Add OnFailureCreated callback

src/FluentValidation.Tests/OnFailureHookTester.cs

@@ -0,0 +1,43 @@
+#region License
+// Copyright (c) .NET Foundation and contributors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// The latest version of this file can be found at https://github.com/FluentValidation/FluentValidation
+#endregion
+
+namespace FluentValidation.Tests;
+
+using Xunit;
+
+public class OnFailureHookTester {
+
+	[Fact]
+	public void Runs_hook_when_failure_created() {
+		try {
+			ValidatorOptions.Global.OnFailureCreated = (failure, context, propertyValue, rule, component) => {
+				failure.PropertyName = "Foo";
+				return failure;
+			};
+
+			var validator = new InlineValidator<Person>();
+			validator.RuleFor(x => x.Surname).NotNull();
+			var result = validator.Validate(new Person());
+			result.Errors[0].PropertyName.ShouldEqual("Foo");
+		}
+		finally {
+			ValidatorOptions.Global.OnFailureCreated = null;
+		}
+
+	}
+}

src/FluentValidation/Internal/RuleBase.cs

@@ -325,6 +325,10 @@ public string GetDisplayName(ValidationContext<T> context)
 			failure.CustomState = component.CustomStateProvider(context, value);
 		}
 
+		if (ValidatorOptions.Global.OnFailureCreated != null) {
+			failure = ValidatorOptions.Global.OnFailureCreated(failure, context, value, this, component);
+		}
+
 		return failure;
 	}
 }

src/FluentValidation/ValidatorOptions.cs

@@ -20,10 +20,12 @@ namespace FluentValidation;
 
 using System;
 using System.Collections.Generic;
+using System.Data;
 using System.Linq.Expressions;
 using System.Reflection;
 using Internal;
 using Resources;
+using Results;
 using Validators;
 
 /// <summary>
@@ -198,6 +200,11 @@ public class ValidatorConfiguration {
 		set => _errorCodeResolver = value ?? DefaultErrorCodeResolver;
 	}
 
+	/// <summary>
+	/// Defines a hook that runs when a <see cref="ValidationFailure"/> is created.
+	/// </summary>
+	public Func<ValidationFailure, IValidationContext, object, IValidationRule, IRuleComponent, ValidationFailure> OnFailureCreated { get; set; }
+
 	static string DefaultPropertyNameResolver(Type type, MemberInfo memberInfo, LambdaExpression expression) {
 		if (expression != null) {
 			var chain = PropertyChain.FromExpression(expression);