Escape invalid identifiers for file constants

src/ThisAssembly.Constants/Model.cs

@@ -3,6 +3,8 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
+using System.Text.RegularExpressions;
+using Microsoft.CodeAnalysis.CSharp;
 
 [DebuggerDisplay("Values = {RootArea.Values.Count}")]
 record Model(Area RootArea)
@@ -17,22 +19,46 @@ record Area(string Name, string Prefix)
     public List<Area> NestedAreas { get; init; } = new();
     public List<Constant> Values { get; init; } = new();
 
+    static string EscapeIdentifier(string identifier)
+    {
+        if (string.IsNullOrWhiteSpace(identifier))
+        {
+            return "_";
+        }
+
+        var replaced = identifier
+            .Select(c => SyntaxFacts.IsIdentifierPartCharacter(c) ? c : '_')
+            .ToArray();
+
+        var result = Regex.Replace(new string(replaced), "(_)+", "_");
+
+        if (!SyntaxFacts.IsIdentifierStartCharacter(result[0]))
+        {
+            result = "_" + result;
+        }
+
+        return result;
+    }
+
     public static Area Load(List<Constant> constants, string rootArea = "Constants")
     {
         var root = new Area(rootArea, "");
 
         foreach (var constant in constants)
         {
             //  Splits: ([area].)*[name]
-            var parts = constant.Name.Split(new[] { "." }, StringSplitOptions.RemoveEmptyEntries);
+            var parts = constant.Name.Split(new[] { "." }, StringSplitOptions.RemoveEmptyEntries)
+                .Select(EscapeIdentifier)
+                .ToArray();
+
             if (parts.Length <= 1)
             {
-                root.Values.Add(new Constant(constant.Name, constant.Value, constant.Comment));
+                root.Values.Add(constant with { Name = EscapeIdentifier(constant.Name) });
             }
             else
             {
                 var area = GetArea(root, parts.Take(parts.Length - 1));
-                var value = new Constant(parts.Skip(parts.Length - 1).First(), constant.Value, constant.Comment);
+                var value = constant with { Name = parts.Skip(parts.Length - 1).First() };
 
                 area.Values.Add(value);
             }
@@ -74,4 +100,4 @@ static Area GetArea(Area area, IEnumerable<string> areaPath)
 }
 
 [DebuggerDisplay("{Name} = {Value}")]
-record Constant(string Name, string? Value, string? Comment);
+record Constant(string Name, string? Value, string? Comment);

src/ThisAssembly.Tests/Content/Docs/12. Readme (copy).txt

@@ -0,0 +1 @@
+

src/ThisAssembly.Tests/Tests.cs

@@ -35,6 +35,10 @@ public void CanUseConstants()
     public void CanUseFileConstants()
         => Assert.Equal(ThisAssembly.Constants.Content.Docs.License, Path.Combine("Content", "Docs", "License.md"));
 
+    [Fact]
+    public void CanUseFileConstantInvalidIdentifier()
+        => Assert.Equal(ThisAssembly.Constants.Content.Docs._12._Readme_copy_, Path.Combine("Content", "Docs", "12. Readme (copy).txt"));
+
     [Fact]
     public void CanUseFileConstantLinkedFile()
         => Assert.Equal(ThisAssembly.Constants.Included.Readme, Path.Combine("Included", "Readme.txt"));