Add xUnit serializers for our types

Directory.Packages.props

@@ -10,6 +10,7 @@
 		<PackageVersion Include="xunit.assert" Version="[2.9.3, 2.10)" />
 		<PackageVersion Include="xunit.extensibility.core" Version="[2.9.3, 2.10)" />
 		<PackageVersion Include="xunit.v3.assert" Version="[1.0.1, 2)" />
+		<PackageVersion Include="xunit.v3.extensibility.core" Version="[1.0.1, 2)" />
 		<PackageVersion Include="System.Linq.Async" Version="[5.0.0, 7)" />
 	</ItemGroup>
 	<ItemGroup Label="Build Dependencies">

Funcky.Xunit.v3.Test/Funcky.Xunit.v3.Test.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <TargetFramework>net9.0</TargetFramework>
         <LangVersion>preview</LangVersion>
@@ -24,4 +24,5 @@
     <Import Project="..\Analyzers.props" />
     <Import Project="..\GlobalUsings.props" />
     <Import Project="..\GlobalUsings.Test.props" />
+    <Import Project="..\Funcky.Xunit.v3\build\Funcky.Xunit.v3.targets" />
 </Project>

Funcky.Xunit.v3.Test/Serializers/EitherSerializerTest.cs

@@ -0,0 +1,38 @@
+using Funcky.Xunit.Serializers;
+
+namespace Funcky.Xunit.Test;
+
+public sealed class EitherSerializerTest
+{
+    private static readonly EitherSerializer Serializer = new();
+
+    [Theory]
+    [MemberData(nameof(EitherProvider))]
+    public void RoundtripsEitherValues(IEither either)
+    {
+        Assert.True(Serializer.IsSerializable(either.GetType(), either, out _));
+        var serialized = Serializer.Serialize(either);
+        var deserialized = Serializer.Deserialize(either.GetType(), serialized);
+        Assert.Equal(either, deserialized);
+    }
+
+    public static TheoryData<IEither> EitherProvider()
+        => new((IEnumerable<IEither>)[
+            Either<string>.Return(10),
+            Either<string>.Return(20),
+            Either<string, int>.Left("foo"),
+            Either<string, int>.Left("bar"),
+            Either<string, int>.Left("bar"),
+            Either<NonSerializable, int>.Right(42),
+            Either<int, NonSerializable>.Left(42),
+        ]);
+
+    [Fact]
+    public void EitherSideOfNonSerializableTypeIsNotSerializable()
+    {
+        Assert.False(Serializer.IsSerializable(typeof(Either<NonSerializable, int>), Either<NonSerializable, int>.Left(new NonSerializable()), out _));
+        Assert.False(Serializer.IsSerializable(typeof(Either<int, NonSerializable>), Either<int, NonSerializable>.Right(new NonSerializable()), out _));
+    }
+
+    public sealed class NonSerializable;
+}

Funcky.Xunit.v3.Test/Serializers/OptionSerializerTest.cs

@@ -0,0 +1,45 @@
+using Funcky.Xunit.Serializers;
+
+namespace Funcky.Xunit.Test;
+
+public sealed class OptionSerializerTest
+{
+    private static readonly OptionSerializer Serializer = new();
+
+    [Theory]
+    [MemberData(nameof(OptionProvider))]
+    public void RoundtripsOptionValues(Option<int> option)
+    {
+        var serialized = Serializer.Serialize(option);
+        var deserialized = Serializer.Deserialize(option.GetType(), serialized);
+        Assert.Equal(option, deserialized);
+    }
+
+    public static TheoryData<Option<int>> OptionProvider()
+        => [
+            Option.Some(10),
+            Option.Some(20),
+            Option<int>.None,
+        ];
+
+    [Fact]
+    public void OptionOfSerializableTypeIsSerializable()
+    {
+        Assert.True(Serializer.IsSerializable(typeof(Option<int>), Option.Some(10), out _));
+        Assert.True(Serializer.IsSerializable(typeof(Option<int>), Option<int>.None, out _));
+    }
+
+    [Fact]
+    public void OptionOfNonSerializableTypeIsNotSerializable()
+    {
+        Assert.False(Serializer.IsSerializable(typeof(Option<NonSerializable>), Option.Some(new NonSerializable()), out _));
+    }
+
+    [Fact]
+    public void NoneIsAlwaysSerializable()
+    {
+        Assert.True(Serializer.IsSerializable(typeof(Option<NonSerializable>), Option<NonSerializable>.None, out _));
+    }
+
+    public sealed class NonSerializable;
+}

