Expose the ResilienceHandler type.

Fixes #4759

src/Libraries/Microsoft.Extensions.Http.Resilience/Microsoft.Extensions.Http.Resilience.csproj

@@ -15,6 +15,7 @@
  <InjectSharedDataValidation>true</InjectSharedDataValidation>
  <InjectSharedPools>true</InjectSharedPools>
  <InjectSharedDiagnosticIds>true</InjectSharedDiagnosticIds>
+ <InjectExperimentalAttributeOnLegacy>true</InjectExperimentalAttributeOnLegacy>
  </PropertyGroup>
 
  <PropertyGroup>

src/Libraries/Microsoft.Extensions.Http.Resilience/Resilience/Internal/ResilienceHandler.cs → src/Libraries/Microsoft.Extensions.Http.Resilience/Resilience/ResilienceHandler.cs

@@ -2,29 +2,58 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Http.Diagnostics;
+using Microsoft.Extensions.Http.Resilience.Internal;
+using Microsoft.Shared.DiagnosticIds;
+using Microsoft.Shared.Diagnostics;
 using Polly;
 
-namespace Microsoft.Extensions.Http.Resilience.Internal;
+namespace Microsoft.Extensions.Http.Resilience;
 
 /// <summary>
-/// Base class for resilience handler, i.e. handlers that use resilience strategies  to send the requests.
+/// Base class for resilience handler, i.e. handlers that use resilience strategies to send the requests.
 /// </summary>
-internal sealed class ResilienceHandler : DelegatingHandler
+[Experimental(diagnosticId: DiagnosticIds.Experiments.Resilience, UrlFormat = DiagnosticIds.UrlFormat)]
+public class ResilienceHandler : DelegatingHandler
 {
  private readonly Func<HttpRequestMessage, ResiliencePipeline<HttpResponseMessage>> _pipelineProvider;
 
+ /// <summary>
+ /// Initializes a new instance of the <see cref="ResilienceHandler"/> class.
+ /// </summary>
+ /// <param name="pipelineProvider">The pipeline provider that supplies pipelines in response to an http message.</param>
+ /// <exception cref="ArgumentNullException">If <paramref name="pipelineProvider"/> is <see langword="null"/>.</exception>
  public ResilienceHandler(Func<HttpRequestMessage, ResiliencePipeline<HttpResponseMessage>> pipelineProvider)
  {
- _pipelineProvider = pipelineProvider;
+ _pipelineProvider = Throw.IfNull(pipelineProvider);
  }
 
- /// <inheritdoc/>
+ /// <summary>
+ /// Initializes a new instance of the <see cref="ResilienceHandler"/> class.
+ /// </summary>
+ /// <param name="pipeline">The pipeline to use for the message.</param>
+ /// <exception cref="ArgumentNullException">If <paramref name="pipeline"/> is <see langword="null"/>.</exception>
+ public ResilienceHandler(ResiliencePipeline<HttpResponseMessage> pipeline)
+ {
+ _ = Throw.IfNull(pipeline);
+ _pipelineProvider = _ => pipeline;
+ }
+
+ /// <summary>
+ /// Sends an HTTP request to the inner handler to send to the server as an asynchronous operation.
+ /// </summary>
+ /// <param name="request">The HTTP request message to send to the server.</param>
+ /// <param name="cancellationToken">A cancellation token to cancel operation.</param>
+ /// <returns>The task object representing the asynchronous operation.</returns>
+ /// <exception cref="ArgumentNullException">If <paramref name="request"/> is <see langword="null"/>.</exception>
  protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
  {
+ _ = Throw.IfNull(request);
+
  var pipeline = _pipelineProvider(request);
  var created = false;
  if (request.GetResilienceContext() is not ResilienceContext context)

test/Libraries/Microsoft.Extensions.Http.Resilience.Tests/Resilience/ResilienceHandlerTest.cs

@@ -22,7 +22,7 @@ public class ResilienceHandlerTest
  [Theory]
  public async Task SendAsync_EnsureRequestMetadataFlows(bool resilienceContextSet)
  {
- using var handler = new ResilienceHandler(_ => ResiliencePipeline<HttpResponseMessage>.Empty);
+ using var handler = new ResilienceHandler(ResiliencePipeline<HttpResponseMessage>.Empty);
  using var invoker = new HttpMessageInvoker(handler);
  using var request = new HttpRequestMessage();