Fix CA1062 warning (#2222)

Fix warnings in `RateLimitPolicy`.

Author: Zombach

src/Polly/RateLimit/RateLimitPolicy.cs

@@ -4,7 +4,6 @@ namespace Polly.RateLimit;
 /// <summary>
 /// A rate-limit policy that can be applied to synchronous delegates.
 /// </summary>
-#pragma warning disable CA1062 // Validate arguments of public methods
 public class RateLimitPolicy : Policy, IRateLimitPolicy
 {
     private readonly IRateLimiter _rateLimiter;
@@ -14,8 +13,15 @@ internal RateLimitPolicy(IRateLimiter rateLimiter) =>
 
     /// <inheritdoc/>
     [DebuggerStepThrough]
-    protected override TResult Implementation<TResult>(Func<Context, CancellationToken, TResult> action, Context context, CancellationToken cancellationToken) =>
-        RateLimitEngine.Implementation(_rateLimiter, null, action, context, cancellationToken);
+    protected override TResult Implementation<TResult>(Func<Context, CancellationToken, TResult> action, Context context, CancellationToken cancellationToken)
+    {
+        if (action is null)
+        {
+            throw new ArgumentNullException(nameof(action));
+        }
+
+        return RateLimitEngine.Implementation(_rateLimiter, null, action, context, cancellationToken);
+    }
 }
 
 /// <summary>
@@ -37,6 +43,13 @@ internal RateLimitPolicy(
 
     /// <inheritdoc/>
     [DebuggerStepThrough]
-    protected override TResult Implementation(Func<Context, CancellationToken, TResult> action, Context context, CancellationToken cancellationToken) =>
-        RateLimitEngine.Implementation(_rateLimiter, _retryAfterFactory, action, context, cancellationToken);
+    protected override TResult Implementation(Func<Context, CancellationToken, TResult> action, Context context, CancellationToken cancellationToken)
+    {
+        if (action is null)
+        {
+            throw new ArgumentNullException(nameof(action));
+        }
+
+        return RateLimitEngine.Implementation(_rateLimiter, _retryAfterFactory, action, context, cancellationToken);
+    }
 }

test/Polly.Specs/RateLimit/RateLimitPolicySpecs.cs

@@ -31,4 +31,30 @@ protected override (bool, TimeSpan) TryExecuteThroughPolicy(IRateLimitPolicy pol
             throw new InvalidOperationException("Unexpected policy type in test construction.");
         }
     }
+
+    [Fact]
+    public void Should_throw_when_action_is_null()
+    {
+        var flags = BindingFlags.NonPublic | BindingFlags.Instance;
+        Func<Context, CancellationToken, EmptyStruct> action = null!;
+        IRateLimiter rateLimiter = RateLimiterFactory.Create(TimeSpan.FromSeconds(1), 1);
+
+        var instance = Activator.CreateInstance(
+            typeof(RateLimitPolicy),
+            flags,
+            null,
+            [rateLimiter],
+            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");
+    }
 }

test/Polly.Specs/RateLimit/RateLimitPolicyTResultSpecs.cs

@@ -47,4 +47,30 @@ protected override TResult TryExecuteThroughPolicy<TResult>(IRateLimitPolicy<TRe
             throw new InvalidOperationException("Unexpected policy type in test construction.");
         }
     }
+
+    [Fact]
+    public void Should_throw_when_action_is_null()
+    {
+        var flags = BindingFlags.NonPublic | BindingFlags.Instance;
+        Func<Context, CancellationToken, EmptyStruct> action = null!;
+        IRateLimiter rateLimiter = RateLimiterFactory.Create(TimeSpan.FromSeconds(1), 1);
+        Func<TimeSpan, Context, EmptyStruct>? retryAfterFactory = null;
+
+        var instance = Activator.CreateInstance(
+            typeof(RateLimitPolicy<EmptyStruct>),
+            flags,
+            null,
+            [rateLimiter, retryAfterFactory],
+            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");
+    }
 }