Add support for dependent rules for custom rules #2170

Changelog.txt

@@ -3,6 +3,7 @@ Fix memory leak in NotEmptyValidator/EmptyValidator (#2174)
 Add more descriptive error messages if a rule throws a NullReferenceException (#2152)
 Add support for caching root parameter expressions (eg RuleFor(x => x)) (#2168)
 Add builds for .net 8
+Add support for dependent rules for custom rules (#2170)
 
 11.8.1 - 22 Nov 2023
 Fix unintentional behavioural changes in introduced in the previous release as part of #2158

src/FluentValidation.Tests/RuleDependencyTests.cs

@@ -38,8 +38,7 @@ public class RuleDependencyTests {
 	}
 
 	[Fact]
-	public void Does_not_invoke_dependent_rule_if_parent_rule_does_not_pass()
-	{
+	public void Does_not_invoke_dependent_rule_if_parent_rule_does_not_pass() {
 		var validator = new TestValidator();
 		validator.RuleFor(x => x.Surname).NotNull()
 			.DependentRules(() =>
@@ -253,8 +252,7 @@ public void Nested_dependent_rules_inside_ruleset_no_result_when_second_level_fa
 
 
 	[Fact]
-	public void Nested_dependent_rules_inside_ruleset_inside_method()
-	{
+	public void Nested_dependent_rules_inside_ruleset_inside_method() {
 		var validator = new TestValidator();
 		validator.RuleSet("MyRuleSet", () =>
 		{
@@ -277,8 +275,36 @@ public void Nested_dependent_rules_inside_ruleset_inside_method()
 		results.Errors.Single().PropertyName.ShouldEqual("Address");
 	}
 
-	private void BaseValidation(InlineValidator<Person> validator)
-	{
+	[Fact]
+	public void Invokes_dependent_rule_if_parent_custom_rule_passes() {
+		var validator = new TestValidator();
+		validator.RuleFor(x => x.Surname).Custom((name, context) => { })
+			.DependentRules(() => {
+				validator.RuleFor(x => x.Forename).NotNull();
+			});
+
+		var results = validator.Validate(new Person {Surname = "foo"});
+		results.Errors.Count.ShouldEqual(1);
+		results.Errors.Single().PropertyName.ShouldEqual("Forename");
+	}
+
+	[Fact]
+	public void Does_not_invoke_dependent_rule_if_parent_custom_rule_does_not_pass() {
+		var validator = new TestValidator();
+		validator.RuleFor(x => x.Surname).Custom((name, context) => {
+				context.AddFailure("Failed");
+			})
+			.DependentRules(() =>
+			{
+				validator.RuleFor(x => x.Forename).NotNull();
+			});
+
+		var results = validator.Validate(new Person { Surname = null });
+		results.Errors.Count.ShouldEqual(1);
+		results.Errors.Single().PropertyName.ShouldEqual("Surname");
+	}
+
+	private void BaseValidation(InlineValidator<Person> validator) {
 		validator.RuleFor(x => x.Address).NotNull();
 	}
 

src/FluentValidation/Internal/RuleBuilder.cs

@@ -94,6 +94,16 @@ internal class RuleBuilder<T, TProperty> : IRuleBuilderOptions<T, TProperty>, IR
 	}
 
 	IRuleBuilderOptions<T, TProperty> IRuleBuilderOptions<T, TProperty>.DependentRules(Action action) {
+		DependentRulesInternal(action);
+		return this;
+	}
+
+	IRuleBuilderOptionsConditions<T, TProperty> IRuleBuilderOptionsConditions<T, TProperty>.DependentRules(Action action) {
+		DependentRulesInternal(action);
+		return this;
+	}
+
+	private void DependentRulesInternal(Action action) {
 		var dependencyContainer = new List<IValidationRuleInternal<T>>();
 		// Capture any rules added to the parent validator inside this delegate.
 		using (ParentValidator.Rules.Capture(dependencyContainer.Add)) {
@@ -109,10 +119,10 @@ internal class RuleBuilder<T, TProperty> : IRuleBuilderOptions<T, TProperty>, IR
 		}
 
 		Rule.AddDependentRules(dependencyContainer);
-		return this;
 	}
 
 	public void AddComponent(RuleComponent<T,TProperty> component) {
 		Rule.Components.Add(component);
 	}
+
 }

src/FluentValidation/Syntax.cs

@@ -92,6 +92,10 @@ public interface IRuleBuilderOptions<T, out TProperty> : IRuleBuilder<T, TProper
 /// <typeparam name="T"></typeparam>
 /// <typeparam name="TProperty"></typeparam>
 public interface IRuleBuilderOptionsConditions<T, out TProperty> : IRuleBuilder<T, TProperty> {
+	/// <summary>
+	/// Creates a scope for declaring dependent rules.
+	/// </summary>
+	IRuleBuilderOptionsConditions<T, TProperty> DependentRules(Action action);
 }
 
 /// <summary>