Use JsonPolymorphic feature of System.Text.Json

.config/dotnet-tools.json

@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "dotnet-format": {
-      "version": "5.1.225507",
+      "version": "5.1.250801",
       "commands": [
         "dotnet-format"
       ]

src/xunit.v3.common.tests/Messages/BaseMessages/_MessageSinkMessageTests.cs

@@ -1,8 +1,11 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reflection;
 using System.Text;
+using System.Text.Json.Serialization;
 using Xunit;
+using Xunit.Internal;
 using Xunit.Sdk;
 using Xunit.v3;
 
@@ -15,7 +18,12 @@ public void BaseSerializationIncludesTypeName()
 
 		var result = Encoding.UTF8.GetString(msg.ToJson());
 
-		Assert.Equal(@"{""$type"":""_MessageSinkMessage""}", result);
+		var expected = """
+		{
+			"$type": "_MessageSinkMessage"
+		}
+		""".Replace("\n", "");
+		Assert.Equal(expected, result, ignoreAllWhiteSpace: true);
 	}
 
 	[Fact]
@@ -35,33 +43,56 @@ public void SerializationExcludesNullValues()
 
 		var result = Encoding.UTF8.GetString(msg.ToJson());
 
-		Assert.Equal(
-			@"{" +
-				@"""$type"":""_TestAssemblyStarting""," +
-				@"""AssemblyName"":""asm-name""," +
-				@"""AssemblyUniqueID"":""asm-id""," +
-				@"""StartTime"":""2020-09-26T13:55:27.212-07:00""," +
-				@"""TestEnvironment"":""test-env""," +
-				@"""TestFrameworkDisplayName"":""test-framework""" +
-			@"}",
-			result
-		);
+		var expected = """
+		{
+			"$type":                    "_TestAssemblyStarting",
+			"AssemblyName":             "asm-name",
+			"StartTime":                "2020-09-26T13:55:27.212-07:00",
+			"TestEnvironment":          "test-env",
+			"TestFrameworkDisplayName": "test-framework",
+			"AssemblyUniqueID":         "asm-id"
+		}
+		""".Replace("\n", "");
+		Assert.Equal(expected, result, ignoreAllWhiteSpace: true);
 	}
 
 	[Fact]
 	public void SerializesEnumsAsStrings()
 	{
-		var msg = new TestMessageWithEnum { Cause = FailureCause.Assertion };
+		var msg = new _TestFailed
+		{
+			AssemblyUniqueID = "asm-id",
+			Cause = FailureCause.Assertion,
+			ExceptionParentIndices = new[] { -1 },
+			ExceptionTypes = new[] { "exception-type" },
+			ExecutionTime = 123.45m,
+			Messages = new[] { "exception-message" },
+			Output = "",
+			StackTraces = new[] { "stack-trace" },
+			TestCaseUniqueID = "test-case-id",
+			TestCollectionUniqueID = "test-collection-id",
+			TestUniqueID = "test-id",
+		};
 
 		var result = Encoding.UTF8.GetString(msg.ToJson());
 
-		Assert.Equal(
-			@"{" +
-				@"""$type"":""TestMessageWithEnum""," +
-				@"""Cause"":""Assertion""" +
-			@"}",
-			result
-		);
+		var expected = """
+		{
+			"$type":                  "_TestFailed",
+			"Cause":                  "Assertion",
+			"ExceptionParentIndices": [-1],
+			"ExceptionTypes":         ["exception-type"],
+			"Messages":               ["exception-message"],
+			"StackTraces":            ["stack-trace"],
+			"ExecutionTime":          123.45,
+			"Output":                 "",
+			"TestUniqueID":           "test-id",
+			"TestCaseUniqueID":       "test-case-id",
+			"TestCollectionUniqueID": "test-collection-id",
+			"AssemblyUniqueID":       "asm-id"
+		}
+		""".Replace("\n", "");
+		Assert.Equal(expected, result, ignoreAllWhiteSpace: true);
 	}
 
 	class TestMessageWithEnum : _MessageSinkMessage
@@ -70,13 +101,24 @@ class TestMessageWithEnum : _MessageSinkMessage
 	}
 
 	[Fact]
-	public void CanDeserializeStringEnum()
+	public void DeserializesEnumsAsStrings()
 	{
-		var msg =
-			@"{" +
-				@"""$type"":""_TestFailed""," +
-				@"""Cause"":""Assertion""" +
-			@"}";
+		var msg = """
+		{
+			"$type":                  "_TestFailed",
+			"Cause":                  "Assertion",
+			"ExceptionParentIndices": [-1],
+			"ExceptionTypes":         ["exception-type"],
+			"Messages":               ["exception-message"],
+			"StackTraces":            ["stack-trace"],
+			"ExecutionTime":          123.45,
+			"Output":                 "",
+			"TestUniqueID":           "test-id",
+			"TestCaseUniqueID":       "test-case-id",
+			"TestCollectionUniqueID": "test-collection-id",
+			"AssemblyUniqueID":       "asm-id"
+		}
+		""";
 
 		var result = _MessageSinkMessage.ParseJson(Encoding.UTF8.GetBytes(msg));
 
