removed some new lang features to support net6.0 and net7.0

.gitea/workflows/publish-nuget.yaml

@@ -22,13 +22,17 @@ jobs:
       run: dotnet restore Railway/Railway.csproj
 
     - name: Setup nuget source
-      run: dotnet nuget add source --name gitea_registry https://gitea.jstdev.ru/api/packages/just/nuget/index.json
+      run: dotnet nuget add source --name gitea_registry ${{ vars.OUTPUT_NUGET_REGISTRY }} 
 
     - name: Create the package
       env:
         RELEASE_VERSION: ${{ gitea.ref_name }}
-      run: dotnet pack --no-restore --configuration Release --output nupkgs Railway/Railway.csproj `echo $RELEASE_VERSION | sed -E 's|^(v([0-9]+(\.[0-9]+){2}))(-([a-z0-9]+)){1}|/p:ReleaseVersion=\2 /p:VersionSuffix=\5|; s|^(v([0-9]+(\.[0-9]+){2}))$|/p:ReleaseVersion=\2|'`
+      run: >
+        dotnet pack --no-restore --configuration Release --output nupkgs Railway/Railway.csproj
+        `echo $RELEASE_VERSION | sed -E 's|^(v([0-9]+(\.[0-9]+){2}))(-([a-z0-9]+)){1}|/p:ReleaseVersion=\2 /p:VersionSuffix=\5|; s|^(v([0-9]+(\.[0-9]+){2}))$|/p:ReleaseVersion=\2|'`
 
     - name: Publish the package to Gitea
-      run: dotnet nuget push --source gitea_registry --api-key ${{ secrets.NUGET_PACKAGE_TOKEN }} nupkgs/*.nupkg
+      run: dotnet nuget push --source gitea_registry --api-key ${{ secrets.LOCAL_NUGET_PACKAGE_TOKEN }} nupkgs/*.nupkg
 
+    - name: Publish the package to NuGet.org
+      run: dotnet nuget push --source https://api.nuget.org/v3/index.json --api-key ${{ secrets.NUGET_PACKAGE_TOKEN }} nupkgs/*.nupkg

README.md

@@ -4,6 +4,106 @@ This library uses features of C# to achieve railway-oriented programming.
 
 The desire is to make somewhat user-friendly experience while using result-object pattern.
 
-## Contents
+## Features
 
-_Coming soon..._
+- Immutable ```Error``` class
+- ```Result``` object
+- A bunch of extensions to use result-object pattern with
+- ```Try``` extensions to wrap function calls with result-object
+- ```Ensure``` extensions to utilize result-object in validation scenarios
+
+## Getting Started
+
+### Install from NuGet.org
+
+```sh
+# install the package using NuGet
+dotnet add package Just.Railway
+```
+
+## Examples
+
+### Error
+
+```csharp
+using Just.Railway;
+Error expectedError = Error.New(type: "Some Error", message: "Some error detail");
+Error exceptionalError = Error.New(new Exception("Some Exception"));
+Error manyErrors = Error.Many(expectedError, exceptionalError);
+// the same result while using .Append(..) or +
+manyErrors = expectedError.Append(exceptionalError);
+manyErrors = expectedError + exceptionalError;
+```
+
+> **Note**
+> You can easily serialize/deserialize Error to and from JSON
+
+### Result
+
+#### As return value:
+
+```csharp
+Result Foo()
+{
+    // ...
+    if (SomeCondition())
+        return Result.Failure(Error.New("Some Error"));
+        // or just: return Error.New("Some Error");
+    // ...
+    return Result.Success();
+}
+
+Result<T> Bar()
+{
+    T value;
+    // ...
+    if (SomeCondition())
+        return Error.New("Some Error");
+    // ...
+    return value;
+}
+```
+
+#### Consume Result object
+
+```csharp
+Result<int> result = GetResult();
+
+var value = result
+    .Append("new")
+    .Map((i, s) => $"{s} result {i}")
+    .Match(
+        onSuccess: x => x,
+        onFailure: err => err.ToString()
+    );
+// value: "new result 1"
+
+Result<int> GetResult() => Result.Success(1);
+```
+
+### Try
+
+```csharp
+Result result = Try.Run(SomeAction);
+// you can pass up to 5 arguments like this
+result = Try.Run(SomeActionWithArguments, 1, 2.0, "3");
+
+// you also can call functions
+Result<int> resultWithValue = Try.Run(SomeFunction);
+
+void SomeAction() {}
+void SomeActionWithArguments(int a1, double a2, string? a3) {}
+int SomeFunction() => 1;
+```
+
+### Ensure
+
+```csharp
+var value = GetValue();
+Result<int> result = Ensure.That(value)
+    .NotNull()
+    .Satisfies(i => i < 100)
+    .Result();
+
+int? GetValue() => 1;
+```

Railway.SourceGenerator/EnsureExtensionsExecutor.cs

@@ -7,7 +7,7 @@ using Microsoft.CodeAnalysis;
 
 namespace Just.Railway.SourceGen;
 
