Merge pull request #16597 from dpoeschl/NamingStylesHandleCasingBetter

Don't emit casing-related naming violations when the violating character has no casing (making the feature noisy/unusable in other cultures)

src/EditorFeatures/Test2/Diagnostics/NamingStyles/NamingStyleTests.IdentifierCreation.Compliance.vb

@@ -90,6 +90,12 @@ Namespace Microsoft.CodeAnalysis.Editor.Implementation.Diagnostics.UnitTests
             Dim namingStyle = CreateNamingStyle(wordSeparator:="_t_", capitalizationScheme:=Capitalization.PascalCase)
             TestNameCompliance(namingStyle, "Pascal_t_Case")
         End Sub
+
+        <Fact, Trait(Traits.Feature, Traits.Features.NamingStyle)>
+        Public Sub TestPascalCaseAllowsUncasedCharacters()
+            Dim namingStyle = CreateNamingStyle(wordSeparator:="_", capitalizationScheme:=Capitalization.PascalCase)
+            TestNameCompliance(namingStyle, "私の家_2nd")
+        End Sub
 #End Region
 
 #Region "camelCase"
@@ -140,6 +146,12 @@ Namespace Microsoft.CodeAnalysis.Editor.Implementation.Diagnostics.UnitTests
             Dim namingStyle = CreateNamingStyle(wordSeparator:="_t_", capitalizationScheme:=Capitalization.CamelCase)
             TestNameCompliance(namingStyle, "camel_t_Case")
         End Sub
+
+        <Fact, Trait(Traits.Feature, Traits.Features.NamingStyle)>
+        Public Sub TestCamelCaseAllowsUncasedCharacters()
+            Dim namingStyle = CreateNamingStyle(wordSeparator:="_", capitalizationScheme:=Capitalization.CamelCase)
+            TestNameCompliance(namingStyle, "私の家_2nd")
+        End Sub
 #End Region
 
 #Region "Firstupper"
@@ -190,6 +202,12 @@ Namespace Microsoft.CodeAnalysis.Editor.Implementation.Diagnostics.UnitTests
             Dim namingStyle = CreateNamingStyle(wordSeparator:="_T_", capitalizationScheme:=Capitalization.FirstUpper)
             TestNameCompliance(namingStyle, "First_T_upper")
         End Sub
+
+        <Fact, Trait(Traits.Feature, Traits.Features.NamingStyle)>
+        Public Sub TestFirstUpperAllowsUncasedCharacters()
+            Dim namingStyle = CreateNamingStyle(capitalizationScheme:=Capitalization.FirstUpper)
+            TestNameCompliance(namingStyle, "私の家")
+        End Sub
 #End Region
 
 #Region "ALLUPPER"
@@ -234,6 +252,12 @@ Namespace Microsoft.CodeAnalysis.Editor.Implementation.Diagnostics.UnitTests
             Dim namingStyle = CreateNamingStyle(wordSeparator:="_t_", capitalizationScheme:=Capitalization.AllUpper)
             TestNameCompliance(namingStyle, "ALL_t_UPPER")
         End Sub
+
+        <Fact, Trait(Traits.Feature, Traits.Features.NamingStyle)>
+        Public Sub TestAllUpperAllowsUncasedCharacters()
+            Dim namingStyle = CreateNamingStyle(capitalizationScheme:=Capitalization.AllUpper)
+            TestNameCompliance(namingStyle, "私AB23CのDE家")
+        End Sub
 #End Region
 
 #Region "alllower"
@@ -278,6 +302,12 @@ Namespace Microsoft.CodeAnalysis.Editor.Implementation.Diagnostics.UnitTests
             Dim namingStyle = CreateNamingStyle(wordSeparator:="_T_", capitalizationScheme:=Capitalization.AllLower)
             TestNameCompliance(namingStyle, "all_T_lower")
         End Sub
+
+        <Fact, Trait(Traits.Feature, Traits.Features.NamingStyle)>
+        Public Sub TestAllLowerAllowsUncasedCharacters()
+            Dim namingStyle = CreateNamingStyle(capitalizationScheme:=Capitalization.AllLower)
+            TestNameCompliance(namingStyle, "私ab23cのde家")
+        End Sub
 #End Region
     End Class
 End Namespace

src/Workspaces/Core/Portable/NamingStyles/NamingStyle.cs

@@ -136,14 +136,14 @@ private WordSpanEnumerable GetWordSpans(string name, TextSpan nameSpan)
         private static string Substring(string name, TextSpan wordSpan)
             => name.Substring(wordSpan.Start, wordSpan.Length);
 
-        private static Func<string, TextSpan, bool> s_firstCharIsLowerCase = (val, span) => char.IsLower(val[span.Start]);
-        private static Func<string, TextSpan, bool> s_firstCharIsUpperCase = (val, span) => char.IsUpper(val[span.Start]);
+        private static Func<string, TextSpan, bool> s_firstCharIsLowerCase = (val, span) => !DoesCharacterHaveCasing(val[span.Start]) || char.IsLower(val[span.Start]);
+        private static Func<string, TextSpan, bool> s_firstCharIsUpperCase = (val, span) => !DoesCharacterHaveCasing(val[span.Start]) || char.IsUpper(val[span.Start]);
 
         private static Func<string, TextSpan, bool> s_wordIsAllUpperCase = (val, span) =>
         {
             for (int i = span.Start, n = span.End; i < n; i++)
             {
-                if (!char.IsUpper(val[i]))
+                if (DoesCharacterHaveCasing(val[i]) && !char.IsUpper(val[i]))
                 {
                     return false;
                 }
@@ -156,7 +156,7 @@ private static string Substring(string name, TextSpan wordSpan)
         {
             for (int i = span.Start, n = span.End; i < n; i++)
             {
-                if (!char.IsLower(val[i]))
+                if (DoesCharacterHaveCasing(val[i]) && !char.IsLower(val[i]))
                 {
                     return false;
                 }
@@ -264,6 +264,8 @@ private bool CheckFirstUpper(string name, TextSpan nameSpan, out string reason)
                 WorkspacesResources.These_non_leading_words_must_begin_with_a_lowercase_letter_colon_0,
                 out reason);
 
+        private static bool DoesCharacterHaveCasing(char c) => char.ToLower(c) != char.ToUpper(c);
+
         private string CreateCompliantNameDirectly(string name)
         {
             var addPrefix = !name.StartsWith(Prefix);