[Unity CodeDom] Editor-time code generator. Generates constant-declaration-only classes for Tags, Layers, Sorting layers and Input axes. Good for type-safety. #Unity #Unity3d #CodeDom

CodeGenerator_Window.cs

using Microsoft.CSharp;
using System.CodeDom;
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using UnityEditor;
using UnityEditorInternal;
using UnityEngine;

public class CodeGenerator_Window : EditorWindow
{
    private string axesPath = @"Scripts/Auto/Axes.cs";
    private string tagsPath = @"Scripts/Auto/Tags.cs";
    private string sortingLayersPath = @"Scripts/Auto/SortingLayers.cs";
    private string layersPath = @"Scripts/Auto/Layers.cs";

    [MenuItem("Window/Code Generator")]
    private static void CallCreateWindow()
    {
        // Get existing open window or if none, make a new one:
        CodeGenerator_Window window = (CodeGenerator_Window)EditorWindow.GetWindow(typeof(CodeGenerator_Window));
        window.autoRepaintOnSceneChange = true;
        window.title = "Code Generator";
        window.Show();
    }

    private void OnInspectorUpdate()
    {
        this.Repaint();
    }

    private void OnGUI()
    {
        DrawGenerationGui("Input", ref this.axesPath, GetAllAxisNames);
        EditorGUILayout.Separator();
        DrawGenerationGui("Tags", ref this.tagsPath, GetAllTags);
        EditorGUILayout.Separator();
        DrawGenerationGui("Sorting layers", ref this.sortingLayersPath, GetAllSortingLayers);
        EditorGUILayout.Separator();
        DrawGenerationGui("Layers", ref this.layersPath, GetAllLayers);
    }

    private static void DrawGenerationGui(string title, ref string path, System.Func<IEnumerable<string>> namesProvider)
    {
        EditorGUILayout.BeginVertical(EditorStyles.inspectorFullWidthMargins);
        EditorGUILayout.LabelField(title, EditorStyles.boldLabel);

        EditorGUILayout.PrefixLabel(@"Path: /Assets/... + ");
        path = EditorGUILayout.TextField(path, EditorStyles.textField);

        EditorGUILayout.BeginHorizontal();
        GUILayout.FlexibleSpace();
        if (GUILayout.Button("Generate", EditorStyles.miniButton))
        {
            try
            {
                GenerateAndForceImport(path, namesProvider);
                System.GC.Collect();
            }
            catch (System.Exception ex)
            {
                Debug.LogException(ex);
            }
        }
        GUILayout.FlexibleSpace();
        EditorGUILayout.EndHorizontal();

        EditorGUILayout.EndVertical();
    }

    #region code generation
    private static void GenerateAndForceImport(string path, System.Func<IEnumerable<string>> namesProvider)
    {
        var fullPath = Path.Combine(Application.dataPath, path);

        var names = namesProvider();
        if (names.Any())
        {
            GenerateNamesCodeFile(fullPath, names);

            AssetDatabase.ImportAsset(fullPath, ImportAssetOptions.ForceUpdate);
            AssetDatabase.Refresh();
        }
        else
            EditorUtility.DisplayDialog("No data", "No names found.", "Close");
    }

    private static void GenerateNamesCodeFile(string fullPath, IEnumerable<string> names)
    {
        var name = Path.GetFileNameWithoutExtension(fullPath);
        var constants = names.ToDictionary(s => ConvertToValidIdentifier(s), s => s);

        var code = CreateStringConstantsClass(name, constants);

        Directory.CreateDirectory(Path.GetDirectoryName(fullPath));
        using (var stream = new StreamWriter(fullPath, append: false))
        {
            var tw = new IndentedTextWriter(stream);
            var codeProvider = new CSharpCodeProvider();
            codeProvider.GenerateCodeFromCompileUnit(code, tw, new CodeGeneratorOptions());
        }
    }

    private static CodeCompileUnit CreateStringConstantsClass(
        string name,
        IDictionary<string, string> constants)
    {
        var compileUnit = new CodeCompileUnit();
        var @namespace = new CodeNamespace();

        var @class = new CodeTypeDeclaration(name);

        ImitateStaticClass(@class);

        foreach (var pair in constants)
        {
            var @const = new CodeMemberField(
                typeof(string),
                pair.Key);
            @const.Attributes &= ~MemberAttributes.AccessMask;
            @const.Attributes &= ~MemberAttributes.ScopeMask;
            @const.Attributes |= MemberAttributes.Public;
            @const.Attributes |= MemberAttributes.Const;