-public sealed class EnsureExtensionExecutor : IGeneratorExecutor
+public sealed class EnsureExtensionsExecutor : IGeneratorExecutor
 {
     public void Execute(SourceProductionContext context, Compilation source)
     {
@@ -80,7 +80,7 @@ public sealed class EnsureExtensionExecutor : IGeneratorExecutor
 
         typeOverloads.ForEach(def => sb.AppendLine($$"""
         [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(EnsureExtensionExecutor)}}", "1.0.0.0")]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
         public static Ensure<{{def.CollectionType}}> NotEmpty{{def.TemplateDef}}(this in Ensure<{{def.CollectionType}}> ensure, {{errorParameterDecl}})
         {
             return ensure.State switch
@@ -101,7 +101,7 @@ public sealed class EnsureExtensionExecutor : IGeneratorExecutor
 
         sb.AppendLine($$"""
         [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(EnsureExtensionExecutor)}}", "1.0.0.0")]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
         public static Ensure<T> NotNull<T>(this in Ensure<T?> ensure, {{errorParameterDecl}})
             where T : struct
         {
@@ -117,7 +117,7 @@ public sealed class EnsureExtensionExecutor : IGeneratorExecutor
         """);
         sb.AppendLine($$"""
         [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(EnsureExtensionExecutor)}}", "1.0.0.0")]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
         public static Ensure<T> NotNull<T>(this in Ensure<T?> ensure, {{errorParameterDecl}})
             where T : notnull
         {
@@ -138,7 +138,7 @@ public sealed class EnsureExtensionExecutor : IGeneratorExecutor
         string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} does not satisfy the requirement.\")";
         sb.AppendLine($$"""
         [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(EnsureExtensionExecutor)}}", "1.0.0.0")]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
         public static Ensure<T> Satisfies<T>(this in Ensure<T> ensure, Func<T, bool> requirement, {{errorParameterDecl}})
         {
             return ensure.State switch
@@ -160,7 +160,7 @@ public sealed class EnsureExtensionExecutor : IGeneratorExecutor
     {
         sb.AppendLine($$"""
         [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(EnsureExtensionExecutor)}}", "1.0.0.0")]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
         public static async {{taskType}}<Ensure<T>> Satisfies<T>(this {{taskType}}<Ensure<T>> ensureTask, Func<T, bool> requirement, {{errorParameterDecl}})
         {
             var ensure = await ensureTask.ConfigureAwait(false);
@@ -176,7 +176,7 @@ public sealed class EnsureExtensionExecutor : IGeneratorExecutor
         """);
         sb.AppendLine($$"""
         [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(EnsureExtensionExecutor)}}", "1.0.0.0")]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
         public static async {{taskType}}<Ensure<T>> Satisfies<T>(this Ensure<T> ensure, Func<T, {{taskType}}<bool>> requirement, {{errorParameterDecl}})
         {
             return ensure.State switch
@@ -191,7 +191,7 @@ public sealed class EnsureExtensionExecutor : IGeneratorExecutor
         """);
         sb.AppendLine($$"""
         [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(EnsureExtensionExecutor)}}", "1.0.0.0")]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
         public static async {{taskType}}<Ensure<T>> Satisfies<T>(this {{taskType}}<Ensure<T>> ensureTask, Func<T, {{taskType}}<bool>> requirement, {{errorParameterDecl}})
         {
             var ensure = await ensureTask.ConfigureAwait(false);

Railway.SourceGenerator/ExtensionsMethodGenerator.cs

@@ -19,7 +19,7 @@ public class ExtensionsMethodGenerator : IIncrementalGenerator
         new ResultTapExecutor(),
         new ResultAppendExecutor(),
         new TryExtensionsExecutor(),
-        new EnsureExtensionExecutor(),
+        new EnsureExtensionsExecutor(),
     };
 
     public void Initialize(IncrementalGeneratorInitializationContext context)

Railway.SourceGenerator/ResultAppendExecutor.cs

@@ -200,6 +200,48 @@ internal sealed class ResultAppendExecutor : ResultExtensionsExecutor
         string resultExpandedTypeDef = GenerateResultTypeDef(expandedTemplateArgNames);
         string methodExpandedTemplateDecl = GenerateTemplateDecl(expandedTemplateArgNames);
 
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, TNext next)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => Result.Success({{JoinArguments(resultValueExpansion, "next")}}),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Result<TNext> next)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            if ((result.State & next.State) == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
+            }
+
+            Error? error = null;
+            if (result.IsFailure)
+            {
+                error += result.Error;
+            }
+            if (next.IsFailure)
+            {
+                error += next.Error;
+            }
+
+            return error is null
+                ? Result.Success({{JoinArguments(resultValueExpansion, "next.Value")}})
+                : error;
+        }
+        """);
+
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]

Railway/Ensure.cs

@@ -60,6 +60,7 @@ public readonly struct Ensure<T>
         Value = value;
         ValueExpression = valueExpression;
         State = ResultState.Success;
+        Error = default;
     }
 
     internal Ensure(Error error, string valueExpression)
@@ -72,7 +73,12 @@ public readonly struct Ensure<T>
 }
 
 [Serializable]
-public class EnsureNotInitializedException(string variableName = "this") : InvalidOperationException("Ensure was not properly initialized.")
+public class EnsureNotInitializedException : InvalidOperationException
 {
-    public string VariableName { get; } = variableName;
+    public EnsureNotInitializedException(string variableName = "this")
+        : base("Ensure was not properly initialized.")
+    {
+        VariableName = variableName;
+    }
+    public string VariableName { get; }
 }

Railway/Error.cs

@@ -1,17 +1,12 @@
 using System.Collections;
-using System.Runtime.Serialization;
+using System.Collections.Immutable;
 using System.Text;
 
 namespace Just.Railway;
 
-[JsonPolymorphic(TypeDiscriminatorPropertyName = "$$err")]
-[JsonDerivedType(typeof(ExpectedError), typeDiscriminator: 0)]
-[JsonDerivedType(typeof(ExceptionalError), typeDiscriminator: 1)]
-[JsonDerivedType(typeof(ManyErrors))]
+[JsonConverter(typeof(ErrorJsonConverter))]
 public abstract class Error : IEquatable<Error>, IComparable<Error>
 {
-    private IDictionary<string, object>? _extensionData;
-
     protected internal Error(){}
 
