extended recover tests

.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

@@ -14,13 +14,11 @@ The desire is to make somewhat user-friendly experience while using result-objec
 
 ## Getting Started
 
-### Install from local Gitea package repository
+### Install from NuGet.org
 
 ```sh
-# Setup NuGet registry from the command line
+# install the package using NuGet
-dotnet nuget add source --name gitea_jstdev https://gitea.jstdev.ru/api/packages/just/nuget/index.json
+dotnet add package Just.Railway
-# then install the package using NuGet
-dotnet add package --source gitea_jstdev Just.Railway
 ```
 
 ## Examples
@@ -71,9 +69,9 @@ Result<T> Bar()
 ```csharp
 Result<int> result = GetResult();
 
-var value = result
+string value = result
-    .Append("new")
+    .Append("new") // -> Result<(int, string)>
-    .Map((i, s) => $"{s} result {i}")
+    .Map((i, s) => $"{s} result {i}") // -> Result<string>
     .Match(
         onSuccess: x => x,
         onFailure: err => err.ToString()
@@ -83,6 +81,17 @@ var value = result
 Result<int> GetResult() => Result.Success(1);
 ```
 
+#### Recover from failure
+
+```csharp
+Result<string> failed = new NotImplementedException();
+
+Result<string> result = failed.TryRecover(err => err.Type == "System.NotImplementedException"
+    ? "recovered"
+    : err);
+// result with value: "recovered"
+```
+
 ### Try
 
 ```csharp
@@ -101,9 +110,9 @@ int SomeFunction() => 1;
 ### Ensure
 
 ```csharp
-var value = GetValue();
+int? value = GetValue();
-Result<int> result = Ensure.That(value)
+Result<int> result = Ensure.That(value) // -> Ensure<int?>
-    .NotNull()
+    .NotNull() // -> Ensure<int>
     .Satisfies(i => i < 100)
     .Result();
 

Railway.SourceGenerator/EnsureExtensionsExecutor.cs

@@ -41,22 +41,46 @@ public sealed class EnsureExtensionsExecutor : IGeneratorExecutor
 
         var sb = new StringBuilder();
 
-        sb.AppendLine($"#region Satisfies");
+        sb.AppendLine("#region Satisfies");
         errorGenerationDefinitions.ForEach(def => GenerateSatisfiesExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
         sb.AppendLine("#endregion");
 
-        sb.AppendLine($"#region NotNull");
+        sb.AppendLine("#region NotNull");
         errorGenerationDefinitions.ForEach(def => GenerateNotNullExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
         sb.AppendLine("#endregion");
 
-        sb.AppendLine($"#region NotEmpty");
+        sb.AppendLine("#region NotEmpty");
         errorGenerationDefinitions.ForEach(def => GenerateNotEmptyExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
         sb.AppendLine("#endregion");
 
+        sb.AppendLine("#region NotWhitespace");
+        errorGenerationDefinitions.ForEach(def => GenerateNotWhitespaceExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
 
         return sb.ToString();
     }
 
+    private void GenerateNotWhitespaceExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is empty or consists exclusively of white-space characters.\")";
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<string> NotWhitespace(this in Ensure<string> ensure, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => string.IsNullOrWhiteSpace(ensure.Value)
+                    ? new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression)
+                    : new(ensure.Value!, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
     private void GenerateNotEmptyExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
     {
         string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is empty.\")";

Railway.SourceGenerator/ExtensionsMethodGenerator.cs

@@ -17,6 +17,7 @@ public class ExtensionsMethodGenerator : IIncrementalGenerator
         new ResultMapExecutor(),
         new ResultBindExecutor(),
         new ResultTapExecutor(),
+        new ResultTryRecoverExecutor(),
         new ResultAppendExecutor(),
         new TryExtensionsExecutor(),
         new EnsureExtensionsExecutor(),

