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Khamraj Rohit
2024-08-26 16:44:09 -04:00
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MIT License
Copyright (c) 2024 Khamraj Rohit
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

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Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio Version 17
VisualStudioVersion = 17.11.35219.272
MinimumVisualStudioVersion = 10.0.40219.1
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MaybeError", "MaybeError\MaybeError.csproj", "{542F56CD-34E6-4B95-A75D-DFBC8CCC0E65}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MaybeErrorTests", "MaybeErrorTests\MaybeErrorTests.csproj", "{17467BE9-78C3-4E03-B829-FD7AA2DFB116}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|Any CPU = Debug|Any CPU
Release|Any CPU = Release|Any CPU
EndGlobalSection
GlobalSection(ProjectConfigurationPlatforms) = postSolution
{542F56CD-34E6-4B95-A75D-DFBC8CCC0E65}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{542F56CD-34E6-4B95-A75D-DFBC8CCC0E65}.Debug|Any CPU.Build.0 = Debug|Any CPU
{542F56CD-34E6-4B95-A75D-DFBC8CCC0E65}.Release|Any CPU.ActiveCfg = Release|Any CPU
{542F56CD-34E6-4B95-A75D-DFBC8CCC0E65}.Release|Any CPU.Build.0 = Release|Any CPU
{17467BE9-78C3-4E03-B829-FD7AA2DFB116}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{17467BE9-78C3-4E03-B829-FD7AA2DFB116}.Debug|Any CPU.Build.0 = Debug|Any CPU
{17467BE9-78C3-4E03-B829-FD7AA2DFB116}.Release|Any CPU.ActiveCfg = Release|Any CPU
{17467BE9-78C3-4E03-B829-FD7AA2DFB116}.Release|Any CPU.Build.0 = Release|Any CPU
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE
EndGlobalSection
GlobalSection(ExtensibilityGlobals) = postSolution
SolutionGuid = {94322BD7-955B-4456-B4B3-E46BEA356AA5}
EndGlobalSection
EndGlobal

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using System.Diagnostics.CodeAnalysis;
namespace MaybeError;
public interface IMaybe<T, E> where T: class where E : Error
{
[MemberNotNullWhen(true, nameof(Error))]
bool HasError { get; }
bool HasValue { get; }
E? Error { get; }
T Value { get; }
public T ValueOrDefault(T defaultValue)
{
if (HasError)
return defaultValue;
return Value;
}
public T? ValueOrDefault()
{
if (HasError)
return default;
return Value;
}
public R As<R>(Func<T, R> predicate)
{
return predicate(Value);
}
public R? AsOrDefault<R>(Func<T, R> predicate)
{
if (HasError)
return default;
return predicate(Value);
}
public R AsOrDefault<R>(Func<T, R> predicate, R defaultValue)
{
if (HasError)
return defaultValue;
return predicate(Value);
}
}
public readonly struct Maybe<T, E> : IMaybe<T, E> where T : class where E: Error
{
[MemberNotNullWhen(true, nameof(Error))]
public readonly bool HasError { get; }
public readonly bool HasValue { get; }
public readonly E? Error { get; }
public readonly T Value => HasError ? throw Error.GetException() : _value!;
private readonly T? _value;
public Maybe()
{
_value = default;
}
public Maybe(T value)
{
_value = value;
HasValue = true;
}
public Maybe(E e)
{
Error = e;
HasError = true;
_value = default;
}
public static implicit operator Maybe<T, E>(T value)
{
return new Maybe<T, E>(value);
}
public static implicit operator Maybe<T, E>(E e)
{
return new Maybe<T, E>(e);
}
public static implicit operator T(Maybe<T, E> value)
{
if (value.HasError)
throw value.Error.GetException();
return value.Value;
}
}
public readonly struct Maybe<T> : IMaybe<T, Error> where T : class
{
[MemberNotNullWhen(true, nameof(Error))]
public readonly bool HasError { get; }
public readonly bool HasValue { get; }
public readonly Error? Error { get; }
public readonly T Value => HasError ? throw Error.GetException() : _value!;
private readonly T? _value;
public Maybe()
{
_value = default;
}
public Maybe(T value)
{
_value = value;
HasValue = true;
}
public Maybe(Exception e)
{
Error = new ExceptionError(e);
HasError = true;
_value = default;
}
public Maybe(Error e)
{
Error = e;
HasError = true;
_value = default;
}
public static implicit operator Maybe<T>(T value)
{
return new Maybe<T>(value);
}
public static implicit operator Maybe<T>(Exception e)
{
return new Maybe<T>(e);
}
public static implicit operator Maybe<T>(Error e)
{
return new Maybe<T>(e);
}
public static implicit operator T(Maybe<T> value)
{
if (value.HasError)
throw value.Error.GetException();
return value.Value;
}
}
public class Error(string message, string? details = null, string? debugDetails = null)
{
public readonly string Message = message;
public readonly string? Details = details;
public readonly string? DebugDetails = debugDetails;
public virtual Exception GetException()
{
return new Exception(Message);
}
public override string ToString()
{
return $"{Message}\n{Details}\n{DebugDetails}";
}
public static implicit operator string(Error e)
{
return e.ToString();
}
}
public class ExceptionError : ExceptionError<Exception>
{
public ExceptionError(string message, Exception exception) : base(message, exception)
{
}
public ExceptionError(Exception exception) : base(exception)
{
}
}
public class ExceptionError<T> : Error where T : Exception
{
public T Exception { get; set; }
public ExceptionError(string message, T exception) : base(message, exception.Message, exception.StackTrace)
{
Exception = exception;
}
public ExceptionError(T exception) : base(exception.Message, debugDetails: exception.StackTrace)
{
Exception = exception;
}
public override T GetException()
{
return Exception;
}
public override string ToString()
{
return $"{Message}\n{Exception}";
}
}