     /// <summary>
@@ -34,16 +29,22 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
     /// </summary>
     /// <param name="message">Error detail</param>
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static Error New(string message) =>
-        new ExpectedError("error", message);
+    public static Error New(string message, IEnumerable<KeyValuePair<string, string>>? extensionData = null) =>
+        new ExpectedError("error", message)
+        {
+            ExtensionData = extensionData?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty
+        };
     /// <summary>
     /// Create an <see cref="ExpectedError"/>
     /// </summary>
     /// <param name="type">Error code</param>
     /// <param name="message">Error detail</param>
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static Error New(string type, string message) =>
-        new ExpectedError(type, message);
+    public static Error New(string type, string message, IEnumerable<KeyValuePair<string, string>>? extensionData = null) =>
+        new ExpectedError(type, message)
+        {
+            ExtensionData = extensionData?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty
+        };
     /// <summary>
     /// Create a <see cref="ManyErrors"/>
     /// </summary>
@@ -51,7 +52,7 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static Error Many(Error error1, Error error2) => (error1, error2) switch
     {
-        (null, null) => new ManyErrors(Enumerable.Empty<Error>()),
+        (null, null) => new ManyErrors(new List<Error>()),
         (Error err, null) => err,
         (Error err, { IsEmpty: true }) => err,
         (null, Error err) => err,
@@ -77,33 +78,14 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
 
     [Pure] public abstract string Type { get; }
     [Pure] public abstract string Message { get; }
-    [Pure, JsonExtensionData] public IDictionary<string, object> ExtensionData
-    {
-        get => _extensionData ??= new Dictionary<string, object>();
-        init => _extensionData = value ?? new Dictionary<string, object>();
-    }
-    [Pure] public object? this[string name]
-    {
-        get => _extensionData?.TryGetValue(name, out var val) == true ? val : null;
 
-        set
-        {
-            if (value is null)
-            {
-                _extensionData?.Remove(name);
-            }
-            else
-            {
-                _extensionData ??= new Dictionary<string, object>();
-                _extensionData[name] = value;
-            }
-        }
-    }
+    [Pure] public ImmutableDictionary<string, string> ExtensionData { get; internal init; } = ImmutableDictionary<string, string>.Empty;
+    [Pure] public string? this[string key] => ExtensionData.TryGetValue(key, out var value) == true ? value : null;
 
-    [Pure, JsonIgnore] public abstract int Count { get; }
-    [Pure, JsonIgnore] public abstract bool IsEmpty { get; }
-    [Pure, JsonIgnore] public abstract bool IsExpected { get; }
-    [Pure, JsonIgnore] public abstract bool IsExeptional { get; }
+    [Pure] public abstract int Count { get; }
+    [Pure] public abstract bool IsEmpty { get; }
+    [Pure] public abstract bool IsExpected { get; }
+    [Pure] public abstract bool IsExeptional { get; }
 
     [Pure] public Error Append(Error? next)
     {
@@ -163,9 +145,9 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
     }
 }
 
+[JsonConverter(typeof(ExpectedErrorJsonConverter))]
 public sealed class ExpectedError : Error
 {
-    [JsonConstructor]
     public ExpectedError(string type, string message)
     {
         Type = type;
@@ -179,10 +161,10 @@ public sealed class ExpectedError : Error
     [Pure] public override string Type { get; }
     [Pure] public override string Message { get; }
 
-    [Pure, JsonIgnore] public override int Count => 1;
-    [Pure, JsonIgnore] public override bool IsEmpty => false;
-    [Pure, JsonIgnore] public override bool IsExpected => true;
-    [Pure, JsonIgnore] public override bool IsExeptional => false;
+    [Pure] public override int Count => 1;
+    [Pure] public override bool IsEmpty => false;
+    [Pure] public override bool IsExpected => true;
+    [Pure] public override bool IsExeptional => false;
 
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public override IEnumerable<Error> ToEnumerable()
@@ -191,24 +173,24 @@ public sealed class ExpectedError : Error
     }
 }
 
+[JsonConverter(typeof(ExceptionalErrorJsonConverter))]
 public sealed class ExceptionalError : Error
 {
     internal readonly Exception? Exception;
 
     internal ExceptionalError(Exception exception)
-        : this(exception.GetType().Name, exception.Message)
+        : this(exception.GetType().FullName ?? exception.GetType().Name, exception.Message)
     {
         Exception = exception;
-        FillExtensionData(exception);
+        ExtensionData = ExtractExtensionData(exception);
     }
     internal ExceptionalError(string message, Exception exception)
-        : this(exception.GetType().Name, message)
+        : this(exception.GetType().FullName ?? exception.GetType().Name, message)
     {
         Exception = exception;
-        FillExtensionData(exception);
+        ExtensionData = ExtractExtensionData(exception);
     }
 
-    [JsonConstructor]
     public ExceptionalError(string type, string message)
     {
         Type = type;
@@ -218,10 +200,10 @@ public sealed class ExceptionalError : Error
     [Pure] public override string Type { get; }
     [Pure] public override string Message { get; }
 
-    [Pure, JsonIgnore] public override int Count => 1;
-    [Pure, JsonIgnore] public override bool IsEmpty => false;
-    [Pure, JsonIgnore] public override bool IsExpected => false;
-    [Pure, JsonIgnore] public override bool IsExeptional => true;
+    [Pure] public override int Count => 1;
+    [Pure] public override bool IsEmpty => false;
+    [Pure] public override bool IsExpected => false;
+    [Pure] public override bool IsExeptional => true;
 
