Inital structure, basic abstractions and tests, CI workflow

.gitattributes

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+# automatically normalize line endings
+* text=auto eol=crlf
+

.github/workflows/CI.yml

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+name: CI
+
+env:
+  SOLUTION: RailwayResult.sln
+  DOTNET_NOLOGO: true                     # Disable the .NET logo
+  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true # Disable the .NET first time experience
+  DOTNET_CLI_TELEMETRY_OPTOUT: true       # Disable sending .NET CLI telemetry
+
+on:
+  workflow_dispatch:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+jobs:
+  build:
+    name: Build & Test
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: 8.0.x
+
+      - name: Restore
+        run: dotnet restore ${{ env.SOLUTION }}
+
+      - name: Build
+        run: dotnet build ${{ env.SOLUTION }} -c Release --no-restore
+
+      - name: Test
+        run: dotnet test ${{env.SOLUTION }} -c Release --no-build --verbosity minimal

Directory.Build.props

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+<Project>
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
+    <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
+  </PropertyGroup>
+</Project>
+

Directory.Packages.props

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+<Project>
+  <PropertyGroup>
+    <CentralPackageVersionOverrideEnabled>false</CentralPackageVersionOverrideEnabled>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageVersion Include="coverlet.collector" Version="6.0.0" />
+    <PackageVersion Include="FluentAssertions" Version="6.12.0" />
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+    <PackageVersion Include="xunit" Version="2.5.3" />
+    <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.3" />
+  </ItemGroup>
+</Project>

RailwayResult.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{D27FC398-A542-46F4-A335-C6D1A7C73F36}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "RailwayResult", "src\RailwayResult\RailwayResult.csproj", "{C290883E-72EC-433E-BB3F-83B58381F9FF}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "tests", "tests", "{9AF71DD6-A91C-429D-9E17-91DB64571176}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "RailwayResult.Tests", "tests\RailwayResult.Tests\RailwayResult.Tests.csproj", "{BF48CBB9-7B8A-4376-9094-D71B093E0660}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{A8011620-9912-4139-B2A2-72C334F2DB82}"
+	ProjectSection(SolutionItems) = preProject
+		.editorconfig = .editorconfig
+		Directory.Build.props = Directory.Build.props
+		Directory.Packages.props = Directory.Packages.props
+	EndProjectSection
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{C290883E-72EC-433E-BB3F-83B58381F9FF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{C290883E-72EC-433E-BB3F-83B58381F9FF}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{C290883E-72EC-433E-BB3F-83B58381F9FF}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{C290883E-72EC-433E-BB3F-83B58381F9FF}.Release|Any CPU.Build.0 = Release|Any CPU
+		{BF48CBB9-7B8A-4376-9094-D71B093E0660}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{BF48CBB9-7B8A-4376-9094-D71B093E0660}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{BF48CBB9-7B8A-4376-9094-D71B093E0660}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{BF48CBB9-7B8A-4376-9094-D71B093E0660}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(NestedProjects) = preSolution
+		{C290883E-72EC-433E-BB3F-83B58381F9FF} = {D27FC398-A542-46F4-A335-C6D1A7C73F36}
+		{BF48CBB9-7B8A-4376-9094-D71B093E0660} = {9AF71DD6-A91C-429D-9E17-91DB64571176}
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {54E35DCC-CE9C-4B2C-A050-D7E86E862BDD}
+	EndGlobalSection
+EndGlobal

src/RailwayResult/Error.cs

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+namespace RailwayResult;
+
+public abstract record Error<TSelf> : ErrorBase where TSelf : Error<TSelf>, new()
+{
+	public static TSelf New(string message, string key = "")
+	{
+		return new TSelf()
+		{
+			Key = key,
+			Message = message
+		};
+	}
+}

src/RailwayResult/ErrorBase.cs

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+namespace RailwayResult;
+
+public abstract record ErrorBase
+{
+	public string Key { get; protected init; } = null!;
+	public string Message { get; protected init; } = null!;
+}

src/RailwayResult/Exceptions/AccesingFailedResulsException.cs

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+namespace RailwayResult.Exceptions;
+
+public sealed class AccessingValueOfFailureResultException : InvalidOperationException
+{
+	public AccessingValueOfFailureResultException() : base("Value of failure result cannot be accessed.") { }
+}

