Support supression of matching for endpoints

src/Microsoft.AspNetCore.Routing/ISuppressMatchingMetadata.cs

@@ -0,0 +1,13 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Routing
+{
+    /// <summary>
+    /// Metadata used to prevent URL matching. The associated endpoint will not be
+    /// considered URL matching for incoming requests.
+    /// </summary>
+    public interface ISuppressMatchingMetadata
+    {
+    }
+}

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

@@ -39,7 +39,7 @@ namespace Microsoft.AspNetCore.Routing.Internal
             for (var i = 0; i < endpoints.Count; i++)
             {
                 var endpoint = endpoints[i] as MatcherEndpoint;
-                if (endpoint != null)
+                if (endpoint != null && endpoint.Metadata.GetMetadata<ISuppressMatchingMetadata>() == null)
                 {
                     builder.AddEndpoint(endpoint);
                 }

src/Microsoft.AspNetCore.Routing/Matching/DataSourceDependentMatcher.cs

@@ -40,7 +40,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
                 // register other endpoint types, which are non-routable, and it's
                 // ok that we won't route to them.
                 var endpoint = endpoints[i] as MatcherEndpoint;
-                if (endpoint != null)
+                if (endpoint != null && endpoint.Metadata.GetMetadata<ISuppressMatchingMetadata>() == null)
                 {
                     builder.AddEndpoint(endpoint);
                 }

src/Microsoft.AspNetCore.Routing/SuppressMatchingMetadata.cs

@@ -0,0 +1,13 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Routing
+{
+    /// <summary>
+    /// Metadata used to prevent URL matching. The associated endpoint will not be
+    /// considered URL matching for incoming requests.
+    /// </summary>
+    public sealed class SuppressMatchingMetadata : ISuppressMatchingMetadata
+    {
+    }
+}

test/Microsoft.AspNetCore.Routing.Tests/Matching/DataSourceDependentMatcherTest.cs

@@ -67,6 +67,27 @@ namespace Microsoft.AspNetCore.Routing.Matching
             Assert.Empty(inner.Endpoints);
         }
 
+        [Fact]
+        public void Matcher_Ignores_SuppressedEndpoint()
+        {
+            // Arrange
+            var dataSource = new DynamicEndpointDataSource();
+            var endpoint = new MatcherEndpoint(
+                MatcherEndpoint.EmptyInvoker,
+                RoutePatternFactory.Parse("/"),
+                0,
+                new EndpointMetadataCollection(new SuppressMatchingMetadata()),
+                "test");
+            dataSource.AddEndpoint(endpoint);
+
+            // Act
+            var matcher = new DataSourceDependentMatcher(dataSource, TestMatcherBuilder.Create);
+
+            // Assert
+            var inner = Assert.IsType<TestMatcher>(matcher.CurrentMatcher);
+            Assert.Empty(inner.Endpoints);
+        }
+
         [Fact]
         public void Cache_Reinitializes_WhenDataSourceChanges()
         {