     [Pure] public override Exception ToException() => Exception ?? base.ToException();
 
@@ -231,24 +213,38 @@ public sealed class ExceptionalError : Error
         yield return this;
     }
 
-    private void FillExtensionData(Exception exception)
+    private static ImmutableDictionary<string, string> ExtractExtensionData(Exception exception)
     {
+        if (!(exception.Data?.Count > 0))
+        return ImmutableDictionary<string, string>.Empty;
+
+        List<KeyValuePair<string, string>>? values = null;
+
         foreach (var key in exception.Data.Keys)
         {
+            if (key is null) continue;
+
             var value = exception.Data[key];
-            if (key is null || value is null)
-                continue;
-            this.ExtensionData[key.ToString() ?? string.Empty] = value;
+            if (value is null) continue;
+
+            var keyString = key.ToString();
+            var valueString = value.ToString();
+            if (string.IsNullOrEmpty(keyString) || string.IsNullOrEmpty(valueString)) continue;
+
+            values ??= new List<KeyValuePair<string, string>>(4);
+            values.Add(new(keyString, valueString));
         }
+        return values?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty;
     }
 }
 
-[DataContract]
-public sealed class ManyErrors : Error, IEnumerable<Error>
+[JsonConverter(typeof(ManyErrorsJsonConverter))]
+public sealed class ManyErrors : Error, IEnumerable<Error>, IReadOnlyList<Error>
 {
     private readonly List<Error> _errors;
-    [Pure, DataMember] public IEnumerable<Error> Errors { get => _errors; }
+    [Pure] public IEnumerable<Error> Errors { get => _errors; }
 
+    internal ManyErrors(List<Error> errors) => _errors = errors;
     internal ManyErrors(Error head, Error tail)
     {
         _errors = new List<Error>(head.Count + tail.Count);
@@ -291,9 +287,11 @@ public sealed class ManyErrors : Error, IEnumerable<Error>
     }
 
     [Pure] public override int Count => _errors.Count;
-    [Pure, JsonIgnore] public override bool IsEmpty => _errors.Count == 0;
-    [Pure, JsonIgnore] public override bool IsExpected => _errors.All(static x => x.IsExpected);
-    [Pure, JsonIgnore] public override bool IsExeptional => _errors.Any(static x => x.IsExeptional);
+    [Pure] public override bool IsEmpty => _errors.Count == 0;
+    [Pure] public override bool IsExpected => _errors.All(static x => x.IsExpected);
+    [Pure] public override bool IsExeptional => _errors.Any(static x => x.IsExeptional);
+
+    [Pure] public Error this[int index] => _errors[index];
 
     [Pure] public override Exception ToException() => new AggregateException(_errors.Select(static x => x.ToException()));
     [Pure] public override IEnumerable<Error> ToEnumerable() => _errors;
@@ -379,7 +377,11 @@ public sealed class ManyErrors : Error, IEnumerable<Error>
 }
 
 [Serializable]
-public sealed class ErrorException(string type, string message) : Exception(message)
+public sealed class ErrorException : Exception
 {
-    public string Type { get; } = type ?? nameof(ErrorException);
+    public ErrorException(string type, string message) : base(message)
+    {
+        Type = type ?? nameof(ErrorException);
+    }
+    public string Type { get; }
 }

