Prevent duplicate validation of implemented interfaces (#109)

src/Immediate.Validations.Generators/Templates/Validations.sbntxt

@@ -16,9 +16,15 @@ partial {{ c.type }} {{ c.name }}
 partial {{ class.type }} {{ class.name }}
 {
 	static ValidationResult IValidationTarget<{{ class.name }}>.Validate({{ class.name; if is_reference_type; "?"; end }} target) =>
-		Validate(target);
+		Validate(target, []);
 
-	public static {{ if class.type == "interface"; "new"; end }} ValidationResult Validate({{ class.name; if is_reference_type; "?"; end }} target)
+	static ValidationResult IValidationTarget<{{ class.name }}>.Validate({{ class.name; if is_reference_type; "?"; end }} target, ValidationResult errors) =>
+		Validate(target, errors);
+
+	public static {{ if class.type == "interface"; "new"; end }} ValidationResult Validate({{ class.name; if is_reference_type; "?"; end }} target) =>
+		Validate(target, []);
+
+	public static {{ if class.type == "interface"; "new"; end }} ValidationResult Validate({{ class.name; if is_reference_type; "?"; end }} target, ValidationResult errors)
 	{
 		{{~ if is_reference_type ~}}
 		if (target is not { } t)
@@ -31,11 +37,12 @@ partial {{ class.type }} {{ class.name }}
 		{{~ else ~}}
 		var t = target;
 		{{~ end ~}}
-
-		var errors = new ValidationResult();
 
+		if (!errors.VisitType(typeof({{ class.name }})))
+			return errors;
+
 		{{~ for bc in base_validation_targets ~}}
-		errors.AddRange({{ bc }}.Validate(t));
+		{{ bc }}.Validate(t, errors);
 		{{~ end ~}}
 
 		{{~ if !skip_self ~}}

src/Immediate.Validations.Shared/IValidationTarget.cs

@@ -25,4 +25,23 @@ public interface IValidationTarget<T>
 		Justification = "This is a static method to validate an instance of the self type."
 	)]
 	static abstract ValidationResult Validate(T? target);
+
+	/// <summary>
+	///	    A method which can be used to validate instances of the type <typeparamref name="T"/>.
+	/// </summary>
+	/// <param name="target">
+	///	    An instance of type <typeparamref name="T"/> which should be validated.
+	/// </param>
+	/// <param name="errors">
+	///		The operating <see cref="ValidationResult" /> to add validation entries to.
+	/// </param>
+	/// <returns>
+	///	    The parameter <paramref name="errors"/>, for easier consumption.
+	/// </returns>
+	[SuppressMessage(
+		"Design",
+		"CA1000:Do not declare static members on generic types",
+		Justification = "This is a static method to validate an instance of the self type."
+	)]
+	static abstract ValidationResult Validate(T? target, ValidationResult errors);
 }

src/Immediate.Validations.Shared/ValidationResult.cs

@@ -1,6 +1,7 @@
 using System.Collections;
 using System.ComponentModel;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq.Expressions;
 using System.Reflection;
 using System.Text.RegularExpressions;
@@ -16,6 +17,18 @@ public sealed partial class ValidationResult : IEnumerable<ValidationError>
 	private static partial Regex FormatRegex();
 
 	private List<ValidationError>? _errors;
+	private HashSet<string>? _types;
+
+	/// <summary>
+	///		Internal function used to support tracking which types have been visited as part of validation.
+	/// </summary>
+	/// <remarks>
+	///		Should not be used by consumers.
+	/// </remarks>
+	[EditorBrowsable(EditorBrowsableState.Never)]
+	[SuppressMessage("Design", "CA1062:Validate arguments of public methods")]
+	public bool VisitType(Type type) =>
+		(_types ??= []).Add(type.ToString());
 
 	/// <summary>
 	///		Indicates whether the validation was successful.

tests/Immediate.Validations.FunctionalTests/IntegrationTests/DuplicateTypeVisitTests.cs

@@ -0,0 +1,34 @@
+using Immediate.Validations.Shared;
+using Xunit;
+
+namespace Immediate.Validations.FunctionalTests.IntegrationTests;
+
+public partial class DuplicateTypeVisitTests
+{
+	[Validate]
+	public partial interface IBaseInterface : IValidationTarget<IBaseInterface>
+	{
+		public static int VisitCount { get; set; }
+
+		private static void AdditionalValidations(ValidationResult _, IBaseInterface __)
+		{
+			VisitCount++;
+		}
+	}
+
+	[Validate]
+	public partial interface ISubInterface : IBaseInterface, IValidationTarget<ISubInterface>;
+
+	[Validate]
+	public sealed partial record ValidateRecord : IBaseInterface, ISubInterface, IValidationTarget<ValidateRecord>;
+
+	[Fact]
+	public void TypeValidatorsAreVisitedAtMostOnce()
+	{
+		var record = new ValidateRecord();
+
+		_ = ValidateRecord.Validate(record);
+
+		Assert.Equal(1, IBaseInterface.VisitCount);
+	}
+}

tests/Immediate.Validations.Tests/AnalyzerTests/AnalyzerTestHelpers.cs

@@ -1,5 +1,6 @@
 using System.Collections.Immutable;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Testing;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -10,7 +11,7 @@ namespace Immediate.Validations.Tests.AnalyzerTests;
 public static class AnalyzerTestHelpers
 {
 	public static CSharpAnalyzerTest<TAnalyzer, DefaultVerifier> CreateAnalyzerTest<TAnalyzer>(
-		string inputSource
+		[StringSyntax("c#-test")] string inputSource
 	)
 		where TAnalyzer : DiagnosticAnalyzer, new()
 	{
@@ -105,7 +106,7 @@ params DiagnosticResult[] diagnostics
 	}
 
 	public static CSharpSuppressorTest<TSuppressor, DefaultVerifier> CreateSuppressorTest<TSuppressor>(
-		string inputSource
+		[StringSyntax("c#-test")] string inputSource
 	)
 		where TSuppressor : DiagnosticSuppressor, new()
 	{
@@ -128,7 +129,7 @@ string inputSource
 	}
 
 	public static CSharpSuppressorTest<TSuppressor, DefaultVerifier> CreateSuppressorTest<TSuppressor, TAnalyzer>(
-		string inputSource
+		[StringSyntax("c#-test")] string inputSource
 	)
 		where TSuppressor : DiagnosticSuppressor, new()
 		where TAnalyzer : DiagnosticAnalyzer, new()