fix: json deserialization issue of ValidationResult

src/FluentValidation.Tests/JsonSerializationTests.cs

@@ -0,0 +1,33 @@
+namespace FluentValidation.Tests {
+	using System.Text.Json;
+	using Results;
+	using Xunit;
+
+	public class JsonSerializationTests {
+		[Fact]
+		public void Consecutive_Serialize_Deserialization() {
+			var validationResult = new ValidationResult {
+				Errors = {
+					new ValidationFailure("MyProperty1", "Invalid MyProperty1"),
+					new ValidationFailure("MyProperty2", "Invalid MyProperty2"),
+					new ValidationFailure("MyProperty3", "Invalid MyProperty3")
+				}
+			};
+			// System.Text.Json
+			var serialized1 = JsonSerializer.Serialize(validationResult);
+			var deserialized1 = JsonSerializer.Deserialize<ValidationResult>(serialized1);
+
+			// Newtonsoft.Json
+			var serialized2 = Newtonsoft.Json.JsonConvert.SerializeObject(validationResult);
+			var deserialized2 = Newtonsoft.Json.JsonConvert.DeserializeObject<ValidationResult>(serialized2);
+
+			Assert.NotNull(deserialized1);
+			Assert.Equal(deserialized1.IsValid, deserialized2.IsValid);
+			Assert.Equal(deserialized1.Errors.Count, deserialized2.Errors.Count);
+			for (var i = 0; i < deserialized1.Errors.Count; i++) {
+				Assert.Equal(deserialized1.Errors[i].PropertyName, deserialized2.Errors[i].PropertyName);
+				Assert.Equal(deserialized1.Errors[i].ErrorMessage, deserialized2.Errors[i].ErrorMessage);
+			}
+		}
+	}
+}

src/FluentValidation/FluentValidation.csproj

@@ -24,5 +24,6 @@ Full release notes can be found at https://github.com/FluentValidation/FluentVal
   <ItemGroup>
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0" PrivateAssets="All" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All" />
+    <PackageReference Include="System.Text.Json" Version="6.0.3" />
   </ItemGroup>
 </Project>

src/FluentValidation/Results/ValidationFailure.cs

@@ -19,6 +19,7 @@
 namespace FluentValidation.Results {
 	using System;
 	using System.Collections.Generic;
+	using System.Text.Json.Serialization;
 
 	/// <summary>
 	/// Defines a validation failure
@@ -38,6 +39,7 @@ public class ValidationFailure {
 		/// <summary>
 		/// Creates a new ValidationFailure.
 		/// </summary>
+		[JsonConstructor]
 		public ValidationFailure(string propertyName, string errorMessage, object attemptedValue) {
 			PropertyName = propertyName;
 			ErrorMessage = errorMessage;

src/FluentValidation/Results/ValidationResult.cs

@@ -20,6 +20,7 @@ namespace FluentValidation.Results {
 	using System;
 	using System.Collections.Generic;
 	using System.Linq;
+	using System.Text.Json.Serialization;
 
 	/// <summary>
 	/// The result of running a validator
@@ -47,6 +48,15 @@ public class ValidationResult {
 			_errors = new List<ValidationFailure>();
 		}
 
+		/// <summary>
+		/// Helps System.Text.Json to deserialize jsons correctly. This constructor cannot be called for other purposes.
+		/// </summary>
+		[Obsolete]
+		[JsonConstructor]
+		public ValidationResult(List<ValidationFailure> errors , bool isValid) {
+			_errors = errors;
+		}
+
 		/// <summary>
 		/// Creates a new ValidationResult from a collection of failures
 		/// </summary>