Change Prettify to not prefix identifiers starting with numbers

This lets us handle prefixing and prettification separately, which notably is important if we add prefixes after prettification.
We want to prefix the final name, not the intermediate name in this case.

Author: Exanite

sources/SilkTouch/SilkTouch/Mods/PrettifyNames.cs

@@ -508,6 +508,7 @@ NamePrettifier namePrettifier
         result = nameAffixer.RemoveAffixes(result, container, name, null);
         result = namePrettifier.Prettify(result, allowAllCaps);
         result = nameAffixer.ApplyAffixes(result, container, name, null);
+        result = NameUtils.PrefixIfStartsWithNumber(result);
 
         return result;
     }
@@ -1505,7 +1506,7 @@ public void Trim(NameTrimmerContext context)
                 foreach (var (original, (primary, secondary)) in context.Names)
                 {
                     var secondaries = secondary;
-                    var newPrimary = affixer.ApplyAffixes(primary, null, original, secondaries);
+                    var newPrimary = affixer.ApplyAffixes(primary, null, original, secondaries); // TODO: Prefix names starting with numbers
                     context.Names[original] = new CandidateNames(newPrimary, secondaries);
                 }
 

sources/SilkTouch/SilkTouch/Naming/NamePrettifier.cs

@@ -31,11 +31,6 @@ public class NamePrettifier(int longAcronymThreshold)
     /// <exception cref="InvalidOperationException">Thrown when the input or output is an empty identifier.</exception>
     public string Prettify(string identifier, bool allowAllCaps = false)
     {
-        if (identifier.Length == 0)
-        {
-            throw new InvalidOperationException("Cannot prettify an empty identifier");
-        }
-
         var words = NameSplitter.BreakIntoWords(identifier);
 
         // Add "X" to separate out numbers
@@ -50,15 +45,6 @@ public string Prettify(string identifier, bool allowAllCaps = false)
             }
         }
 
-        // Add "X" if first word is a number
-        if (words.Count > 0)
-        {
-            if (NameUtils.GetCharType(words[0][0]) is CharType.Number)
-            {
-                words.Insert(0, "X");
-            }
-        }
-
         // Pretend there is an underscore between each word
         // This is used as a heuristic for determining whether we can treat short, all uppercase words as acronyms
         //
@@ -179,17 +165,11 @@ public string Prettify(string identifier, bool allowAllCaps = false)
             }
         }
 
-        var result = string.Join("", words);
-        if (result.Length == 0)
-        {
-            throw new InvalidOperationException(
-                $"Prettification for '{identifier}' led to an empty identifier"
-            );
-        }
+        var result = string.Join(null, words);
 
         // Disallow all capitals
         var resultSpan = result.AsSpan();
-        if (!allowAllCaps && IsAllCaps(result))
+        if (result.Length > 0 && !allowAllCaps && IsAllCaps(result))
         {
             Span<char> caps = stackalloc char[resultSpan.Length - 1];
             resultSpan[1..].ToLower(caps, CultureInfo.InvariantCulture);

sources/SilkTouch/SilkTouch/Naming/NameUtils.cs

@@ -38,6 +38,19 @@ public static partial class NameUtils
         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_"
     );
 
+    /// <summary>
+    /// Prefixes the given identifier with the specified prefix if it starts with a number.
+    /// </summary>
+    public static string PrefixIfStartsWithNumber(string identifier, string prefix = "X")
+    {
+        if (identifier.Length > 0 && char.IsDigit(identifier[0]))
+        {
+            return $"X{identifier}";
+        }
+
+        return identifier;
+    }
+
     /// <summary>
     /// Gets the char type for the specified character according
     /// to the categorization defined by <see cref="CharType"/>.

tests/SilkTouch/SilkTouch/Naming/NamePrettifierTests.cs

@@ -71,16 +71,19 @@ public string AcronymsWithNumbers2(string input, int longAcronymThreshold = 0) =
     public string ConsecutiveAcronyms(string input, int longAcronymThreshold = 0) =>
         new NamePrettifier(longAcronymThreshold).Prettify(input);
 
+    /// <summary>
+    /// C# identifiers cannot start with numbers, but <see cref="NamePrettifier.Prettify"/> no longer handles this
+    /// in favor of calling <see cref="NameUtils.PrefixIfStartsWithNumber"/> separately.
+    /// </summary>
     [Theory]
-    // C# identifiers cannot start with numbers
-    [TestCase("123", ExpectedResult = "X123")]
-    [TestCase("123Hello", ExpectedResult = "X123Hello")]
+    [TestCase("123", ExpectedResult = "123")]
+    [TestCase("123Hello", ExpectedResult = "123Hello")]
     public string StartsWithNumber(string input, int longAcronymThreshold = 0) =>
         new NamePrettifier(longAcronymThreshold).Prettify(input);
 
     [Theory]
     // Add x between numbers to maintain separation
-    [TestCase("123_123_123", ExpectedResult = "X123x123x123")]
+    [TestCase("123_123_123", ExpectedResult = "123x123x123")]
     [TestCase("Hello123_123_123", ExpectedResult = "Hello123x123x123")]
     [TestCase("Hello123X123X123", ExpectedResult = "Hello123x123x123")]
     public string ConsecutiveNumbers(string input, int longAcronymThreshold = 0) =>
@@ -172,4 +175,18 @@ public void Lowercase_AfterNumber_IsPartOf_NewWord()
             Assert.That(nameTransformer.Prettify("MONO16f"), Is.EqualTo("Mono16F"));
         }
     }
+
+    [Test]
+    public void EmptyInput_IsAllowed()
+    {
+        var nameTransformer = new NamePrettifier(4);
+        nameTransformer.Prettify("");
+    }
+
+    [Test]
+    public void EmptyOutput_IsAllowed()
+    {
+        var nameTransformer = new NamePrettifier(4);
+        nameTransformer.Prettify("_");
+    }
 }

tests/SilkTouch/SilkTouch/Naming/NameTrimmerTests.cs

@@ -77,7 +77,7 @@ public void RegressionFragmentShaderColorModMaskATI()
         );
         var expected = new Dictionary<string, string>
         {
-            { "GL_2X_BIT_ATI", "X2XBitAti" },
+            { "GL_2X_BIT_ATI", "2XBitAti" },
             { "GL_COMP_BIT_ATI", "CompBitAti" },
             { "GL_NEGATE_BIT_ATI", "NegateBitAti" },
             { "GL_BIAS_BIT_ATI", "BiasBitAti" },