Funcky.Xunit.v3.Test/Serializers/UnitSerializerTest.cs

@@ -0,0 +1,22 @@
+using Funcky.Xunit.Serializers;
+
+namespace Funcky.Xunit.Test;
+
+public sealed class UnitSerializerTest
+{
+    private static readonly UnitSerializer Serializer = new();
+
+    [Fact]
+    public void RoundtripsUnit()
+    {
+        var serialized = Serializer.Serialize(Unit.Value);
+        var deserialized = Serializer.Deserialize(typeof(Unit), serialized);
+        Assert.Equal(Unit.Value, deserialized);
+    }
+
+    [Fact]
+    public void UnitIsSerializable()
+    {
+        Assert.True(Serializer.IsSerializable(typeof(Unit), Unit.Value, out _));
+    }
+}

Funcky.Xunit.v3/Funcky.Xunit.v3.csproj

@@ -19,13 +19,20 @@
     <PropertyGroup Condition="'$(TargetFramework)' == 'net6.0'">
         <DefineConstants>$(DefineConstants);STACK_TRACE_HIDDEN_SUPPORTED</DefineConstants>
     </PropertyGroup>
+    <ItemGroup>
+        <InternalsVisibleTo Include="Funcky.Xunit.v3.Test" />
+    </ItemGroup>
     <ItemGroup>
         <Compile Include="..\Funcky.Xunit\**\*.cs" />
     </ItemGroup>
+    <ItemGroup>
+        <None Include="build\$(PackageId).targets" Pack="true" PackagePath="build\" />
+    </ItemGroup>
     <ItemGroup>
         <PackageReference Include="PolySharp" PrivateAssets="all" />
         <PackageReference Include="Polyadic.Build.SemanticVersioning" PrivateAssets="all" />
         <PackageReference Include="xunit.v3.assert" />
+        <PackageReference Include="xunit.v3.extensibility.core" />
         <PackageReference Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" PrivateAssets="all" Condition="'$(TargetFramework)' == 'net6.0'" />
     </ItemGroup>
     <ItemGroup>

Funcky.Xunit.v3/PublicAPI.Unshipped.txt

@@ -1,4 +1,10 @@
 #nullable enable
+Funcky.Xunit.RegisterEitherSerializerAttribute
+Funcky.Xunit.RegisterEitherSerializerAttribute.RegisterEitherSerializerAttribute() -> void
+Funcky.Xunit.RegisterOptionSerializerAttribute
+Funcky.Xunit.RegisterOptionSerializerAttribute.RegisterOptionSerializerAttribute() -> void
+Funcky.Xunit.RegisterUnitSerializerAttribute
+Funcky.Xunit.RegisterUnitSerializerAttribute.RegisterUnitSerializerAttribute() -> void
 static Funcky.FunctionalAssert.Some<TItem>(TItem expectedValue, Funcky.Monads.Option<TItem> option) -> void
 static Funcky.FunctionalAssert.Some<TItem>(Funcky.Monads.Option<TItem> option) -> TItem
 static Funcky.FunctionalAssert.Right<TLeft, TRight>(TRight expectedRight, Funcky.Monads.Either<TLeft, TRight> either) -> void

Funcky.Xunit.v3/RegisterEitherSerializerAttribute.cs

@@ -0,0 +1,14 @@
+using System.ComponentModel;
+using Funcky.Xunit.Serializers;
+using Xunit.Sdk;
+
+namespace Funcky.Xunit;
+
+[AttributeUsage(AttributeTargets.Assembly)]
+[EditorBrowsable(EditorBrowsableState.Advanced)]
+public sealed class RegisterEitherSerializerAttribute : Attribute, IRegisterXunitSerializerAttribute
+{
+    Type IRegisterXunitSerializerAttribute.SerializerType => typeof(EitherSerializer);
+
+    Type[] IRegisterXunitSerializerAttribute.SupportedTypesForSerialization => [typeof(IEither)];
+}

Funcky.Xunit.v3/RegisterOptionSerializerAttribute.cs

@@ -0,0 +1,14 @@
+using System.ComponentModel;
+using Funcky.Xunit.Serializers;
+using Xunit.Sdk;
+
+namespace Funcky.Xunit;
+
+[AttributeUsage(AttributeTargets.Assembly)]
+[EditorBrowsable(EditorBrowsableState.Advanced)]
+public sealed class RegisterOptionSerializerAttribute : Attribute, IRegisterXunitSerializerAttribute
+{
+    Type IRegisterXunitSerializerAttribute.SerializerType => typeof(OptionSerializer);
+
+    Type[] IRegisterXunitSerializerAttribute.SupportedTypesForSerialization => [typeof(IOption)];
+}