Railway.SourceGenerator/ResultTryRecoverExecutor.cs

@@ -0,0 +1,86 @@
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+using Microsoft.CodeAnalysis;
+
+namespace Just.Railway.SourceGen;
+
+internal sealed class ResultTryRecoverExecutor : ResultExtensionsExecutor
+{
+    protected override string ExtensionType => "TryRecover";
+    protected override void GenerateMethodsForArgCount(StringBuilder sb, int argCount)
+    {
+        if (argCount > 1) return;
+        
+        var templateArgNames = Enumerable.Repeat("T", argCount)
+            .ToImmutableArray();
+
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames);
+        string resultTypeDef = GenerateResultTypeDef(templateArgNames);
+
+        sb.AppendLine($"#region {resultTypeDef}");
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTryRecoverExecutor)}}", "1.0.0.0")]
+        public static {{resultTypeDef}} TryRecover{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Func<Error, {{resultTypeDef}}> recover)
+        {
+            return result.State switch
+            {
+                ResultState.Success => ({{resultTypeDef}})result.Value,
+                ResultState.Error => recover(result.Error!),
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        GenerateAsyncMethods("Task", sb, templateArgNames, resultTypeDef, methodTemplateDecl);
+        GenerateAsyncMethods("ValueTask", sb, templateArgNames, resultTypeDef, methodTemplateDecl);
+
+        sb.AppendLine("#endregion");
+    }
+    private static void GenerateAsyncMethods(string taskType, StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string methodTemplateDecl)
+    {
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTryRecoverExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> TryRecover{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<Error, {{resultTypeDef}}> recover)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => ({{resultTypeDef}})result.Value,
+                ResultState.Error => recover(result.Error!),
+                _ => throw new ResultNotInitializedException(nameof(resultTask))
+            };
+        }
+        """);
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTryRecoverExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> TryRecover{{methodTemplateDecl}}(this {{resultTypeDef}} result, Func<Error, {{taskType}}<{{resultTypeDef}}>> recover)
+        {
+            return result.State switch
+            {
+                ResultState.Success => ({{resultTypeDef}})result.Value,
+                ResultState.Error => await recover(result.Error!).ConfigureAwait(false),
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTryRecoverExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> TryRecover{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<Error, {{taskType}}<{{resultTypeDef}}>> recover)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => ({{resultTypeDef}})result.Value,
+                ResultState.Error => await recover(result.Error!).ConfigureAwait(false),
+                _ => throw new ResultNotInitializedException(nameof(resultTask))
+            };
+        }
+        """);
+    }
+}

Railway/Ensure.cs

@@ -34,18 +34,6 @@ public static partial class Ensure
             _ => throw new EnsureNotInitializedException(nameof(ensureTask))
         };
     }
-
-    [Pure] public static Ensure<string> NotWhitespace(this in Ensure<string> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => string.IsNullOrWhiteSpace(ensure.Value)
-                ? new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty or consists exclusively of white-space characters."), ensure.ValueExpression)
-                : new(ensure.Value, ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
 }
 
 public readonly struct Ensure<T>
@@ -60,6 +48,7 @@ public readonly struct Ensure<T>
         Value = value;
         ValueExpression = valueExpression;
         State = ResultState.Success;
+        Error = default;
     }
 
     internal Ensure(Error error, string valueExpression)
@@ -72,7 +61,12 @@ 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

@@ -1,14 +1,10 @@
 using System.Collections;
 using System.Collections.Immutable;
-using System.Runtime.Serialization;
 using System.Text;
 
 namespace Just.Railway;
 
-[JsonPolymorphic(TypeDiscriminatorPropertyName = "$$err")]
+[JsonConverter(typeof(ErrorJsonConverter))]
-[JsonDerivedType(typeof(ExpectedError), typeDiscriminator: 0)]
-[JsonDerivedType(typeof(ExceptionalError), typeDiscriminator: 1)]
-[JsonDerivedType(typeof(ManyErrors))]
 public abstract class Error : IEquatable<Error>, IComparable<Error>
 {
     protected internal Error(){}
@@ -33,16 +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) =>
+    public static Error New(string message, IEnumerable<KeyValuePair<string, string>>? extensionData = null) =>
-        new ExpectedError("error", message);
+        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) =>
+    public static Error New(string type, string message, IEnumerable<KeyValuePair<string, string>>? extensionData = null) =>
-        new ExpectedError(type, message);
+        new ExpectedError(type, message)
+        {
+            ExtensionData = extensionData?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty
+        };
     /// <summary>
     /// Create a <see cref="ManyErrors"/>
     /// </summary>
@@ -50,7 +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,
@@ -76,13 +78,14 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
 
     [Pure] public abstract string Type { get; }
     [Pure] public abstract string Message { get; }
-    [Pure, JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)] public ImmutableDictionary<string, string>? ExtensionData { get; init; }
-    [Pure] public string? this[string key] => ExtensionData?.TryGetValue(key, out var value) == true ? value : null;
 
