Fix warning CA1062#RetryPolicy

src/Polly/Retry/RetryPolicy.cs

@@ -4,7 +4,6 @@ namespace Polly.Retry;
 /// <summary>
 /// A retry policy that can be applied to synchronous delegates.
 /// </summary>
-#pragma warning disable CA1062 // Validate arguments of public methods
 public class RetryPolicy : Policy, IRetryPolicy
 {
     private readonly Action<Exception, TimeSpan, int, Context> _onRetry;
@@ -29,6 +28,11 @@ internal RetryPolicy(
     /// <inheritdoc/>
     protected override TResult Implementation<TResult>(Func<Context, CancellationToken, TResult> action, Context context, CancellationToken cancellationToken)
     {
+        if (action is null)
+        {
+            throw new ArgumentNullException(nameof(action));
+        }
+
         var sleepDurationProvider = _sleepDurationProvider != null
             ? (retryCount, outcome, ctx) => _sleepDurationProvider(retryCount, outcome.Exception, ctx)
             : (Func<int, DelegateResult<TResult>, Context, TimeSpan>?)null;
@@ -72,8 +76,14 @@ internal RetryPolicy(
 
     /// <inheritdoc/>
     [DebuggerStepThrough]
-    protected override TResult Implementation(Func<Context, CancellationToken, TResult> action, Context context, CancellationToken cancellationToken) =>
-        RetryEngine.Implementation(
+    protected override TResult Implementation(Func<Context, CancellationToken, TResult> action, Context context, CancellationToken cancellationToken)
+    {
+        if (action is null)
+        {
+            throw new ArgumentNullException(nameof(action));
+        }
+
+        return RetryEngine.Implementation(
             action,
             context,
             ExceptionPredicates,
@@ -83,4 +93,5 @@ protected override TResult Implementation(Func<Context, CancellationToken, TResu
             _permittedRetryCount,
             _sleepDurationsEnumerable,
             _sleepDurationProvider);
+    }
 }

test/Polly.Specs/Retry/RetrySpecs.cs

@@ -2,6 +2,36 @@
 
 public class RetrySpecs
 {
+    [Fact]
+    public void Should_throw_when_action_is_null()
+    {
+        var flags = BindingFlags.NonPublic | BindingFlags.Instance;
+        Func<Context, CancellationToken, EmptyStruct> action = null!;
+        var policyBuilder = new PolicyBuilder(exception => exception);
+        Action<Exception, TimeSpan, int, Context> onRetry = (_, _, _, _) => { };
+        int permittedRetryCount = int.MaxValue;
+        IEnumerable<TimeSpan>? sleepDurationsEnumerable = null;
+        Func<int, Exception, Context, TimeSpan>? sleepDurationProvider = null;
+
+        var instance = Activator.CreateInstance(
+            typeof(RetryPolicy),
+            flags,
+            null,
+            [policyBuilder, onRetry, permittedRetryCount, sleepDurationsEnumerable, sleepDurationProvider],
+            null)!;
+        var instanceType = instance.GetType();
+        var methods = instanceType.GetMethods(flags);
+        var methodInfo = methods.First(method => method is { Name: "Implementation", ReturnType.Name: "TResult" });
+        var generic = methodInfo.MakeGenericMethod(typeof(EmptyStruct));
+
+        var func = () => generic.Invoke(instance, [action, new Context(), CancellationToken.None]);
+
+        var exceptionAssertions = func.Should().Throw<TargetInvocationException>();
+        exceptionAssertions.And.Message.Should().Be("Exception has been thrown by the target of an invocation.");
+        exceptionAssertions.And.InnerException.Should().BeOfType<ArgumentNullException>()
+            .Which.ParamName.Should().Be("action");
+    }
+
     [Fact]
     public void Should_throw_when_retry_count_is_less_than_zero_without_context()
     {

test/Polly.Specs/Retry/RetryTResultSpecs.cs

@@ -4,6 +4,35 @@ namespace Polly.Specs.Retry;
 
 public class RetryTResultSpecs
 {
+    [Fact]
+    public void Should_throw_when_action_is_null()
+    {
+        var flags = BindingFlags.NonPublic | BindingFlags.Instance;
+        Func<Context, CancellationToken, EmptyStruct> action = null!;
+        var policyBuilder = new PolicyBuilder<EmptyStruct>(exception => exception);
+        Action<DelegateResult<EmptyStruct>, TimeSpan, int, Context> onRetry = (_, _, _, _) => { };
+        int permittedRetryCount = int.MaxValue;
+        IEnumerable<TimeSpan>? sleepDurationsEnumerable = null;
+        Func<int, DelegateResult<EmptyStruct>, Context, TimeSpan>? sleepDurationProvider = null;
+
+        var instance = Activator.CreateInstance(
+            typeof(RetryPolicy<EmptyStruct>),
+            flags,
+            null,
+            [policyBuilder, onRetry, permittedRetryCount, sleepDurationsEnumerable, sleepDurationProvider],
+            null)!;
+        var instanceType = instance.GetType();
+        var methods = instanceType.GetMethods(flags);
+        var methodInfo = methods.First(method => method is { Name: "Implementation", ReturnType.Name: "EmptyStruct" });
+
+        var func = () => methodInfo.Invoke(instance, [action, new Context(), CancellationToken.None]);
+
+        var exceptionAssertions = func.Should().Throw<TargetInvocationException>();
+        exceptionAssertions.And.Message.Should().Be("Exception has been thrown by the target of an invocation.");
+        exceptionAssertions.And.InnerException.Should().BeOfType<ArgumentNullException>()
+            .Which.ParamName.Should().Be("action");
+    }
+
     [Fact]
     public void Should_throw_when_retry_count_is_less_than_zero_without_context()
     {