Funcky.Xunit.v3/RegisterUnitSerializerAttribute.cs

@@ -0,0 +1,14 @@
+using System.ComponentModel;
+using Funcky.Xunit.Serializers;
+using Xunit.Sdk;
+
+namespace Funcky.Xunit;
+
+[AttributeUsage(AttributeTargets.Assembly)]
+[EditorBrowsable(EditorBrowsableState.Advanced)]
+public sealed class RegisterUnitSerializerAttribute : Attribute, IRegisterXunitSerializerAttribute
+{
+    Type IRegisterXunitSerializerAttribute.SerializerType => typeof(UnitSerializer);
+
+    Type[] IRegisterXunitSerializerAttribute.SupportedTypesForSerialization => [typeof(Unit)];
+}

Funcky.Xunit.v3/Serializers/EitherSerializer.cs

@@ -0,0 +1,86 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+using Xunit.Sdk;
+using static Funcky.Discard;
+
+namespace Funcky.Xunit.Serializers;
+
+internal sealed class EitherSerializer : IXunitSerializer
+{
+    private static readonly MethodInfo GenericDeserialize
+        = typeof(EitherSerializer).GetMethod(nameof(Deserialize), BindingFlags.Static | BindingFlags.NonPublic)
+          ?? throw new MissingMethodException("Generic deserialize method not found");
+
+    private static readonly MethodInfo GenericIsSerializable
+        = typeof(EitherSerializer).GetMethod(nameof(IsSerializable), BindingFlags.Static | BindingFlags.NonPublic)
+          ?? throw new MissingMethodException("Generic IsSerializable method not found");
+
+    private static readonly MethodInfo GenericSerialize
+        = typeof(EitherSerializer).GetMethod(nameof(Serialize), BindingFlags.Static | BindingFlags.NonPublic)
+            ?? throw new MissingMethodException("Generic serialize method not found");
+
+    public object Deserialize(Type type, string serializedValue)
+    {
+        var (leftType, rightType) = GetLeftAndRightTypeOrThrow(type);
+        return GenericDeserialize.MakeGenericMethod(leftType, rightType).Invoke(null, [serializedValue])!;
+    }
+
+    public bool IsSerializable(Type type, object? value, [NotNullWhen(false)] out string? failureReason)
+    {
+        failureReason = string.Empty;
+        return GetLeftAndRightType(type) is [var (leftType, rightType)]
+            && (bool)GenericIsSerializable.MakeGenericMethod(leftType, rightType).Invoke(null, [leftType, rightType, value])!;
+    }
+
+    public string Serialize(object value)
+    {
+        var (leftType, rightType) = GetLeftAndRightTypeOrThrow(value.GetType());
+        return (string)GenericSerialize.MakeGenericMethod(leftType, rightType).Invoke(null, [value])!;
+    }
+
+    private static (Type Left, Type Right) GetLeftAndRightTypeOrThrow(Type eitherType)
+        => GetLeftAndRightType(eitherType).GetOrElse(() => throw new InvalidOperationException($"{eitherType} is not an Either<L, R>"));
+
+    private static Option<(Type Left, Type Right)> GetLeftAndRightType(Type eitherType)
+        => eitherType.IsGenericType && eitherType.GetGenericTypeDefinition() == typeof(Either<,>)
+            ? (eitherType.GenericTypeArguments[0], eitherType.GenericTypeArguments[1])
+            : Option<(Type, Type)>.None;
+
+    private static object Deserialize<TLeft, TRight>(string serializedValue)
+        where TLeft : notnull
+        where TRight : notnull
+        => __ switch
+        {
+            _ when serializedValue.StripPrefix(Tag.Left) is [var rest]
+                => Either<TLeft, TRight>.Left(SerializationHelper.Instance.Deserialize<TLeft>(rest)!),
+            _ when serializedValue.StripPrefix(Tag.Right) is [var rest]
+                => Either<TLeft, TRight>.Right(SerializationHelper.Instance.Deserialize<TRight>(rest)!),
+            _ => throw new FormatException($"'{serializedValue}' is not a valid either value"),
+        };
+
+    private static bool IsSerializable<TLeft, TRight>(Type leftType, Type rightType, object? value)
+        where TLeft : notnull
+        where TRight : notnull
+    {
+        var either = (Either<TLeft, TRight>)(value ?? throw new InvalidOperationException("Either cannot be null"));
+        return either.Match(
+            left: left => SerializationHelper.Instance.IsSerializable(left, leftType),
+            right: right => SerializationHelper.Instance.IsSerializable(right, rightType));
+    }
+
+    private static string Serialize<TLeft, TRight>(object obj)
+        where TLeft : notnull
+        where TRight : notnull
+    {
+        var either = (Either<TLeft, TRight>)obj;
+        return either.Match(
+            left: left => $"{Tag.Left}{SerializationHelper.Instance.Serialize(left)}",
+            right: right => $"{Tag.Right}{SerializationHelper.Instance.Serialize(right)}");
+    }
+
+    private static class Tag
+    {
+        public const string Left = "L:";
+        public const string Right = "R:";
+    }
+}