@@ -106,23 +148,23 @@ public void CanRoundTripTraits()
 
 		var serialized = msg.ToJson();
 
-		Assert.Equal(
-			@"{" +
-				@"""$type"":""_TestCaseDiscovered""," +
-				@"""AssemblyUniqueID"":""asm-id""," +
-				@"""Serialization"":""serialized-value""," +
-				@"""TestCaseDisplayName"":""test-case-display-name""," +
-				@"""TestCaseUniqueID"":""test-case-id""," +
-				@"""TestCollectionUniqueID"":""test-collection-id""," +
-				@"""Traits"":" +
-				@"{" +
-					@"""foo"":[""bar"",""baz""]," +
-					@"""abc"":[""123""]," +
-					@"""empty"":[]" +
-				@"}" +
-			@"}",
-			Encoding.UTF8.GetString(serialized)
-		);
+		var expected = """
+		{
+			"$type":               "_TestCaseDiscovered",
+			"Serialization":       "serialized-value",
+			"TestCaseDisplayName": "test-case-display-name",
+			"Traits":
+			{
+				"foo":   ["bar", "baz"],
+				"abc":   ["123"],
+				"empty": []
+			},
+			"TestCaseUniqueID":       "test-case-id",
+			"TestCollectionUniqueID": "test-collection-id",
+			"AssemblyUniqueID":       "asm-id"
+		}
+		""".Replace("\n", "");
+		Assert.Equal(expected, Encoding.UTF8.GetString(serialized), ignoreAllWhiteSpace: true);
 
 		// Validate deserialization
 
@@ -160,4 +202,34 @@ public void RoundTrip()
 		var deserializedTAM = Assert.IsType<_TestAssemblyMessage>(deserialized);
 		Assert.Equal("asm-id", deserializedTAM.AssemblyUniqueID);
 	}
+
+	[Fact]
+	public void ValidatesAllDerivedTypesAreSupported()
+	{
+		var messageSinkMessageType = typeof(_MessageSinkMessage);
+		var missingTypes = new List<Type>();
+		var decoratedTypes =
+			messageSinkMessageType
+				.GetCustomAttributes(typeof(JsonDerivedTypeAttribute))
+				.Cast<JsonDerivedTypeAttribute>()
+				.Select(a => a.DerivedType)
+				.ToHashSet();
+
+		Type[] publicTypes;
+		try
+		{
+			publicTypes = messageSinkMessageType.Assembly.GetTypes();
+		}
+		catch (ReflectionTypeLoadException ex)
+		{
+			publicTypes = ex.Types.WhereNotNull().ToArray();
+		}
+
+		foreach (var type in publicTypes.Where(t => !t.IsAbstract && messageSinkMessageType.IsAssignableFrom(t)))
+			if (!decoratedTypes.Contains(type))
+				missingTypes.Add(type);
+
+		if (missingTypes.Count > 0)
+			throw new XunitException($"The following attributes are missing from {nameof(_MessageSinkMessage)}:{Environment.NewLine}{string.Join(Environment.NewLine, missingTypes.OrderBy(t => t.Name).Select(t => $"  [JsonDerivedType(typeof({t.Name}), nameof({t.Name}))]"))}");
+	}
 }

src/xunit.v3.common/Utility/UnsetPropertiesException.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Xunit.Internal;
+
+namespace Xunit.Sdk;
+
+/// <summary>
+/// An exception which indicates an object had several properties that were not properly initialized.
+/// </summary>
+public class UnsetPropertiesException : InvalidOperationException
+{
+	/// <summary>
+	/// Initializes a new instance of the <see cref="UnsetPropertiesException"/> class.
+	/// </summary>
+	/// <param name="propertyNames">The properties that were not set</param>
+	/// <param name="type">The type that the property belongs to</param>
+	public UnsetPropertiesException(
+		IEnumerable<string> propertyNames,
+		Type type)
+	{
+		PropertyNames = Guard.ArgumentNotNull(propertyNames).OrderBy(x => x).ToArray();
+		TypeName = Guard.ArgumentNotNull(type).SafeName();
+	}
+
+	/// <inheritdoc/>
+	public override string Message =>
+		$"Object of type '{TypeName}' had one or more properties that were not set: {string.Join(", ", PropertyNames)}";
+
+	/// <summary>
+	/// Gets the property names of the uninitialized properties.
+	/// </summary>
+	public string[] PropertyNames { get; }
+
+	/// <summary>
+	/// Gets the type name of the uninitialized property.
+	/// </summary>
+	public string TypeName { get; }
+}

src/xunit.v3.common/Utility/UnsetPropertyException.cs

@@ -12,8 +12,8 @@ public class UnsetPropertyException : InvalidOperationException
 	/// <summary>
 	/// Initializes a new instance of the <see cref="UnsetPropertyException"/> class.
 	/// </summary>
-	/// <param name="propertyName"></param>
-	/// <param name="type"></param>
+	/// <param name="propertyName">The property that was not set</param>
+	/// <param name="type">The type that the property belongs to</param>
 	public UnsetPropertyException(
 		string propertyName,
 		Type type)