Ensure ColletionIndex placeholder can be accessed in child validators.

Changelog.txt

@@ -23,6 +23,7 @@ FluentValidationModelValidatorProvider and FluentValidationModelValidator are no
 Add additional overload of SetValidator that takes a Func that receives the current property value.
 Work around a bug in ASP.NET Core's integration testing components that can cause ConfigureServices to run multiple times.
 SourceLink integration.
+{CollectionIndex} placeholder can now be accessed in child validators.
 
 8.6.2 - 29 February 2020
 Fix CollectionIndex placeholder not working with async workflow.

src/FluentValidation.Tests/ForEachRuleTests.cs

@@ -529,6 +529,70 @@ public AppropriatenessAnswerViewModelRequiredValidator()
 			result.IsValid.ShouldBeFalse();
 		}
 
+		[Fact]
+		public void Can_access_parent_index() {
+			var personValidator = new InlineValidator<Person>();
+			var orderValidator = new InlineValidator<Order>();
+
+			orderValidator.RuleFor(order => order.ProductName)
+				.NotEmpty()
+				.WithMessage("{CollectionIndex} must not be empty");
+
+			// Two rules - one for each collection syntax.
+
+			personValidator.RuleFor(x => x.Orders)
+				.NotEmpty()
+				.ForEach(order => {
+					order.SetValidator(orderValidator);
+				});
+
+			personValidator.RuleForEach(x => x.Orders).SetValidator(orderValidator);
+
+			var result = personValidator.Validate(new Person() {
+				Orders = new List<Order> {
+					new Order() { ProductName =  "foo"},
+					new Order(),
+					new Order() { ProductName = "bar" }
+				}
+			});
+
+			result.IsValid.ShouldBeFalse();
+			result.Errors[0].ErrorMessage.ShouldEqual("1 must not be empty");
+			result.Errors[0].ErrorMessage.ShouldEqual("1 must not be empty");
+		}
+
+		[Fact]
+		public async Task Can_access_parent_index_async() {
+			var personValidator = new InlineValidator<Person>();
+			var orderValidator = new InlineValidator<Order>();
+
+			orderValidator.RuleFor(order => order.ProductName)
+				.NotEmpty()
+				.WithMessage("{CollectionIndex} must not be empty");
+
+			// Two rules - one for each collection syntax.
+
+			personValidator.RuleFor(x => x.Orders)
+				.NotEmpty()
+				.ForEach(order => {
+					order.SetValidator(orderValidator);
+				});
+
+			personValidator.RuleForEach(x => x.Orders).SetValidator(orderValidator);
+
+			var result = await personValidator.ValidateAsync(new Person() {
+				Orders = new List<Order> {
+					new Order() { ProductName =  "foo"},
+					new Order(),
+					new Order() { ProductName = "bar" }
+				}
+			});
+
+			result.IsValid.ShouldBeFalse();
+			result.Errors[0].ErrorMessage.ShouldEqual("1 must not be empty");
+			result.Errors[0].ErrorMessage.ShouldEqual("1 must not be empty");
+		}
+
 		public class OrderValidator : AbstractValidator<Order> {
 			public OrderValidator() {
 				RuleFor(x => x.ProductName).NotEmpty();

src/FluentValidation/FluentValidation.csproj

@@ -25,6 +25,7 @@ Changes in 9.0.0:
 * ASP.NET Core: FluentValidationModelValidatorProvider and FluentValidationModelValidator are now public.
 * Work around a bug in ASP.NET Core's integration testing components that can cause ConfigureServices to run multiple times.
 * SourceLink integration.
+* {CollectionIndex} placeholder can now be accessed in child validators.
 
 Full release notes can be found at https://github.com/FluentValidation/FluentValidation/blob/master/Changelog.txt
 FluentValidation 8 is a major release. Please read the upgrade notes at https://fluentvalidation.net/upgrading-to-8

src/FluentValidation/Internal/CollectionPropertyRule.cs

@@ -191,5 +191,6 @@ public class CollectionPropertyRule<TProperty> : PropertyRule {
 
 			return results;
 		}
+
 	}
 }

src/FluentValidation/Validators/ChildValidatorAdaptor.cs

@@ -40,7 +40,7 @@ public class ChildValidatorAdaptor : NoopPropertyValidator, IChildValidatorAdapt
 		public override IEnumerable<ValidationFailure> Validate(PropertyValidatorContext context) {
 			if (Options.Condition != null && !Options.Condition(context)) {
 				return Enumerable.Empty<ValidationFailure>();
-			} 
+			}
 