            @const.InitExpression = new CodePrimitiveExpression(pair.Value);
            @class.Members.Add(@const);
        }

        @namespace.Types.Add(@class);
        compileUnit.Namespaces.Add(@namespace);

        return compileUnit;
    }

    /// <summary>
    /// Marks class as sealed and adds private constructor to it.
    /// </summary>
    /// <remarks>
    /// It's not possible to create static class using CodeDom.
    /// Creating abstract sealed class instead leads to compilation error.
    /// This method can be used instead to make pseudo-static class.
    /// </remarks>
    private static void ImitateStaticClass(CodeTypeDeclaration type)
    {
        @type.TypeAttributes |= TypeAttributes.Sealed;

        @type.Members.Add(new CodeConstructor
        {
            Attributes = MemberAttributes.Private | MemberAttributes.Final
        });
    }

    private static string ConvertToValidIdentifier(string name)
    {
        var sb = new StringBuilder(name.Length + 1);

        if (!char.IsLetter(name[0]))
            sb.Append('_');

        var makeUpper = false;
        foreach (var ch in name)
        {
            if (char.IsLetterOrDigit(ch))
            {
                sb.Append(makeUpper
                    ? char.ToUpperInvariant(ch)
                    : ch);
                makeUpper = false;
            }
            else if (char.IsWhiteSpace(ch))
            {
                makeUpper = true;
            }
            else
            {
                sb.Append('_');
            }
        }

        return sb.ToString();
    }
    #endregion

    #region names providers
    private static IEnumerable<string> GetAllAxisNames()
    {
        var result = new StringCollection();

        var serializedObject = new SerializedObject(AssetDatabase.LoadAllAssetsAtPath("ProjectSettings/InputManager.asset")[0]);
        var axesProperty = serializedObject.FindProperty("m_Axes");

        axesProperty.Next(true);
        axesProperty.Next(true);

        while (axesProperty.Next(false))
        {
            SerializedProperty axis = axesProperty.Copy();
            axis.Next(true);
            result.Add(axis.stringValue);
        }

        return result.Cast<string>().Distinct();
    }

    private static IEnumerable<string> GetAllTags()
    {
        return new ReadOnlyCollection<string>(InternalEditorUtility.tags);
    }

    private static IEnumerable<string> GetAllSortingLayers()
    {
        var internalEditorUtilityType = typeof(InternalEditorUtility);
        var sortingLayersProperty = internalEditorUtilityType.GetProperty("sortingLayerNames", BindingFlags.Static | BindingFlags.NonPublic);
        var sortingLayers = (string[])sortingLayersProperty.GetValue(null, new object[0]);

        return new ReadOnlyCollection<string>(sortingLayers);
    }

    private static IEnumerable<string> GetAllLayers()
    {
        return new ReadOnlyCollection<string>(InternalEditorUtility.layers);
    }
    #endregion
}

Result.cs

// ------------------------------------------------------------------------------
//  <autogenerated>
//      This code was generated by a tool.
//      Mono Runtime Version: 2.0.50727.1433
// 
//      Changes to this file may cause incorrect behavior and will be lost if 
//      the code is regenerated.
//  </autogenerated>
// ------------------------------------------------------------------------------



public sealed class Axes {
    
    public const string Horizontal = "Horizontal";
    
    public const string Vertical = "Vertical";
    
    public const string Fire1 = "Fire1";
    
    public const string Fire2 = "Fire2";
    
    public const string Fire3 = "Fire3";
    
    public const string Jump = "Jump";
    
    public const string MouseX = "Mouse X";
    
    public const string MouseY = "Mouse Y";
    
    public const string MouseScrollWheel = "Mouse ScrollWheel";
    
    public const string Submit = "Submit";
    
    public const string Cancel = "Cancel";
    
    private Axes() {
    }
}

There's also my post:
Russian or
Auto-translated into English
The post itself is not too helpful (it's faster to understand the code directly than to read a ton of words about it). But the criticism of my approach in comments is interesting and has valid points.

I added your comment as a quote to the Readme.
I also added UPM support to the GitHub repo, so it can be used directly with https://github.com/mob-sakai/UpmGitExtension.