From 7bb56a8dba0716a528136fa69853615eb5f46793 Mon Sep 17 00:00:00 2001
From: Pranav K <prkrishn@hotmail.com>
Date: Wed, 21 Aug 2019 13:18:41 -0700
Subject: [PATCH] Do not throw if RouteComparison compares two identical
 references

Fixes https://github.com/aspnet/AspNetCore/issues/13313
---
 .../Components/src/Routing/RouteEntry.cs      |  2 ++
 .../src/Routing/RouteTableFactory.cs          |  5 +++
 .../Components/src/Routing/RouteTemplate.cs   |  3 ++
 .../test/Routing/RouteTableFactoryTests.cs    | 35 +++++++++++++++++++
 4 files changed, 45 insertions(+)

diff --git a/src/Components/Components/src/Routing/RouteEntry.cs b/src/Components/Components/src/Routing/RouteEntry.cs
index 3870ef2245..d2bca6d2a7 100644
--- a/src/Components/Components/src/Routing/RouteEntry.cs
+++ b/src/Components/Components/src/Routing/RouteEntry.cs
@@ -3,9 +3,11 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 
 namespace Microsoft.AspNetCore.Components.Routing
 {
+    [DebuggerDisplay("Handler = {Handler}, Template = {Template}")]
     internal class RouteEntry
     {
         public RouteEntry(RouteTemplate template, Type handler, string[] unusedRouteParameterNames)
diff --git a/src/Components/Components/src/Routing/RouteTableFactory.cs b/src/Components/Components/src/Routing/RouteTableFactory.cs
index fc148b708a..de6fe31c1d 100644
--- a/src/Components/Components/src/Routing/RouteTableFactory.cs
+++ b/src/Components/Components/src/Routing/RouteTableFactory.cs
@@ -114,6 +114,11 @@ namespace Microsoft.AspNetCore.Components
         /// </summary>
         internal static int RouteComparison(RouteEntry x, RouteEntry y)
         {
+            if (ReferenceEquals(x, y))
+            {
+                return 0;
+            }
+
             var xTemplate = x.Template;
             var yTemplate = y.Template;
             if (xTemplate.Segments.Length != y.Template.Segments.Length)
diff --git a/src/Components/Components/src/Routing/RouteTemplate.cs b/src/Components/Components/src/Routing/RouteTemplate.cs
index bb59be07ee..a79f0f911a 100644
--- a/src/Components/Components/src/Routing/RouteTemplate.cs
+++ b/src/Components/Components/src/Routing/RouteTemplate.cs
@@ -2,8 +2,11 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 
+using System.Diagnostics;
+
 namespace Microsoft.AspNetCore.Components.Routing
 {
+    [DebuggerDisplay("{TemplateText}")]
     internal class RouteTemplate
     {
         public RouteTemplate(string templateText, TemplateSegment[] segments)
diff --git a/src/Components/Components/test/Routing/RouteTableFactoryTests.cs b/src/Components/Components/test/Routing/RouteTableFactoryTests.cs
index 89bf2db1cc..92bea90d79 100644
--- a/src/Components/Components/test/Routing/RouteTableFactoryTests.cs
+++ b/src/Components/Components/test/Routing/RouteTableFactoryTests.cs
@@ -366,6 +366,41 @@ namespace Microsoft.AspNetCore.Components.Test.Routing
             Assert.Equal("a/brilliant", routeTable.Routes[0].Template.TemplateText);
         }
 
+        [Fact]
+        public void DoesNotThrowIfStableSortComparesRouteWithItself()
+        {
+            // Test for https://github.com/aspnet/AspNetCore/issues/13313
+            // Arrange & Act
+            var builder = new TestRouteTableBuilder();
+            builder.AddRoute("r16");
+            builder.AddRoute("r05");
+            builder.AddRoute("r09");
+            builder.AddRoute("r00");
+            builder.AddRoute("r13");
+            builder.AddRoute("r02");
+            builder.AddRoute("r03");
+            builder.AddRoute("r10");
+            builder.AddRoute("r15");
+            builder.AddRoute("r14");
+            builder.AddRoute("r12");
+            builder.AddRoute("r07");
+            builder.AddRoute("r11");
+            builder.AddRoute("r08");
+            builder.AddRoute("r06");
+            builder.AddRoute("r04");
+            builder.AddRoute("r01");
+
+            var routeTable = builder.Build();
+
+            // Act
+            Assert.Equal(17, routeTable.Routes.Length);
+            for (var i = 0; i < 17; i++)
+            {
+                var templateText = "r" + i.ToString().PadLeft(2, '0');
+                Assert.Equal(templateText, routeTable.Routes[i].Template.TemplateText);
+            }
+        }
+
         [Theory]
         [InlineData("/literal", "/Literal/")]
         [InlineData("/{parameter}", "/{parameter}/")]