 			if (context.PropertyValue == null) {
 				return Enumerable.Empty<ValidationFailure>();
@@ -53,18 +53,29 @@ public class ChildValidatorAdaptor : NoopPropertyValidator, IChildValidatorAdapt
 			}
 
 			var newContext = CreateNewValidationContextForChildValidator(context.PropertyValue, context);
-			return validator.Validate(newContext).Errors;
+
+			// If we're inside a collection with RuleForEach, then preserve the CollectionIndex placeholder
+			// and pass it down to child validator by caching it in the RootContextData which flows through to
+			// the child validator. PropertyValidator.PrepareMessageFormatterForValidationError handles extracting this.
+			HandleCollectionIndex(context, out object originalIndex, out object currentIndex);
+
+			var results = validator.Validate(newContext).Errors;
+
+			// Reset the collection index
+			ResetCollectionIndex(context, originalIndex, currentIndex);
+
+			return results;
 		}
 
 		public override async Task<IEnumerable<ValidationFailure>> ValidateAsync(PropertyValidatorContext context, CancellationToken cancellation) {
 			if (Options.Condition != null && !Options.Condition(context)) {
 				return Enumerable.Empty<ValidationFailure>();
-			} 
-			
+			}
+
 			if (Options.AsyncCondition != null && !await Options.AsyncCondition(context, cancellation)) {
 				return Enumerable.Empty<ValidationFailure>();
 			}
-			
+
 			if (context.PropertyValue == null) {
 				return Enumerable.Empty<ValidationFailure>();
 			}
@@ -76,7 +87,16 @@ public class ChildValidatorAdaptor : NoopPropertyValidator, IChildValidatorAdapt
 			}
 
 			var newContext = CreateNewValidationContextForChildValidator(context.PropertyValue, context);
+
+			// If we're inside a collection with RuleForEach, then preserve the CollectionIndex placeholder
+			// and pass it down to child validator by caching it in the RootContextData which flows through to
+			// the child validator. PropertyValidator.PrepareMessageFormatterForValidationError handles extracting this.
+			HandleCollectionIndex(context, out object originalIndex, out object currentIndex);
+
 			var result = await validator.ValidateAsync(newContext, cancellation);
+
+			ResetCollectionIndex(context, originalIndex, currentIndex);
+
 			return result.Errors;
 		}
 
@@ -99,5 +119,25 @@ public class ChildValidatorAdaptor : NoopPropertyValidator, IChildValidatorAdapt
 		public override bool ShouldValidateAsynchronously(ValidationContext context) {
 			return context.IsAsync() || Options.AsyncCondition != null;
 		}
+
+		private void HandleCollectionIndex(PropertyValidatorContext context, out object originalIndex, out object index) {
+			originalIndex = null;
+			if (context.MessageFormatter.PlaceholderValues.TryGetValue("CollectionIndex", out index)) {
+				context.ParentContext.RootContextData.TryGetValue("__FV_CollectionIndex", out originalIndex);
+				context.ParentContext.RootContextData["__FV_CollectionIndex"] = index;
+			}
+		}
+
+		private void ResetCollectionIndex(PropertyValidatorContext context, object originalIndex, object index) {
+			// Reset the collection index
+			if (index != null) {
+				if (originalIndex != null) {
+					context.ParentContext.RootContextData["__FV_CollectionIndex"] = originalIndex;
+				}
+				else {
+					context.ParentContext.RootContextData.Remove("__FV_CollectionIndex");
+				}
+			}
+		}
 	}
-}
+}

src/FluentValidation/Validators/PropertyValidator.cs

@@ -82,6 +82,18 @@ public abstract class PropertyValidator : IPropertyValidator {
 		protected virtual void PrepareMessageFormatterForValidationError(PropertyValidatorContext context) {
 			context.MessageFormatter.AppendPropertyName(context.DisplayName);
 			context.MessageFormatter.AppendPropertyValue(context.PropertyValue);
+
+			// If there's a collection index cached in the root context data then add it
+			// to the message formatter. This happens when a child validator is executed
+			// as part of a call to RuleForEach. Usually parameters are not flowed through to
+			// child validators, but we make an exception for collection indices.
+			if (context.ParentContext.RootContextData.TryGetValue("__FV_CollectionIndex", out var index)) {
+				// If our property validator has explicitly added a placeholder for the collection index
+				// don't overwrite it with the cached version.
+				if (!context.MessageFormatter.PlaceholderValues.ContainsKey("CollectionIndex")) {
+					context.MessageFormatter.AppendArgument("CollectionIndex", index);
+				}
+			}
 		}
 
 		/// <summary>