Allow underscore digit in enum members for SA1300

Author: vweijsters

StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/NamingRules/RenameToUpperCaseCodeFixProvider.cs

@@ -55,7 +55,8 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
             foreach (var diagnostic in context.Diagnostics)
             {
                 var token = root.FindToken(diagnostic.Location.SourceSpan.Start);
-                var baseName = char.ToUpper(token.ValueText[0]) + token.ValueText.Substring(1);
+                var tokenText = token.ValueText.TrimStart('_');
+                var baseName = char.ToUpper(tokenText[0]) + tokenText.Substring(1);
                 var newName = baseName;
                 var memberSyntax = RenameHelper.GetParentDeclaration(token);
 

StyleCop.Analyzers/StyleCop.Analyzers.Test/NamingRules/SA1300UnitTests.cs

@@ -971,6 +971,39 @@ public interface IInterface
             await this.VerifyCSharpFixAsync(testCode, fixedCode).ConfigureAwait(false);
         }
 
+        [Fact]
+        [WorkItem(1935, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/1935")]
+        public async Task TestUnderscoreExclusionAsync()
+        {
+            var testCode = @"public enum TestEnum
+{
+    _12clock,
+    _12Clock,
+    _tick,
+    _Tock,
+}
+";
+
+            var fixedCode = @"public enum TestEnum
+{
+    _12clock,
+    _12Clock,
+    Tick,
+    Tock,
+}
+";
+
+            DiagnosticResult[] expected =
+            {
+                this.CSharpDiagnostic().WithLocation(5, 5).WithArguments("_tick"),
+                this.CSharpDiagnostic().WithLocation(6, 5).WithArguments("_Tock"),
+            };
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, expected, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpDiagnosticAsync(fixedCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+            await this.VerifyCSharpFixAsync(testCode, fixedCode, cancellationToken: CancellationToken.None).ConfigureAwait(false);
+        }
+
         protected override IEnumerable<DiagnosticAnalyzer> GetCSharpDiagnosticAnalyzers()
         {
             yield return new SA1300ElementMustBeginWithUpperCaseLetter();

StyleCop.Analyzers/StyleCop.Analyzers/NamingRules/SA1300ElementMustBeginWithUpperCaseLetter.cs

@@ -125,7 +125,7 @@ private static void HandleEnumDeclaration(SyntaxNodeAnalysisContext context)
 
         private static void HandleEnumMemberDeclaration(SyntaxNodeAnalysisContext context)
         {
-            CheckElementNameToken(context, ((EnumMemberDeclarationSyntax)context.Node).Identifier);
+            CheckElementNameToken(context, ((EnumMemberDeclarationSyntax)context.Node).Identifier, true);
         }
 
         private static void HandleStructDeclaration(SyntaxNodeAnalysisContext context)
@@ -200,7 +200,7 @@ private static void HandlePropertyDeclaration(SyntaxNodeAnalysisContext context)
             CheckElementNameToken(context, propertyDeclaration.Identifier);
         }
 
-        private static void CheckElementNameToken(SyntaxNodeAnalysisContext context, SyntaxToken identifier)
+        private static void CheckElementNameToken(SyntaxNodeAnalysisContext context, SyntaxToken identifier, bool allowUnderscoreDigit = false)
         {
             if (identifier.IsMissing)
             {
@@ -224,6 +224,11 @@ private static void CheckElementNameToken(SyntaxNodeAnalysisContext context, Syn
                 return;
             }
 
+            if (allowUnderscoreDigit && (identifier.ValueText.Length > 1) && (identifier.ValueText[0] == '_') && char.IsDigit(identifier.ValueText[1]))
+            {
+                return;
+            }
+
             if (NamedTypeHelpers.IsContainedInNativeMethodsClass(context.Node))
             {
                 return;