Merge branch 'release/3.1' => 'blazor-wasm' (#17120)

NuGet.config

@@ -2,9 +2,6 @@
 <configuration>
   <packageSources>
     <clear />
-    <!--Begin: Package sources managed by Dependency Flow automation. Do not edit the sources below.-->
-    <add key="darc-pub-dotnet-core-setup-7d57652" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/darc-pub-dotnet-core-setup-7d57652f/nuget/v3/index.json" />
-    <!--End: Package sources managed by Dependency Flow automation. Do not edit the sources above.-->
     <add key="dotnet-core" value="https://dotnetfeed.blob.core.windows.net/dotnet-core/index.json" />
     <add key="dotnet-tools" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-tools/nuget/v3/index.json" />
     <add key="aspnet-blazor" value="https://dotnetfeed.blob.core.windows.net/aspnet-blazor/index.json" />

src/Components/Components/src/Routing/RouteConstraint.cs

@@ -2,15 +2,20 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.Globalization;
 
 namespace Microsoft.AspNetCore.Components.Routing
 {
     internal abstract class RouteConstraint
     {
-        private static readonly IDictionary<string, RouteConstraint> _cachedConstraints
-            = new Dictionary<string, RouteConstraint>();
+        // note: the things that prevent this cache from growing unbounded is that
+        // we're the only caller to this code path, and the fact that there are only
+        // 8 possible instances that we create.
+        //
+        // The values passed in here for parsing are always static text defined in route attributes.
+        private static readonly ConcurrentDictionary<string, RouteConstraint> _cachedConstraints
+            = new ConcurrentDictionary<string, RouteConstraint>();
 
         public abstract bool Match(string pathSegment, out object convertedValue);
 
@@ -30,8 +35,10 @@ namespace Microsoft.AspNetCore.Components.Routing
                 var newInstance = CreateRouteConstraint(constraint);
                 if (newInstance != null)
                 {
-                    _cachedConstraints[constraint] = newInstance;
-                    return newInstance;
+                    // We've done to the work to create the constraint now, but it's possible
+                    // we're competing with another thread. GetOrAdd can ensure only a single
+                    // instance is returned so that any extra ones can be GC'ed.
+                    return _cachedConstraints.GetOrAdd(constraint, newInstance);
                 }
                 else
                 {

src/Components/Components/test/Routing/RouteConstraintTest.cs

@@ -0,0 +1,36 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Components.Routing
+{
+    public class RouteConstraintTest
+    {
+        [Fact]
+        public void Parse_CreatesDifferentConstraints_ForDifferentKinds()
+        {
+            // Arrange
+            var original = RouteConstraint.Parse("ignore", "ignore", "int");
+
+            // Act
+            var another = RouteConstraint.Parse("ignore", "ignore", "guid");
+
+            // Assert
+            Assert.NotSame(original, another);
+        }
+
+        [Fact]
+        public void Parse_CachesCreatedConstraint_ForSameKind()
+        {
+            // Arrange
+            var original = RouteConstraint.Parse("ignore", "ignore", "int");
+
+            // Act
+            var another = RouteConstraint.Parse("ignore", "ignore", "int");
+
+            // Assert
+            Assert.Same(original, another);
+        }
+    }
+}