From 2255cd3c14cb8993e5dd426a224da30b61b47e22 Mon Sep 17 00:00:00 2001
From: iancooper <ian_hammond_cooper@yahoo.co.uk>
Date: Sat, 26 Sep 2026 23:05:08 +0100
Subject: [PATCH] Port App-vNext/Polly@482bdf82: return null from
 FaultGenerator when no fault is generated

The implicit conversion from FaultGenerator to the FaultGenerator delegate
dereferenced the generated outcome unconditionally, so a generator with no
exceptions registered, or with every weight at zero, threw
InvalidOperationException instead of returning null (no fault).

Upstream: App-vNext/Polly#3220. Refs #28.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
---
 .../Simmy/Fault/FaultGenerator.cs             |  2 +-
 .../Simmy/Fault/FaultGeneratorTests.cs        | 27 +++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/Paramore.Fences.Core/Simmy/Fault/FaultGenerator.cs b/src/Paramore.Fences.Core/Simmy/Fault/FaultGenerator.cs
index c7686900..5901f8f1 100644
--- a/src/Paramore.Fences.Core/Simmy/Fault/FaultGenerator.cs
+++ b/src/Paramore.Fences.Core/Simmy/Fault/FaultGenerator.cs
@@ -78,6 +78,6 @@ public FaultGenerator AddException<TException>(int weight = DefaultWeight)
 
         var generatorDelegate = generator._helper.CreateGenerator();
 
-        return args => new ValueTask<Exception?>(generatorDelegate(args.Context)!.Value.Exception);
+        return args => new ValueTask<Exception?>(generatorDelegate(args.Context)?.Exception);
     }
 }
diff --git a/test/Paramore.Fences.Core.Tests/Simmy/Fault/FaultGeneratorTests.cs b/test/Paramore.Fences.Core.Tests/Simmy/Fault/FaultGeneratorTests.cs
index ba98c44b..c9e8b852 100644
--- a/test/Paramore.Fences.Core.Tests/Simmy/Fault/FaultGeneratorTests.cs
+++ b/test/Paramore.Fences.Core.Tests/Simmy/Fault/FaultGeneratorTests.cs
@@ -39,6 +39,33 @@ public void AddException_FactoryWithResilienceContext_Ok()
         Generate(generator).ShouldBeOfType<InvalidOperationException>();
     }
 
+    [Fact]
+    public void ImplicitConversion_NoExceptionRegistered_ReturnsNull()
+    {
+        // Arrange
+        var generator = new FaultGenerator();
+
+        // Act
+        var fault = Generate(generator);
+
+        // Assert
+        fault.ShouldBeNull();
+    }
+
+    [Fact]
+    public void ImplicitConversion_AllWeightsZero_ReturnsNull()
+    {
+        // Arrange
+        var generator = new FaultGenerator();
+        generator.AddException<InvalidOperationException>(weight: 0);
+
+        // Act
+        var fault = Generate(generator);
+
+        // Assert
+        fault.ShouldBeNull();
+    }
+
     private static Exception? Generate(FaultGenerator generator)
     {
         Func<FaultGeneratorArguments, ValueTask<Exception?>> func = generator;