Funcky.Xunit.v3/Serializers/OptionSerializer.cs

@@ -0,0 +1,79 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+using Xunit.Sdk;
+using static Funcky.Discard;
+
+namespace Funcky.Xunit.Serializers;
+
+internal sealed class OptionSerializer : IXunitSerializer
+{
+    private static readonly MethodInfo GenericDeserialize
+        = typeof(OptionSerializer).GetMethod(nameof(Deserialize), BindingFlags.Static | BindingFlags.NonPublic)
+          ?? throw new MissingMethodException("Generic deserialize method not found");
+
+    private static readonly MethodInfo GenericIsSerializable
+        = typeof(OptionSerializer).GetMethod(nameof(IsSerializable), BindingFlags.Static | BindingFlags.NonPublic)
+          ?? throw new MissingMethodException("Generic IsSerializable method not found");
+
+    private static readonly MethodInfo GenericSerialize
+        = typeof(OptionSerializer).GetMethod(nameof(Serialize), BindingFlags.Static | BindingFlags.NonPublic)
+            ?? throw new MissingMethodException("Generic serialize method not found");
+
+    public object Deserialize(Type type, string serializedValue)
+    {
+        var itemType = GetItemTypeOrThrow(type);
+        return GenericDeserialize.MakeGenericMethod(itemType).Invoke(null, [serializedValue])!;
+    }
+
+    public bool IsSerializable(Type type, object? value, [NotNullWhen(false)] out string? failureReason)
+    {
+        failureReason = string.Empty;
+        return GetItemType(type) is [var itemType]
+            && (bool)GenericIsSerializable.MakeGenericMethod(itemType).Invoke(null, [itemType, value])!;
+    }
+
+    public string Serialize(object value)
+    {
+        var itemType = GetItemTypeOrThrow(value.GetType());
+        return (string)GenericSerialize.MakeGenericMethod(itemType).Invoke(null, [value])!;
+    }
+
+    private static Type GetItemTypeOrThrow(Type eitherType)
+        => GetItemType(eitherType).GetOrElse(() => throw new InvalidOperationException($"{eitherType} is not an Option<T>"));
+
+    private static Option<Type> GetItemType(Type optionType)
+        => optionType.IsGenericType && optionType.GetGenericTypeDefinition() == typeof(Option<>)
+            ? optionType.GenericTypeArguments.First()
+            : Option<Type>.None;
+
+    private static object Deserialize<TItem>(string serializedValue)
+        where TItem : notnull
+        => __ switch
+        {
+            _ when serializedValue == Tag.None => Option<TItem>.None,
+            _ when serializedValue.StripPrefix(Tag.Some) is [var rest] => Option.Some(SerializationHelper.Instance.Deserialize<TItem>(rest)!),
+            _ => throw new FormatException($"'{serializedValue}' is not a valid option value"),
+        };
+
+    private static bool IsSerializable<TItem>(Type itemType, object? value)
+        where TItem : notnull
+    {
+        var option = (Option<TItem>)(value ?? throw new InvalidOperationException("TODO"));
+        return option.Match(none: true, some: item => SerializationHelper.Instance.IsSerializable(item, itemType));
+    }
+
+    private static string Serialize<TItem>(object obj)
+        where TItem : notnull
+    {
+        var option = (Option<TItem>)obj;
+        return option.Match(
+            none: () => Tag.None,
+            some: item => $"{Tag.Some}{SerializationHelper.Instance.Serialize(item)}");
+    }
+
+    private static class Tag
+    {
+        public const string None = "N";
+        public const string Some = "S:";
+    }
+}

Funcky.Xunit.v3/Serializers/StringExtensions.cs

@@ -0,0 +1,9 @@
+namespace Funcky.Xunit.Serializers;
+
+internal static class StringExtensions
+{
+    public static Option<string> StripPrefix(this string s, string prefix)
+        => s.StartsWith(prefix)
+            ? s[prefix.Length..]
+            : Option<string>.None;
+}

Funcky.Xunit.v3/Serializers/UnitSerializer.cs

@@ -0,0 +1,17 @@
+using System.Diagnostics.CodeAnalysis;
+using Xunit.Sdk;
+
+namespace Funcky.Xunit.Serializers;
+
+internal sealed class UnitSerializer : IXunitSerializer
+{
+    public object Deserialize(Type type, string serializedValue) => Unit.Value;
+
+    public bool IsSerializable(Type type, object? value, [NotNullWhen(false)] out string? failureReason)
+    {
+        failureReason = string.Empty;
+        return type == typeof(Unit);
+    }
+
+    public string Serialize(object value) => string.Empty;
+}