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<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFramework>net8.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
</PropertyGroup>
</Project>

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#nullable enable
namespace MaybeError;
public static class MaybeExtensions
{
public static T ValueOrDefault<T, E>(this IValueMaybe<T, E> maybe, T defaultValue) where T : struct where E : Error
{
if (maybe.HasError)
return defaultValue;
return maybe.Value;
}
public static T? ValueOrDefault<T, E>(this IValueMaybe<T, E> maybe) where T : struct where E : Error
{
if (maybe.HasError)
return default;
return maybe.Value;
}
public static R As<R, T, E>(this IValueMaybe<T, E> maybe, Func<T, R> predicate) where T : struct where E : Error
{
return predicate(maybe.Value);
}
public static R? AsOrDefault<R, T, E>(this IValueMaybe<T, E> maybe, Func<T, R> predicate) where T : struct where E : Error
{
if (maybe.HasError)
return default;
return predicate(maybe.Value);
}
public static R AsOrDefault<R, T, E>(this IValueMaybe<T, E> maybe, Func<T, R> predicate, R defaultValue) where T : struct where E : Error
{
if (maybe.HasError)
return defaultValue;
return predicate(maybe.Value);
}
public static T ValueOrDefault<T, E>(this IMaybe<T, E> maybe, T defaultValue) where T : class where E : Error
{
if (maybe.HasError)
return defaultValue;
return maybe.Value;
}
public static T? ValueOrDefault<T, E>(this IMaybe<T, E> maybe) where T : class where E : Error
{
if (maybe.HasError)
return default;
return maybe.Value;
}
public static R As<R, T, E>(this IMaybe<T, E> maybe, Func<T, R> predicate) where T : class where E : Error
{
return predicate(maybe.Value);
}
public static R? AsOrDefault<R, T, E>(this IMaybe<T, E> maybe, Func<T, R> predicate) where T : class where E : Error
{
if (maybe.HasError)
return default;
return predicate(maybe.Value);
}
public static R AsOrDefault<R, T, E>(this IMaybe<T, E> maybe, Func<T, R> predicate, R defaultValue) where T : class where E : Error
{
if (maybe.HasError)
return defaultValue;
return predicate(maybe.Value);
}
}

