Add "enum cloning" source generator

generators/Dalamud.EnumGenerator/Dalamud.EnumGenerator.Tests/Dalamud.EnumGenerator.Tests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net9.0</TargetFramework>
+        <Nullable>enable</Nullable>
+
+        <IsPackable>false</IsPackable>
+
+        <RootNamespace>Dalamud.EnumGenerator.Tests</RootNamespace>
+
+        <ManagePackageVersionsCentrally>false</ManagePackageVersionsCentrally>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.CodeAnalysis.CSharp.SourceGenerators.Testing.XUnit" Version="1.1.1"/>
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.2"/>
+        <PackageReference Include="xunit" Version="2.4.2"/>
+        <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
+            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+            <PrivateAssets>all</PrivateAssets>
+        </PackageReference>
+    </ItemGroup>
+
+    <ItemGroup>
+        <ProjectReference Include="..\Dalamud.EnumGenerator\Dalamud.EnumGenerator.csproj"/>
+    </ItemGroup>
+
+
+</Project>

generators/Dalamud.EnumGenerator/Dalamud.EnumGenerator.Tests/EnumCloneMapTests.cs

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+using System.Collections.Immutable;
+using System.Linq;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Xunit;
+
+namespace Dalamud.EnumGenerator.Tests;
+
+public class EnumCloneMapTests
+{
+    [Fact]
+    public void ParseMappings_SimpleLines_ParsesCorrectly()
+    {
+        var text = @"# Comment line
+My.Namespace.Target = Other.Namespace.Source
+
+Another.Target = Some.Source";
+
+        var results = Dalamud.EnumGenerator.EnumCloneGenerator.ParseMappings(text);
+
+        Assert.Equal(2, results.Length);
+        Assert.Equal("My.Namespace.Target", results[0].TargetFullName);
+        Assert.Equal("Other.Namespace.Source", results[0].SourceFullName);
+        Assert.Equal("Another.Target", results[1].TargetFullName);
+    }
+
+    [Fact]
+    public void Generator_ProducesFile_WhenSourceResolved()
+    {
+        // We'll create a compilation that contains a source enum type and add an AdditionalText mapping
+        var sourceEnum = @"namespace Foo.Bar { public enum SourceEnum { A = 1, B = 2 } }";
+
+        var mapText = "GeneratedNs.TargetEnum = Foo.Bar.SourceEnum";
+
+        var generator = new EnumCloneGenerator();
+        var driver = CSharpGeneratorDriver.Create(generator)
+            .AddAdditionalTexts(ImmutableArray.Create<AdditionalText>(new Utils.TestAdditionalFile("EnumCloneMap.txt", mapText)));
+
+        var compilation = CSharpCompilation.Create("TestGen", [CSharpSyntaxTree.ParseText(sourceEnum)],
+                                                   [MetadataReference.CreateFromFile(typeof(object).Assembly.Location)]);
+
+        driver.RunGeneratorsAndUpdateCompilation(compilation, out var newCompilation, out var diagnostics);
+
+        var generated = newCompilation.SyntaxTrees.Select(t => t.FilePath).Where(p => p.EndsWith("TargetEnum.CloneEnum.g.cs")).ToArray();
+        Assert.Single(generated);
+    }
+}

generators/Dalamud.EnumGenerator/Dalamud.EnumGenerator.Tests/Utils/TestAdditionalFile.cs

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+using System.Threading;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Dalamud.EnumGenerator.Tests.Utils;
+
+public class TestAdditionalFile : AdditionalText
+{
+    private readonly SourceText text;
+
+    public TestAdditionalFile(string path, string text)
+    {
+        Path = path;
+        this.text = SourceText.From(text);
+    }
+
+    public override SourceText GetText(CancellationToken cancellationToken = new()) => this.text;
+
+    public override string Path { get; }
+}