-    [Pure, JsonIgnore] public abstract int Count { get; }
+    [Pure] public ImmutableDictionary<string, string> ExtensionData { get; internal init; } = ImmutableDictionary<string, string>.Empty;
-    [Pure, JsonIgnore] public abstract bool IsEmpty { get; }
+    [Pure] public string? this[string key] => ExtensionData.TryGetValue(key, out var value) == true ? value : null;
-    [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)
     {
@@ -142,9 +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;
@@ -158,10 +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] public override int Count => 1;
-    [Pure, JsonIgnore] public override bool IsEmpty => false;
+    [Pure] public override bool IsEmpty => false;
-    [Pure, JsonIgnore] public override bool IsExpected => true;
+    [Pure] public override bool IsExpected => true;
-    [Pure, JsonIgnore] public override bool IsExeptional => false;
+    [Pure] public override bool IsExeptional => false;
 
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public override IEnumerable<Error> ToEnumerable()
@@ -170,24 +173,27 @@ public sealed class ExpectedError : Error
     }
 }
 
+[JsonConverter(typeof(ExceptionalErrorJsonConverter))]
 public sealed class ExceptionalError : Error
 {
     internal readonly Exception? Exception;
 
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    internal static string ToErrorType(Type exceptionType) => exceptionType.FullName ?? exceptionType.Name;
+
     internal ExceptionalError(Exception exception)
-        : this(exception.GetType().Name, exception.Message)
+        : this(ToErrorType(exception.GetType()), exception.Message)
     {
         Exception = exception;
         ExtensionData = ExtractExtensionData(exception);
     }
     internal ExceptionalError(string message, Exception exception)
-        : this(exception.GetType().Name, message)
+        : this(ToErrorType(exception.GetType()), message)
     {
         Exception = exception;
         ExtensionData = ExtractExtensionData(exception);
     }
 
-    [JsonConstructor]
     public ExceptionalError(string type, string message)
     {
         Type = type;
@@ -197,10 +203,10 @@ 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] public override int Count => 1;
-    [Pure, JsonIgnore] public override bool IsEmpty => false;
+    [Pure] public override bool IsEmpty => false;
-    [Pure, JsonIgnore] public override bool IsExpected => false;
+    [Pure] public override bool IsExpected => false;
-    [Pure, JsonIgnore] public override bool IsExeptional => true;
+    [Pure] public override bool IsExeptional => true;
 
     [Pure] public override Exception ToException() => Exception ?? base.ToException();
 
@@ -210,10 +216,10 @@ public sealed class ExceptionalError : Error
         yield return this;
     }
 
-    private static ImmutableDictionary<string, string>? ExtractExtensionData(Exception exception)
+    private static ImmutableDictionary<string, string> ExtractExtensionData(Exception exception)
     {
         if (!(exception.Data?.Count > 0))
-        return null;
+        return ImmutableDictionary<string, string>.Empty;
 
         List<KeyValuePair<string, string>>? values = null;
 
@@ -228,19 +234,20 @@ public sealed class ExceptionalError : Error
             var valueString = value.ToString();
             if (string.IsNullOrEmpty(keyString) || string.IsNullOrEmpty(valueString)) continue;
 
-            values ??= [];
+            values ??= new List<KeyValuePair<string, string>>(4);
             values.Add(new(keyString, valueString));
         }
-        return values?.ToImmutableDictionary();
+        return values?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty;
     }
 }
 
-[DataContract]
+[JsonConverter(typeof(ManyErrorsJsonConverter))]
-public sealed class ManyErrors : Error, IEnumerable<Error>
+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);
@@ -283,9 +290,11 @@ public sealed class ManyErrors : Error, IEnumerable<Error>
     }
 
     [Pure] public override int Count => _errors.Count;
-    [Pure, JsonIgnore] public override bool IsEmpty => _errors.Count == 0;
+    [Pure] public override bool IsEmpty => _errors.Count == 0;
-    [Pure, JsonIgnore] public override bool IsExpected => _errors.All(static x => x.IsExpected);
+    [Pure] 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 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;
@@ -371,7 +380,11 @@ 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>
+    <PackageLicenseFile>LICENSE</PackageLicenseFile>
-    <RepositoryUrl>https://gitea.jstdev.ru/just/Just.Railway/</RepositoryUrl>
+    <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