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using System.Diagnostics.CodeAnalysis;
namespace MaybeError;
public interface IValueMaybe<T, E> where T : struct where E : Error
{
[MemberNotNullWhen(true, nameof(Error))]
bool HasError { get; }
bool HasValue => !HasError;
E? Error { get; }
T Value { get; }
}
public readonly struct ValueMaybe<T, E> : IValueMaybe<T, E> where T : struct where E : Error
{
[MemberNotNullWhen(true, nameof(Error))]
public readonly bool HasError { get; }
public readonly bool HasValue => !HasError;
public readonly E? Error { get; }
public readonly T Value => HasError ? throw Error.GetException() : _value;
private readonly T _value;
public ValueMaybe()
{
_value = default;
}
public ValueMaybe(T value)
{
_value = value;
HasError = false;
}
public ValueMaybe(E e)
{
Error = e;
HasError = true;
_value = default;
}
public static implicit operator ValueMaybe<T, E>(T value)
{
return new ValueMaybe<T, E>(value);
}
public static implicit operator ValueMaybe<T, E>(E e)
{
return new ValueMaybe<T, E>(e);
}
public static implicit operator T(ValueMaybe<T, E> value)
{
if (value.HasError)
throw value.Error.GetException();
return value.Value;
}
}
public readonly struct ValueMaybe<T> : IValueMaybe<T, Error> where T : struct
{
[MemberNotNullWhen(true, nameof(Error))]
public readonly bool HasError { get; }
public readonly bool HasValue => !HasError;
public readonly Error? Error { get; }
public readonly T Value => HasError ? throw Error.GetException() : _value;
private readonly T _value;
public ValueMaybe()
{
_value = default;
}
public ValueMaybe(T value)
{
_value = value;
HasError = false;
}
public ValueMaybe(Exception e)
{
Error = new ExceptionError(e);
HasError = true;
_value = default;
}
public ValueMaybe(Error e)
{
Error = e;
HasError = true;
_value = default;
}
public static implicit operator ValueMaybe<T>(T value)
{
return new ValueMaybe<T>(value);
}
public static implicit operator ValueMaybe<T>(Exception e)
{
return new ValueMaybe<T>(e);
}
public static implicit operator ValueMaybe<T>(Error e)
{
return new ValueMaybe<T>(e);
}
public static implicit operator T(ValueMaybe<T> value)
{
if (value.HasError)
throw value.Error.GetException();
return value.Value;
}
}

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<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFramework>net8.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
<IsPackable>false</IsPackable>
<IsTestProject>true</IsTestProject>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="coverlet.collector" Version="6.0.0" />
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
<PackageReference Include="NUnit" Version="3.14.0" />
<PackageReference Include="NUnit.Analyzers" Version="3.9.0" />
<PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
</ItemGroup>
<ItemGroup>
<ProjectReference Include="..\MaybeError\MaybeError.csproj" />
</ItemGroup>
<ItemGroup>
<Using Include="NUnit.Framework" />
</ItemGroup>
</Project>

108
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using MaybeError;
namespace MaybeErrorTests;
public class MaybeTests
{
[Test]
public void HasValue()
{
Maybe<string> value = "Test";
if (value.HasValue)
Assert.That(value.Value, Is.EqualTo("Test"));
else
Assert.Fail();
Assert.That(value.Error, Is.Null);
}
[Test]
public void HasError()
{
Maybe<string> value = new InvalidOperationException();
if (value.HasError)
Assert.That(value.Error, Is.Not.Null);
else
Assert.Fail();
Assert.Throws<InvalidOperationException>(() => value.Value.ToLower());
}
[Test]
public void ImplicitValue()
{
Maybe<string> value = "Test";
Assert.That(value == "Test", Is.True);
}
[Test]
public void ImplicitError()
{
Maybe<string> value = new InvalidOperationException();
Assert.Throws<InvalidOperationException>(() => value.Value.ToString());
}
[Test]
public void ExplicitError()
{
Maybe<string, ExceptionError> value = new ExceptionError(new InvalidOperationException());
Assert.Throws<InvalidOperationException>(() => value.Value.ToString());
}
[Test]
public void Error()
{
Maybe<string> value = new Error("Test Error");
Assert.Throws<Exception>(() => value.Value.ToLower());
Assert.That(value.HasError);
Assert.That(value.Error?.Message, Is.EqualTo("Test Error"));
}
[Test]
public void ValueOrDefault()
{
Maybe<string> value = "Test";
Assert.That(value.ValueOrDefault(), Is.EqualTo("Test"));
value = new InvalidOperationException();
Assert.That(value.ValueOrDefault(), Is.Null);
}
[Test]
public void ValueOrDefaultWithDefault()
{
Maybe<string> value = "Test";
Assert.That(value.ValueOrDefault("Err"), Is.EqualTo("Test"));
value = new InvalidOperationException();
Assert.That(value.ValueOrDefault("Err"), Is.EqualTo("Err"));
}
[Test]
public void As()
{
Maybe<string> value = "Test";
Assert.That(value.As(v => v.Length), Is.EqualTo(4));
value = new InvalidOperationException();
Assert.Throws<InvalidOperationException>(() => value.As(v => v.Length));
}
[Test]
public void AsOrDefault()
{
Maybe<string> value = "Test";
Assert.That(value.AsOrDefault(v => v.Length), Is.EqualTo(4));
value = new InvalidOperationException();
Assert.That(value.AsOrDefault(v => v.Length), Is.EqualTo(0));
}
[Test]
public void AsOrDefaultWithValue()
{
Maybe<string> value = "Test";
Assert.That(value.AsOrDefault(v => v.Length, -4), Is.EqualTo(4));
value = new InvalidOperationException();
Assert.That(value.AsOrDefault(v => v.Length, -4), Is.EqualTo(-4));
}
}

