Updated the AddPolicyRegistry extension methods to use TryAdd and TryAddEnumerable internally (#47821)

* Added TryAddPolicyRegistry extension methods for IPolicyRegistry

* Added missing using statement

* Undone changes on PublicAPI.Shipped.txt

* Added the TryAddPolicyRegistry extension methods to the PublicAPI.Unshipped.txt

* Updated the AddPolicyRegistry extension methods to use TryAdd and TryAddEnumerable internally

* Trigger again build pipeline

* Updated the AddPolicyRegistry extension methods to fix failing unit tests

* Updated the AddPolicyRegistry extension methods and added unit tests

* Revert global.json changes

* Revert global.json changes to latest version

* Revert global.json changes to latest version

* Fixed unit tests

* Added missing using statement in unit tests

* Updated only the parameterless AddPolicyRegistry overload to an add-if-missing operation

* Cleanup. Added missing space

---------

Co-authored-by: Iustin Micu <[email protected]>

Author: Arclight3

src/HttpClientFactory/Polly/src/DependencyInjection/PollyServiceCollectionExtensions.cs

@@ -3,6 +3,7 @@
 
 using System;
 using Polly.Registry;
+using Microsoft.Extensions.DependencyInjection.Extensions;
 
 namespace Microsoft.Extensions.DependencyInjection;
 
@@ -15,24 +16,33 @@ public static class PollyServiceCollectionExtensions
     /// <summary>
     /// Registers an empty <see cref="PolicyRegistry"/> in the service collection with service types
     /// <see cref="IPolicyRegistry{String}"/>, <see cref="IReadOnlyPolicyRegistry{String}"/>, and
-    /// <see cref="IConcurrentPolicyRegistry{String}"/> and returns the newly created registry.
+     /// <see cref="IConcurrentPolicyRegistry{String}"/> if the service types haven't already been registered
+    /// and returns the existing or newly created registry.
     /// </summary>
     /// <param name="services">The <see cref="IServiceCollection"/>.</param>
-    /// <returns>The newly created <see cref="IPolicyRegistry{String}"/>.</returns>
+    /// <returns>The existing or newly created <see cref="IPolicyRegistry{String}"/>.</returns>
     public static IPolicyRegistry<string> AddPolicyRegistry(this IServiceCollection services)
     {
         if (services == null)
         {
             throw new ArgumentNullException(nameof(services));
         }
 
-        // Create an empty registry, register and return it as an instance. This is the best way to get a
-        // single instance registered using all the interfaces.
-        var registry = new PolicyRegistry();
+        // Get existing registry or an empty instance
+        var registry = services.BuildServiceProvider().GetService<IPolicyRegistry<string>>();
+        if (registry == null)
+        {
+            registry = new PolicyRegistry();
+        }
 
-        services.AddSingleton<IConcurrentPolicyRegistry<string>>(registry);
-        services.AddSingleton<IPolicyRegistry<string>>(registry);
-        services.AddSingleton<IReadOnlyPolicyRegistry<string>>(registry);
+        // Try to register for the missing interfaces
+        services.TryAddEnumerable(ServiceDescriptor.Singleton<IPolicyRegistry<string>>(registry));
+        services.TryAddEnumerable(ServiceDescriptor.Singleton<IReadOnlyPolicyRegistry<string>>(registry));
+
+        if (registry is IConcurrentPolicyRegistry<string> concurrentRegistry)
+        {
+            services.TryAddEnumerable(ServiceDescriptor.Singleton<IConcurrentPolicyRegistry<string>>(concurrentRegistry));
+        }
 
         return registry;
     }

src/HttpClientFactory/Polly/test/DependencyInjection/PollyHttpClientBuilderExtensionsTest.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Net;
 using System.Net.Http;
 using System.Threading;
@@ -522,6 +523,63 @@ public void AddPolicyHandlerFromRegistry_WithConfigureDelegate_AddsPolicyRegistr
         Assert.Same(registry, services.GetService<IReadOnlyPolicyRegistry<string>>());
     }
 
+    [Fact]
+    public void AddPolicyRegistry_DoesNotOverrideOrAddExtraRegistrations()
+    {
+        // Arrange
+        var serviceCollection = new ServiceCollection();
+
+        // Act 1
+        var existingRegistry = serviceCollection.AddPolicyRegistry();
+
+        // Act 2
+        var registry = serviceCollection.AddPolicyRegistry();
+        var services = serviceCollection.BuildServiceProvider();
+
+        // Assert
+        Assert.NotNull(existingRegistry);
+        Assert.Same(existingRegistry, registry);
+
+        Assert.Same(existingRegistry, services.GetService<IPolicyRegistry<string>>());
+        Assert.Same(existingRegistry, services.GetService<IConcurrentPolicyRegistry<string>>());
+        Assert.Same(existingRegistry, services.GetService<IReadOnlyPolicyRegistry<string>>());
+
+        Assert.Single(serviceCollection, sd => sd.ServiceType == typeof(IPolicyRegistry<string>));
+        Assert.Single(serviceCollection, sd => sd.ServiceType == typeof(IReadOnlyPolicyRegistry<string>));
+        Assert.Single(serviceCollection, sd => sd.ServiceType == typeof(IConcurrentPolicyRegistry<string>));
+    }
+
+    [Theory]
+    [InlineData(typeof(IPolicyRegistry<string>))]
+    [InlineData(typeof(IReadOnlyPolicyRegistry<string>))]
+    [InlineData(typeof(IConcurrentPolicyRegistry<string>))]
+    public void AddPolicyRegistry_AddsOnlyMissingRegistrations(Type missingType)
+    {
+        // Arrange
+        var serviceCollection = new ServiceCollection();
+        var registry = new PolicyRegistry();
+        var policyTypes = new List<Type>
+        {
+            typeof(IPolicyRegistry<string>),
+            typeof(IReadOnlyPolicyRegistry<string>),
+            typeof(IConcurrentPolicyRegistry<string>)
+        };
+
+        // Act 1
+        foreach (var policyType in policyTypes.Where(x => x != missingType))
+        {
+            serviceCollection.AddSingleton(policyType, registry);
+        }
+
+        // Act 2
+        serviceCollection.AddPolicyRegistry();
+
+        // Assert
+        Assert.Single(serviceCollection, sd => sd.ServiceType == typeof(IPolicyRegistry<string>));
+        Assert.Single(serviceCollection, sd => sd.ServiceType == typeof(IReadOnlyPolicyRegistry<string>));
+        Assert.Single(serviceCollection, sd => sd.ServiceType == typeof(IConcurrentPolicyRegistry<string>));
+    }
+
     // Throws an exception or fails on even numbered requests, otherwise succeeds.
     private class FaultyMessageHandler : DelegatingHandler
     {