Railway/ErrorJsonConverter.cs

@@ -0,0 +1,182 @@
+using System.Collections.Immutable;
+
+namespace Just.Railway;
+
+public sealed class ErrorJsonConverter : JsonConverter<Error>
+{
+    public override Error? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartObject => ToExpectedError(ReadOne(ref reader)),
+            JsonTokenType.StartArray => ReadMany(ref reader),
+            JsonTokenType.None => null,
+            JsonTokenType.Null => null,
+            _ => throw new JsonException("Unexpected JSON token.")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, Error value, JsonSerializerOptions options)
+    {
+        if (value is ManyErrors manyErrors)
+        {
+            writer.WriteStartArray();
+            foreach (var err in manyErrors)
+            {
+                WriteOne(writer, err);
+            }
+            writer.WriteEndArray();
+        }
+        else
+        {
+            WriteOne(writer, value);
+        }
+    }
+
+    internal static ManyErrors ReadMany(ref Utf8JsonReader reader)
+    {
+        List<Error> errors = new(4);
+        while (reader.Read())
+        {
+            if (reader.TokenType == JsonTokenType.StartObject)
+            {
+                errors.Add(ToExpectedError(ReadOne(ref reader)));
+            }
+        }
+        return new ManyErrors(errors);
+    }
+    internal static ExpectedError ToExpectedError(in (string Type, string Message, ImmutableDictionary<string, string> ExtensionData) errorInfo)
+        => new(errorInfo.Type, errorInfo.Message) { ExtensionData = errorInfo.ExtensionData };
+    internal static (string Type, string Message, ImmutableDictionary<string, string> ExtensionData) ReadOne(ref Utf8JsonReader reader)
+    {
+        List<KeyValuePair<string, string>>? extensionData = null;
+        string type = "error";
+        string message = "";
+        while (reader.Read())
+        {
+            switch (reader.TokenType)
+            {
+                case JsonTokenType.PropertyName:
+                {
+                    var propname = reader.GetString();
+                    reader.Read();
+
+                    if (reader.TokenType == JsonTokenType.Null)
+                        break;
+
+                    while (reader.TokenType == JsonTokenType.Comment) reader.Read();
+
+                    if (!(reader.TokenType == JsonTokenType.String))
+                        throw new JsonException("Unable to deserialize Error type.");
+                    
+                    var propvalue = reader.GetString();
+                    if (string.IsNullOrEmpty(propvalue))
+                        break;
+
+                    if (propname == "type" || string.Equals(propname, "type", StringComparison.InvariantCultureIgnoreCase))
+                    {
+                        type = propvalue;
+                    }
+                    else if (propname == "msg" || string.Equals(propname, "msg", StringComparison.InvariantCultureIgnoreCase))
+                    {
+                        message = propvalue;
+                    }
+                    else if (!string.IsNullOrEmpty(propname))
+                    {
+                        extensionData ??= new(4);
+                        extensionData.Add(new(propname, propvalue));
+                    }
+
+                    break;
+                }
+                case JsonTokenType.Comment: break;
+                case JsonTokenType.EndObject: goto endLoop;
+                default: throw new JsonException("Unable to deserialize Error type.");
+            }
+        }
+        endLoop:
+        return (type, message, extensionData?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty);
+    }
+    internal static void WriteOne(Utf8JsonWriter writer, Error value)
+    {
+        writer.WriteStartObject();
+
+        writer.WriteString("type", value.Type);
+        writer.WriteString("msg", value.Message);
+
+        if (value.ExtensionData?.Count > 0)
+        {
+            foreach (var (key, val) in value.ExtensionData)
+            {
+                writer.WriteString(key, val);
+            }
+        }
+
+        writer.WriteEndObject();
+    }
+}
+
+public sealed class ExpectedErrorJsonConverter : JsonConverter<ExpectedError>
+{
+    public override ExpectedError? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartObject => ErrorJsonConverter.ToExpectedError(ErrorJsonConverter.ReadOne(ref reader)),
+            JsonTokenType.None => null,
+            JsonTokenType.Null => null,
+            _ => throw new JsonException("Unexpected JSON token.")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, ExpectedError value, JsonSerializerOptions options)
+    {
+        ErrorJsonConverter.WriteOne(writer, value);
+    }
+}
+
+public sealed class ExceptionalErrorJsonConverter : JsonConverter<ExceptionalError>
+{
+    public override ExceptionalError? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartObject => ToExceptionalError(ErrorJsonConverter.ReadOne(ref reader)),
+            JsonTokenType.None => null,
+            JsonTokenType.Null => null,
+            _ => throw new JsonException("Unexpected JSON token.")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, ExceptionalError value, JsonSerializerOptions options)
+    {
+        ErrorJsonConverter.WriteOne(writer, value);
+    }
+
+    private static ExceptionalError ToExceptionalError(in (string Type, string Message, ImmutableDictionary<string, string> ExtensionData) errorInfo)
+        => new(errorInfo.Type, errorInfo.Message) { ExtensionData = errorInfo.ExtensionData };
+}
+
+public sealed class ManyErrorsJsonConverter : JsonConverter<ManyErrors>
+{
+    public override ManyErrors? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartArray => ErrorJsonConverter.ReadMany(ref reader),
+            JsonTokenType.None => null,
+            JsonTokenType.Null => null,
+            _ => throw new JsonException("Unexpected JSON token.")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, ManyErrors value, JsonSerializerOptions options)
+    {
+        writer.WriteStartArray();
+        foreach (var err in value)
+        {
+            ErrorJsonConverter.WriteOne(writer, err);
+        }
+        writer.WriteEndArray();
+    }
+}

Railway/Railway.csproj

@@ -1,16 +1,20 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
+    <LangVersion>10.0</LangVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <AssemblyName>Just.Railway</AssemblyName>
     <RootNamespace>Just.Railway</RootNamespace>
     
+    <Description>Base for railway-oriented programming in .NET. Package includes Result object, Error class and most of the common extensions.</Description>
+    <PackageTags>railway-oriented;functional;result-pattern;result-object;error-handling</PackageTags>
     <Authors>JustFixMe</Authors>
     <Copyright>Copyright (c) 2023 JustFixMe</Copyright>
-    <PackageLicenseExpression>MIT</PackageLicenseExpression>
-    <RepositoryUrl>https://gitea.jstdev.ru/just/Just.Railway/</RepositoryUrl>
+    <PackageLicenseFile>LICENSE</PackageLicenseFile>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
+    <RepositoryUrl>https://github.com/JustFixMe/Just.Railway/</RepositoryUrl>
     
     <EmitCompilerGeneratedFiles Condition="'$(Configuration)'=='Debug'">true</EmitCompilerGeneratedFiles>
     <ReleaseVersion Condition=" '$(ReleaseVersion)' == '' ">1.0.0</ReleaseVersion>
@@ -24,6 +28,11 @@
     <InternalsVisibleTo Include="$(AssemblyName).Tests" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Include="..\README.md" Pack="true" PackagePath=""/>
+    <None Include="..\LICENSE" Pack="true" Visible="false" PackagePath=""/>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\Railway.SourceGenerator\Railway.SourceGenerator.csproj"
                       OutputItemType="Analyzer"

Railway/ReflectionHelper.cs

@@ -10,10 +10,9 @@ internal static class ReflectionHelper
 
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static int Compare<T>(T? left, T? right) => TypeReflectionCache<T>.CompareFunc(left, right);
-}
 
-file static class TypeReflectionCache<T>
-{
+    private static class TypeReflectionCache<T>
+    {
         public static readonly Func<T?, T?, bool> IsEqualFunc;
         public static readonly Func<T?, T?, int> CompareFunc;
 
@@ -53,7 +52,7 @@ file static class TypeReflectionCache<T>
             }
         }
 