src/RailwayResult/Exceptions/AccessingErrorOfSuccessResultException.cs

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+namespace RailwayResult.Exceptions;
+
+public sealed class AccessingErrorOfSuccessResultException : InvalidOperationException
+{
+	public AccessingErrorOfSuccessResultException() : base("Error of success result cannot be accessed.") { }
+}

src/RailwayResult/RailwayResult.csproj

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+<Project Sdk="Microsoft.NET.Sdk" />

src/RailwayResult/Result.Generic.cs

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+using RailwayResult.Exceptions;
+
+namespace RailwayResult;
+
+public sealed class Result<TValue>
+{
+	public bool IsSuccess { get; }
+	public bool IsFailure => !IsSuccess;
+
+	private readonly TValue? _value;
+	public TValue Value => IsSuccess ? _value! : throw new AccessingValueOfFailureResultException();
+
+	private readonly ErrorBase? _error = null;
+	public ErrorBase Error => IsFailure ? _error! : throw new AccessingErrorOfSuccessResultException();
+
+	private Result(ErrorBase error)
+	{
+		IsSuccess = false;
+		_error = error;
+		_value = default;
+	}
+
+	private Result(TValue? value)
+	{
+		IsSuccess = true;
+		_error = null;
+		_value = value;
+	}
+
+	public TOut Match<TOut>(Func<TValue, TOut> successMap, Func<ErrorBase, TOut> failureMap)
+	{
+		return IsSuccess ? successMap(_value!) : failureMap(_error!);
+	}
+
+	public static Result<TValue> Success(TValue value) => new(value);
+
+	public static implicit operator Result<TValue>(TValue? value) => new(value);
+	public static implicit operator Result<TValue>(ErrorBase error) => new(error);
+}

src/RailwayResult/Result.cs

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+using RailwayResult.Exceptions;
+
+namespace RailwayResult;
+
+public sealed class Result
+{
+	public bool IsSuccess { get; }
+	public bool IsFailure => !IsSuccess;
+
+	private readonly ErrorBase? _error = null;
+	public ErrorBase Error => IsFailure ? _error! : throw new AccessingErrorOfSuccessResultException();
+
+	public Result(ErrorBase error)
+	{
+		IsSuccess = false;
+		_error = error;
+	}
+
+	private Result()
+	{
+		IsSuccess = true;
+		_error = null;
+	}
+
+	public static readonly Result Success = new();
+
+	public static implicit operator Result(ErrorBase error) => new(error);
+}

tests/RailwayResult.Tests/GlobalUsings.cs

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+global using FluentAssertions;
+
+global using RailwayResult;
+global using RailwayResult.Exceptions;
+
+global using RailwayResults.Tests.Mocks;
+
+global using Xunit;

tests/RailwayResult.Tests/Mocks/GenericError.cs

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+using RailwayResult;
+
+namespace RailwayResults.Tests.Mocks;
+
+public sealed record GenericError : Error<GenericError>;

tests/RailwayResult.Tests/RailwayResult.Tests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" />
+    <PackageReference Include="FluentAssertions" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="xunit" />
+    <PackageReference Include="xunit.runner.visualstudio" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\RailwayResult\RailwayResult.csproj" />
+  </ItemGroup>
+
+</Project>

tests/RailwayResult.Tests/ResultTests.cs

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+namespace RailwayResult.Tests;
+
+public sealed class ResultTests
+{
+	[Fact]
+	public void AccessingValueOfFailureResult_Should_ResultInException()
+	{
+		//arrange
+		Result<string> failedResult = GenericError.New("Error");
+
+		//act
+		var accessor = () => failedResult.Value;
+
+		//assert
+		accessor.Should().ThrowExactly<AccessingValueOfFailureResultException>();
+	}
+
+	[Fact]
+	public void AccessingErrorOfSuccessResult_Should_ResultInException()
+	{
+		//arrange
+		Result result = Result.Success;
+
+		//act
+		var accessor = () => result.Error;
+
+		//assert
+		accessor.Should().ThrowExactly<AccessingErrorOfSuccessResultException>();
+	}
+
+	[Fact]
+	public void AccessingErrorOfGenericSuccessResult_Should_ResultInException()
+	{
+		//arrange
+		Result<string> result = "Success";
+
+		//act
+		var accessor = () => result.Error;
+
+		//assert
+		accessor.Should().ThrowExactly<AccessingErrorOfSuccessResultException>();
+	}
+}