@@ -10,58 +10,58 @@ 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;
-
-    static TypeReflectionCache()
     {
-        var type = typeof(T);
+        public static readonly Func<T?, T?, bool> IsEqualFunc;
-        var isNullableStruct = type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>);
+        public static readonly Func<T?, T?, int> CompareFunc;
-        var underlyingType = isNullableStruct ? type.GenericTypeArguments.First() : type;
-        var thisType = typeof(TypeReflectionCache<T>);
 
-        var equatableType = typeof(IEquatable<>).MakeGenericType(underlyingType);
+        static TypeReflectionCache()
-        if (equatableType.IsAssignableFrom(underlyingType))
         {
-            var isEqualFunc = thisType.GetMethod(isNullableStruct ? nameof(IsEqualNullable) : nameof(IsEqual), BindingFlags.Static | BindingFlags.Public)
+            var type = typeof(T);
-                !.MakeGenericMethod(underlyingType);
+            var isNullableStruct = type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>);
+            var underlyingType = isNullableStruct ? type.GenericTypeArguments.First() : type;
+            var thisType = typeof(TypeReflectionCache<T>);
 
-            IsEqualFunc = (Func<T?, T?, bool>)Delegate.CreateDelegate(typeof(Func<T?, T?, bool>), isEqualFunc);
+            var equatableType = typeof(IEquatable<>).MakeGenericType(underlyingType);
-        }
+            if (equatableType.IsAssignableFrom(underlyingType))
-        else
+            {
-        {
+                var isEqualFunc = thisType.GetMethod(isNullableStruct ? nameof(IsEqualNullable) : nameof(IsEqual), BindingFlags.Static | BindingFlags.Public)
-            IsEqualFunc = static (left, right) => left is null ? right is null : left.Equals(right);
+                    !.MakeGenericMethod(underlyingType);
+
+                IsEqualFunc = (Func<T?, T?, bool>)Delegate.CreateDelegate(typeof(Func<T?, T?, bool>), isEqualFunc);
+            }
+            else
+            {
+                IsEqualFunc = static (left, right) => left is null ? right is null : left.Equals(right);
+            }
+
+            var comparableType = typeof(IComparable<>).MakeGenericType(underlyingType);
+            if (comparableType.IsAssignableFrom(underlyingType))
+            {
+                var compareFunc = thisType.GetMethod(isNullableStruct ? nameof(CompareNullable) : nameof(Compare), BindingFlags.Static | BindingFlags.Public)
+                    !.MakeGenericMethod(underlyingType);
+
+                CompareFunc = (Func<T?, T?, int>)Delegate.CreateDelegate(typeof(Func<T?, T?, int>), compareFunc);
+            }
+            else
+            {
+                CompareFunc = static (left, right) => left is null
+                    ? right is null ? 0 : -1
+                    : right is null ? 1 : left.GetHashCode().CompareTo(right.GetHashCode());
+            }
         }
 
-        var comparableType = typeof(IComparable<>).MakeGenericType(underlyingType);
+    #pragma warning disable CS8604 // Possible null reference argument.
-        if (comparableType.IsAssignableFrom(underlyingType))
+        [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);
-            var compareFunc = thisType.GetMethod(isNullableStruct ? nameof(CompareNullable) : nameof(Compare), BindingFlags.Static | BindingFlags.Public)
-                !.MakeGenericMethod(underlyingType);
 
-            CompareFunc = (Func<T?, T?, int>)Delegate.CreateDelegate(typeof(Func<T?, T?, int>), compareFunc);
+        [Pure] public static int Compare<R>(R? left, R? right) where R : notnull, IComparable<R>, T => left is null
-        }
+            ? right is null ? 0 : -1
-        else
+            : right is null ? 1 : left.CompareTo(right);
-        {
+        [Pure] public static int CompareNullable<R>(R? left, R? right) where R : struct, IComparable<R> => left is null
-            CompareFunc = static (left, right) => left is null
+            ? right is null ? 0 : -1
-                ? right is null ? 0 : -1
+            : right is null ? 1 : left.Value.CompareTo(right.Value);
-                : right is null ? 1 : left.GetHashCode().CompareTo(right.GetHashCode());
+    #pragma warning restore 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);
-
-    [Pure] public static int Compare<R>(R? left, R? right) where R : notnull, IComparable<R>, T => left is null
-        ? right is null ? 0 : -1
-        : right is null ? 1 : left.CompareTo(right);
-    [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.
 }

Railway/Result.cs

@@ -8,6 +8,7 @@ internal enum ResultState : byte
 
 public readonly partial struct Result : IEquatable<Result>
 {
+    internal SuccessUnit Value => new();
     internal readonly Error? Error;
     internal readonly ResultState State;
 