-#pragma warning disable CS8604 // Possible null reference argument.
+    #pragma warning disable CS8604 // Possible null reference argument.
         [Pure] public static bool IsEqual<R>(R? left, R? right) where R : notnull, IEquatable<R>, T => left is null ? right is null : left.Equals(right);
         [Pure] public static bool IsEqualNullable<R>(R? left, R? right) where R : struct, IEquatable<R> => left is null ? right is null : right is not null && left.Value.Equals(right.Value);
 
@@ -63,5 +62,6 @@ file static class TypeReflectionCache<T>
         [Pure] public static int CompareNullable<R>(R? left, R? right) where R : struct, IComparable<R> => left is null
             ? right is null ? 0 : -1
             : right is null ? 1 : left.Value.CompareTo(right.Value);
-#pragma warning restore CS8604 // Possible null reference argument.
+    #pragma warning restore CS8604 // Possible null reference argument.
+    }
 }

Railway/Result.cs

@@ -136,6 +136,7 @@ public readonly struct Result<T> : IEquatable<Result<T>>
     {
         Value = value;
         State = ResultState.Success;
+        Error = default;
     }
 
     [Pure] public static explicit operator Result(Result<T> result) => result.State switch
@@ -263,7 +264,12 @@ public readonly struct SuccessUnit : IEquatable<SuccessUnit>
 }
 
 [Serializable]
-public class ResultNotInitializedException(string variableName = "this") : InvalidOperationException("Result was not properly initialized.")
+public class ResultNotInitializedException : InvalidOperationException
 {
-    public string VariableName { get; } = variableName;
+    public ResultNotInitializedException(string variableName = "this")
+        : base("Result was not properly initialized.")
+    {
+        VariableName = variableName;
+    }
+    public string VariableName { get; }
 }

Railway/ResultExtensions.cs

@@ -2,6 +2,80 @@ namespace Just.Railway;
 
 public static partial class ResultExtensions
 {
+    #region Match (with fallback)
+    
+    public static T Match<T>(this in Result<T> result, Func<Error, T> fallback)
+    {
+        return result.State switch
+        {
+            ResultState.Success => result.Value,
+            ResultState.Error => fallback(result.Error!),
+            _ => throw new ResultNotInitializedException(nameof(result))
+        };
+    }
+    
+    public static async Task<T> Match<T>(this Result<T> result, Func<Error, Task<T>> fallback)
+    {
+        return result.State switch
+        {
+            ResultState.Success => result.Value,
+            ResultState.Error => await fallback(result.Error!).ConfigureAwait(false),
+            _ => throw new ResultNotInitializedException(nameof(result))
+        };
+    }
+    public static async Task<T> Match<T>(this Task<Result<T>> resultTask, Func<Error, T> fallback)
+    {
+        var result = await resultTask.ConfigureAwait(false);
+        return result.State switch
+        {
+            ResultState.Success => result.Value,
+            ResultState.Error => fallback(result.Error!),
+            _ => throw new ResultNotInitializedException(nameof(resultTask))
+        };
+    }
+    public static async Task<T> Match<T>(this Task<Result<T>> resultTask, Func<Error, Task<T>> fallback)
+    {
+        var result = await resultTask.ConfigureAwait(false);
+        return result.State switch
+        {
+            ResultState.Success => result.Value,
+            ResultState.Error => await fallback(result.Error!).ConfigureAwait(false),
+            _ => throw new ResultNotInitializedException(nameof(resultTask))
+        };
+    }
+
+    public static async ValueTask<T> Match<T>(this Result<T> result, Func<Error, ValueTask<T>> fallback)
+    {
+        return result.State switch
+        {
+            ResultState.Success => result.Value,
+            ResultState.Error => await fallback(result.Error!).ConfigureAwait(false),
+            _ => throw new ResultNotInitializedException(nameof(result))
+        };
+    }
+    public static async ValueTask<T> Match<T>(this ValueTask<Result<T>> resultTask, Func<Error, T> fallback)
+    {
+        var result = await resultTask.ConfigureAwait(false);
+        return result.State switch
+        {
+            ResultState.Success => result.Value,
+            ResultState.Error => fallback(result.Error!),
+            _ => throw new ResultNotInitializedException(nameof(resultTask))
+        };
+    }
+    public static async ValueTask<T> Match<T>(this ValueTask<Result<T>> resultTask, Func<Error, ValueTask<T>> fallback)
+    {
+        var result = await resultTask.ConfigureAwait(false);
+        return result.State switch
+        {
+            ResultState.Success => result.Value,
+            ResultState.Error => await fallback(result.Error!).ConfigureAwait(false),
+            _ => throw new ResultNotInitializedException(nameof(resultTask))
+        };
+    }
+
+    #endregion
+    
     #region Merge
 
     public static Result Merge(this IEnumerable<Result> results)
@@ -15,7 +89,7 @@ public static partial class ResultExtensions
             {
                 case ResultState.Error:
                     hasErrors = true;
-                    errors ??= [];
+                    errors ??= new(4);
                     errors.Add(result.Error!);
                     break;
 
@@ -49,13 +123,13 @@ public static partial class ResultExtensions
             {
                 case ResultState.Error:
                     hasErrors = true;
-                    errors ??= [];
+                    errors ??= new(4);
                     errors.Add(result.Error!);
                     break;
 
                 case ResultState.Success:
                     if (hasErrors) goto afterLoop;
-                    values ??= [];
+                    values ??= new(4);
                     values.Add(result.Value);
                     break;
                     