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using MaybeError;
namespace MaybeErrorTests;
public class ValueMaybeTests
{
[Test]
public void HasValue()
{
ValueMaybe<int> value = 1;
if(value.HasValue)
Assert.That(value.Value, Is.EqualTo(1));
else
Assert.Fail();
Assert.That(value.Error, Is.Null);
}
[Test]
public void HasError()
{
ValueMaybe<int> value = new InvalidOperationException();
if (value.HasError)
Assert.That(value.Error, Is.Not.Null);
else
Assert.Fail();
Assert.Throws<InvalidOperationException>(() => value.Value.ToString());
}
[Test]
public void ImplicitValue()
{
ValueMaybe<int> value = 1;
Assert.That(value == 1, Is.True);
}
[Test]
public void ImplicitError()
{
ValueMaybe<int> value = new InvalidOperationException();
Assert.Throws<InvalidOperationException>(() => value.Value.ToString());
}
[Test]
public void ExplicitError()
{
ValueMaybe<int, ExceptionError> value = new ExceptionError(new InvalidOperationException());
Assert.Throws<InvalidOperationException>(() => value.Value.ToString());
}
[Test]
public void Error()
{
ValueMaybe<int> value = new Error("Test Error");
Assert.Throws<Exception>(() => value.Value.ToString());
Assert.That(value.HasError);
Assert.That(value.Error?.Message, Is.EqualTo("Test Error"));
}
[Test]
public void ValueOrDefault()
{
ValueMaybe<int> value = 1;
Assert.That(value.ValueOrDefault(), Is.EqualTo(1));
value = new InvalidOperationException();
Assert.That(value.ValueOrDefault(), Is.Null);
}
[Test]
public void ValueOrDefaultWithDefault()
{
ValueMaybe<int> value = 1;
Assert.That(value.ValueOrDefault(3), Is.EqualTo(1));
value = new InvalidOperationException();
Assert.That(value.ValueOrDefault(3), Is.EqualTo(3));
}
[Test]
public void As()
{
ValueMaybe<int> value = 1;
Assert.That(value.As(v => v.ToString()), Is.EqualTo("1"));
value = new InvalidOperationException();
Assert.Throws<InvalidOperationException>(() => value.As(v => v.ToString()));
}
[Test]
public void AsOrDefault()
{
ValueMaybe<int> value = 1;
Assert.That(value.AsOrDefault(v => v.ToString()), Is.EqualTo("1"));
value = new InvalidOperationException();
Assert.That(value.AsOrDefault(v => v.ToString()), Is.Null);
}
[Test]
public void AsOrDefaultWithValue()
{
ValueMaybe<int> value = 1;
Assert.That(value.AsOrDefault(v => v.ToString(), "err"), Is.EqualTo("1"));
value = new InvalidOperationException();
Assert.That(value.AsOrDefault(v => v.ToString(), "err"), Is.EqualTo("err"));
}
}

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# MaybeError
A simple library to allow "error as values" functionallity in C#