@@ -51,13 +52,18 @@ public readonly partial struct Result : IEquatable<Result>
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static implicit operator Result(Error error) => new(error ?? throw new ArgumentNullException(nameof(error)));
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator Result(Exception exception) => new(
+        new ExceptionalError(exception ?? throw new ArgumentNullException(nameof(exception))));
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static implicit operator Result<SuccessUnit>(Result result) => result.State switch
     {
         ResultState.Success => new(new SuccessUnit()),
         ResultState.Error => new(result.Error!),
         _ => throw new ResultNotInitializedException(nameof(result))
     };
-    
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static explicit operator Result(SuccessUnit _) => new(null);
+
     [Pure] public bool IsSuccess => Error is null;
     [Pure] public bool IsFailure => Error is not null;
 
@@ -136,16 +142,23 @@ 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
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static explicit operator Result(Result<T> result) => result.State switch
     {
         ResultState.Success => new(null),
         ResultState.Error => new(result.Error!),
         _ => throw new ResultNotInitializedException(nameof(result))
     };
-    [Pure] public static implicit operator Result<T>(Error error) => new(error);
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
-    [Pure] public static implicit operator Result<T>(T value) => new(value);
+    public static implicit operator Result<T>(Error error) => new(error);
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator Result<T>(Exception exception) => new(
+        new ExceptionalError(exception ?? throw new ArgumentNullException(nameof(exception))));
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator Result<T>(T value) => new(value);
     [Pure] public bool IsSuccess => State == ResultState.Success;
     [Pure] public bool IsFailure => State == ResultState.Error;
 
@@ -263,7 +276,12 @@ 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

@@ -1,5 +1,3 @@
-using System.Collections.Immutable;
-
 namespace Railway.Tests.Errors;
 
 public class Serialization
@@ -8,35 +6,64 @@ public class Serialization
     public void WhenSerializingManyErrors()
     {
         // Given
-        Error many_errors = new ManyErrors(new Error[]{
+        Error many_errors = new ManyErrors(
-            new ExpectedError("err1", "msg1"){
+        [
-                ExtensionData = ImmutableDictionary<string, string>.Empty
+            Error.New("err1", "msg1", new KeyValuePair<string, string>[]
-                    .Add("ext", "ext_value"),
+            {
-            },
+                new("ext", "ext_value"),
-            new ExceptionalError(new Exception("msg2")),
+            }),
-        });
+            Error.New(new Exception("msg2")),
+        ]);
         // When
         var result = JsonSerializer.Serialize(many_errors);
         // Then
         Assert.Equal(
-            expected: "[{\"$$err\":0,\"Type\":\"err1\",\"Message\":\"msg1\",\"ExtensionData\":{\"ext\":\"ext_value\"}},{\"$$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 = "[{\"$$err\":0,\"Type\":\"err1\",\"Message\":\"msg1\",\"ExtensionData\":{\"ext1\":\"ext_value1\",\"ext2\":\"ext_value2\"}},{\"$$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[]{
+            expected: Error.Many(
-                new ExpectedError("err1", "msg1"),
+                Error.New("err1", "msg1"),
-                new ExceptionalError(new Exception("msg2")),
+                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(

Raliway.Tests/Results/GeneralUsage.cs

@@ -128,4 +128,45 @@ public class GeneralUsage
         // Then
         Assert.Equal("satisfied", result);
     }
+
+    [Fact]
+    public void RecoverResultFromFailureState()
+    {
+        // Given
+        Result<string> failed = new NotImplementedException();
+        // When
+        var result = failed.TryRecover(err => 
+        {
+            Assert.IsType<NotImplementedException>(err.ToException());
+
+            if (err.Type == "System.NotImplementedException")
+                return "recovered";
+
+            Assert.Fail();
+            return "";
+        });
+        // Then
+        Assert.True(result.IsSuccess);
+        Assert.Equal("recovered", result.Value);
+    }
+
+    [Fact]
+    public void WhenCanNotRecoverResultFromFailureState()
+    {
+        // Given
+        var error = Error.New("test");
+        Result<string> failed = new NotImplementedException();
+        // When
+        var result = failed.TryRecover(err =>
+        {
+            if (err.Type == "System.NotImplementedException")
+                return error;
+            
+            Assert.Fail();
+            return "";
+        });
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(error, result.Error);
+    }
 }