Raliway.Tests/Errors/Serialization.cs

@@ -6,40 +6,71 @@ public class Serialization
     public void WhenSerializingManyErrors()
     {
         // Given
-        Error many_errors = new ManyErrors(new Error[]{
-            new ExpectedError("err1", "msg1"){
-                ExtensionData = {
-                    ["ext"] = "ext_value"
-                }
-            },
-            new ExceptionalError(new Exception("msg2")),
-        });
+        Error many_errors = new ManyErrors(
+        [
+            Error.New("err1", "msg1", new KeyValuePair<string, string>[]
+            {
+                new("ext", "ext_value"),
+            }),
+            Error.New(new Exception("msg2")),
+        ]);
         // When
         var result = JsonSerializer.Serialize(many_errors);
         // Then
         Assert.Equal(
-            expected: "[{\"$$err\":0,\"Type\":\"err1\",\"Message\":\"msg1\",\"ext\":\"ext_value\"},{\"$$err\":1,\"Type\":\"Exception\",\"Message\":\"msg2\"}]",
+            expected: "[{\"type\":\"err1\",\"msg\":\"msg1\",\"ext\":\"ext_value\"},{\"type\":\"System.Exception\",\"msg\":\"msg2\"}]",
             result);
     }
 
     [Fact]
-    public void WhenDeserializingManyErrors()
+    public void WhenDeserializingManyErrorsAsError()
     {
         // Given
-        var json = "[{\"$$err\":0,\"Type\":\"err1\",\"Message\":\"msg1\",\"ext\":\"ext_value\"},{\"$$err\":1,\"Type\":\"Exception\",\"Message\":\"msg2\"}]";
+        var json = "[{\"type\":\"err1\",\"msg\":\"msg1\",\"ext1\":\"ext_value1\",\"ext2\":\"ext_value2\"},{\"type\":\"System.Exception\",\"msg\":\"msg2\"}]";
         // When
-        var result = JsonSerializer.Deserialize<Error[]>(json);
+        var result = JsonSerializer.Deserialize<Error>(json);
         // Then
-        Assert.True(result?.Length == 2);
+        Assert.IsType<ManyErrors>(result);
+        ManyErrors manyErrors = (ManyErrors)result;
+
+        Assert.True(manyErrors.Count == 2);
         Assert.Equal(
-            expected: new ManyErrors(new Error[]{
-                new ExpectedError("err1", "msg1"),
-                new ExceptionalError(new Exception("msg2")),
-            }),
+            expected: Error.Many(
+                Error.New("err1", "msg1"),
+                Error.New(new Exception("msg2"))
+            ).ToEnumerable(),
+            manyErrors
+        );
+        Assert.Equal(
+            expected: "ext_value1",
+            manyErrors[0]["ext1"]);
+        Assert.Equal(
+            expected: "ext_value2",
+            manyErrors[0]["ext2"]);
+    }
+
+    [Fact]
+    public void WhenDeserializingManyErrorsAsManyErrors()
+    {
+        // Given
+        var json = "[{\"type\":\"err1\",\"msg\":\"msg1\",\"ext1\":\"ext_value1\",\"ext2\":\"ext_value2\"},{\"type\":\"System.Exception\",\"msg\":\"msg2\"}]";
+        // When
+        var result = JsonSerializer.Deserialize<ManyErrors>(json);
+        // Then
+        Assert.NotNull(result);
+        Assert.True(result.Count == 2);
+        Assert.Equal(
+            expected: Error.Many(
+                Error.New("err1", "msg1"),
+                Error.New(new Exception("msg2"))
+            ).ToEnumerable(),
             result
         );
         Assert.Equal(
-            expected: "ext_value",
-            result[0].ExtensionData["ext"].ToString());
+            expected: "ext_value1",
+            result[0]["ext1"]);
+        Assert.Equal(
+            expected: "ext_value2",
+            result[0]["ext2"]);
     }
 }

Raliway.Tests/Results/Combine.cs

@@ -0,0 +1,78 @@
+namespace Raliway.Tests.Results;
+
+public class Combine
+{
+    [Fact]
+    public void TwoResultCombination_WhenThereIsAnError()
+    {
+        // Given
+        var result1 = Result.Success(1);
+        var result2 = Result.Failure(Error.New("some error"));
+        // When
+        var result = Result.Combine(result1, result2);
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(result2.Error, result.Error);
+    }
+    [Fact]
+    public void TwoResultCombination_WhenThereAreTwoErrors()
+    {
+        // Given
+        var result1 = Result.Failure<byte>(Error.New("1"));
+        var result2 = Result.Failure(Error.New("2"));
+        // When
+        var result = Result.Combine(result1, result2);
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(result1.Error + result2.Error, result.Error);
+    }
+    [Fact]
+    public void TwoResultCombination_WhenThereIsNoError()
+    {
+        // Given
+        var result1 = Result.Success(1);
+        var result2 = Result.Success(3.14);
+        // When
+        var result = Result.Combine(result1, result2);
+        // Then
+        Assert.True(result.IsSuccess);
+    }
+    [Fact]
+    public void ThreeResultCombination_WhenThereIsAnError()
+    {
+        // Given
+        var result1 = Result.Success(1);
+        var result2 = Result.Success(3.14);
+        var result3 = Result.Failure(Error.New("some error"));
+        // When
+        Result<(int, double)> result = Result.Combine(result1, result2, result3);
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(result3.Error, result.Error);
+    }
+    [Fact]
+    public void ThreeResultCombination_WhenThereAreTwoErrors()
+    {
+        // Given
+        var result1 = Result.Failure<int?>(Error.New("1"));
+        var result2 = Result.Success(3.14);
+        var result3 = Result.Failure(Error.New("3"));
+        // When
+        Result<(int?, double)> result = Result.Combine(result1, result2, result3);
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(result1.Error + result3.Error, result.Error);
+    }
+    [Fact]
+    public void ThreeResultCombination_WhenThereIsNoError()
+    {
+        // Given
+        var result1 = Result.Success(1);
+        var result2 = Result.Success(3.14);
+        var result3 = Result.Success();
+        // When
+        var result = Result.Combine(result1, result2, result3);
+        // Then
+        Assert.True(result.IsSuccess);
+    }
+}

