
+        public void Write_ExcludeNonRouteEndpoint()
+        {
+            // Arrange
+            var graphWriter = CreateGraphWriter();
+            var writer = new StringWriter();
+            var endpointsDataSource = new DefaultEndpointDataSource(new Endpoint((context) => null, EndpointMetadataCollection.Empty, string.Empty));
+
+            // Act
+            graphWriter.Write(endpointsDataSource, writer);
+
+            // Assert
+            Assert.Equal(@"digraph DFA {
+0 [label=""/""]
+}
+", writer.ToString());
+        }
+
+        [Fact]
+        public void Write_ExcludeRouteEndpointWithSuppressMatchingMetadata()
+        {
+            // Arrange
+            var graphWriter = CreateGraphWriter();
+            var writer = new StringWriter();
+            var endpointsDataSource = new DefaultEndpointDataSource(
+                new RouteEndpoint(
+                    (context) => null,
+                    RoutePatternFactory.Parse("/"),
+                    0,
+                    new EndpointMetadataCollection(new SuppressMatchingMetadata()),
+                    string.Empty));
+
+            // Act
+            graphWriter.Write(endpointsDataSource, writer);
+
+            // Assert
+            Assert.Equal(@"digraph DFA {
+0 [label=""/""]
+}
+", writer.ToString());
+        }
+
+        [Fact]
+        public void Write_IncludeRouteEndpointWithPolicy()
+        {
+            // Arrange
+            var graphWriter = CreateGraphWriter();
+            var writer = new StringWriter();
+            var endpointsDataSource = new DefaultEndpointDataSource(
+                new RouteEndpoint(
+                    (context) => null,
+                    RoutePatternFactory.Parse("/"),
+                    0,
+                    new EndpointMetadataCollection(new HttpMethodMetadata(new[] { "GET" })),
+                    string.Empty));
+
+            // Act
+            graphWriter.Write(endpointsDataSource, writer);
+
+            // Assert
+            var sdf = writer.ToString();
+            Assert.Equal(@"digraph DFA {
+0 [label=""/ HTTP: GET""]
+1 [label=""/ HTTP: *""]
+2 -> 0 [label=""HTTP: GET""]
+2 -> 1 [label=""HTTP: *""]
+2 [label=""/""]
+}
+", sdf);
+        }
+    }
+}