Debugger proxies for resilience strategies (#1379)

src/Polly.Core/ResilienceStrategy.DebuggerProxy.cs

@@ -0,0 +1,35 @@
+namespace Polly;
+
+public abstract partial class ResilienceStrategy
+{
+    internal sealed class DebuggerProxy
+    {
+        private readonly ResilienceStrategy _resilienceStrategy;
+
+        public DebuggerProxy(ResilienceStrategy resilienceStrategy) => _resilienceStrategy = resilienceStrategy;
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public IEnumerable<ResilienceStrategy> Strategies => UnwrapStrategies(_resilienceStrategy);
+
+        private IEnumerable<ResilienceStrategy> UnwrapStrategies(ResilienceStrategy strategy)
+        {
+            if (strategy is ResilienceStrategyPipeline pipeline)
+            {
+                return pipeline.Strategies;
+            }
+
+            if (strategy is ReloadableResilienceStrategy reloadableResilienceStrategy)
+            {
+                var list = new List<ResilienceStrategy>
+                {
+                    strategy
+                };
+                list.AddRange(UnwrapStrategies(reloadableResilienceStrategy.Strategy));
+
+                return list;
+            }
+
+            return new[] { strategy };
+        }
+    }
+}

src/Polly.Core/ResilienceStrategy.TResult.Async.cs

@@ -1,3 +1,5 @@
+using Polly.Utils;
+
 namespace Polly;
 
 /// <summary>
@@ -8,6 +10,7 @@ namespace Polly;
 /// Resilience strategy supports various types of callbacks of <typeparamref name="TResult"/> result type
 /// and provides a unified way to execute them. This includes overloads for synchronous and asynchronous callbacks.
 /// </remarks>
+[DebuggerTypeProxy(typeof(ResilienceStrategy<>.DebuggerProxy))]
 public partial class ResilienceStrategy<TResult>
 {
     internal ResilienceStrategy(ResilienceStrategy strategy) => Strategy = strategy;

src/Polly.Core/ResilienceStrategy.TResult.DebuggerProxy.cs

@@ -0,0 +1,14 @@
+namespace Polly;
+
+public partial class ResilienceStrategy<TResult>
+{
+    internal sealed class DebuggerProxy
+    {
+        private readonly ResilienceStrategy.DebuggerProxy _proxy;
+
+        public DebuggerProxy(ResilienceStrategy<TResult> strategy) => _proxy = new ResilienceStrategy.DebuggerProxy(strategy.Strategy);
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public IEnumerable<ResilienceStrategy> Strategies => _proxy.Strategies;
+    }
+}

src/Polly.Core/ResilienceStrategy.cs

@@ -9,6 +9,7 @@ namespace Polly;
 /// Resilience strategy supports various types of callbacks and provides a unified way to execute them.
 /// This includes overloads for synchronous and asynchronous callbacks, generic and non-generic callbacks.
 /// </remarks>
+[DebuggerTypeProxy(typeof(DebuggerProxy))]
 public abstract partial class ResilienceStrategy
 {
     /// <summary>

src/Polly.Core/Utils/ResilienceStrategyPipeline.cs

@@ -1,10 +1,13 @@
+using System.Diagnostics;
+
 namespace Polly.Utils;
 
 #pragma warning disable S2302 // "nameof" should be used
 
 /// <summary>
 /// A pipeline of strategies.
 /// </summary>
+[DebuggerDisplay("ResilienceStrategyPipeline, Strategies = {Strategies.Count}")]
 internal sealed class ResilienceStrategyPipeline : ResilienceStrategy
 {
     private readonly ResilienceStrategy _pipeline;

test/Polly.Core.Tests/ResilienceStrategyTests.cs

@@ -1,3 +1,6 @@
+using Moq;
+using Polly.Utils;
+
 namespace Polly.Core.Tests;
 
 public partial class ResilienceStrategyTests
@@ -28,6 +31,22 @@ await TestUtilities.AssertWithTimeoutAsync(async () =>
         });
     }
 
+    [Fact]
+    public void DebuggerProxy_Ok()
+    {
+        var pipeline = ResilienceStrategyPipeline.CreatePipeline(new[]
+        {
+            new TestResilienceStrategy(),
+            new TestResilienceStrategy()
+        });
+        var reloadable = new ReloadableResilienceStrategy(pipeline, () => default, () => pipeline, TestUtilities.CreateResilienceTelemetry(Mock.Of<DiagnosticSource>()));
+
+        new ResilienceStrategy.DebuggerProxy(NullResilienceStrategy.Instance).Strategies.Should().HaveCount(1);
+        new ResilienceStrategy.DebuggerProxy(pipeline).Strategies.Should().HaveCount(2);
+        new ResilienceStrategy.DebuggerProxy(reloadable).Strategies.Should().HaveCount(3);
+        new ResilienceStrategy<string>.DebuggerProxy(NullResilienceStrategy<string>.Instance).Strategies.Should().HaveCount(1);
+    }
+
     public class ExecuteParameters<T> : ExecuteParameters
     {
         public ExecuteParameters(Func<ResilienceStrategy, Task<T>> execute, T resultValue)