Raliway.Tests/Results/GeneralUsage.cs

@@ -2,80 +2,6 @@ namespace Raliway.Tests.Results;
 
 public class GeneralUsage
 {
-    [Fact]
-    public void TwoResultCombination_WhenThereIsAnError()
-    {
-        // Given
-        var result1 = Result.Success(1);
-        var result2 = Result.Failure(Error.New("some error"));
-        // When
-        var result = Result.Combine(result1, result2);
-        // Then
-        Assert.True(result.IsFailure);
-        Assert.Equal(result2.Error, result.Error);
-    }
-    [Fact]
-    public void TwoResultCombination_WhenThereAreTwoErrors()
-    {
-        // Given
-        var result1 = Result.Failure<byte>(Error.New("1"));
-        var result2 = Result.Failure(Error.New("2"));
-        // When
-        var result = Result.Combine(result1, result2);
-        // Then
-        Assert.True(result.IsFailure);
-        Assert.Equal(result1.Error + result2.Error, result.Error);
-    }
-    [Fact]
-    public void TwoResultCombination_WhenThereIsNoError()
-    {
-        // Given
-        var result1 = Result.Success(1);
-        var result2 = Result.Success(3.14);
-        // When
-        var result = Result.Combine(result1, result2);
-        // Then
-        Assert.True(result.IsSuccess);
-    }
-    [Fact]
-    public void ThreeResultCombination_WhenThereIsAnError()
-    {
-        // Given
-        var result1 = Result.Success(1);
-        var result2 = Result.Success(3.14);
-        var result3 = Result.Failure(Error.New("some error"));
-        // When
-        Result<(int, double)> result = Result.Combine(result1, result2, result3);
-        // Then
-        Assert.True(result.IsFailure);
-        Assert.Equal(result3.Error, result.Error);
-    }
-    [Fact]
-    public void ThreeResultCombination_WhenThereAreTwoErrors()
-    {
-        // Given
-        var result1 = Result.Failure<int?>(Error.New("1"));
-        var result2 = Result.Success(3.14);
-        var result3 = Result.Failure(Error.New("3"));
-        // When
-        Result<(int?, double)> result = Result.Combine(result1, result2, result3);
-        // Then
-        Assert.True(result.IsFailure);
-        Assert.Equal(result1.Error + result3.Error, result.Error);
-    }
-    [Fact]
-    public void ThreeResultCombination_WhenThereIsNoError()
-    {
-        // Given
-        var result1 = Result.Success(1);
-        var result2 = Result.Success(3.14);
-        var result3 = Result.Success();
-        // When
-        var result = Result.Combine(result1, result2, result3);
-        // Then
-        Assert.True(result.IsSuccess);
-    }
-
     [Fact]
     public void ChainedResultExtensions_WhenThereIsNoError()
     {
@@ -104,10 +30,9 @@ public class GeneralUsage
     public void ChainedResultExtensions_WhenThereIsAnError()
     {
         // Given
-        
-        // When
         var error = Error.New("test");
         
+        // When
 
         var result = Result.Success()
             .Append(() => Result.Failure<int>(error))
@@ -115,7 +40,7 @@ public class GeneralUsage
             .Map((i, s) =>
             {
                 Assert.Fail();
-                return Result.Success("");
+                return "";
             })
             .Append("some")
             .Bind((s1, s2) => 
@@ -139,4 +64,68 @@ public class GeneralUsage
         // Then
         Assert.Equal("satisfied", result);
     }
+
+    [Fact]
+    public async Task ChainedResultAsyncExtensions_WhenThereIsNoError()
+    {
+        // Given
+
+        // When
+        var result = await Result.Success()
+            .Append(() => ValueTask.FromResult(Result.Success(1)))
+            .Append("test")
+            .Map((i, s) => $"{s}_{i}")
+            .Append("some")
+            .Bind(async (s1, s2) => await ValueTask.FromResult(Result.Success(string.Join(';', s1, s2))))
+            .Match(
+                onSuccess: s => s.ToUpper(),
+                onFailure: _ =>
+                {
+                    Assert.Fail();
+                    return "";
+                }
+            );
+        
+        Assert.Equal("TEST_1;SOME", result);
+    }
+
+    [Fact]
+    public async Task ChainedResultAsyncExtensions_WhenThereIsAnError()
+    {
+        // Given
+        var error = Error.New("test");
+        
+        // When
+
+        var result = await Result.Success()
+            .Append(() => Task.FromResult(Result.Failure<int>(error)))
+            .Append("test")
+            .Map((i, s) =>
+            {
+                Assert.Fail();
+                return "";
+            })
+            .Append("some")
+            .Bind(async (s1, s2) => 
+            {
+                Assert.Fail();
+                await Task.CompletedTask;
+                return Result.Success("");
+            })
+            .Match(
+                onSuccess: _ => 
+                {
+                    Assert.Fail();
+                    return "";
+                },
+                onFailure: err =>
+                {
+                    Assert.Equal(error, err);
+                    return "satisfied";
+                }
+            );
+
+        // Then
+        Assert.Equal("satisfied", result);
+    }
 }