From 19a636faa82e72deb856e2361054bfe1e4c1b60d Mon Sep 17 00:00:00 2001
From: Manfred Brands <manfred-brands@users.noreply.github.com>
Date: Fri, 21 Nov 2025 09:16:36 +0800
Subject: [PATCH] CA1708: Ignore 'extension' blocks for naming check.

---
 .../IdentifiersShouldDifferByMoreThanCase.cs  |  3 +-
 .../Extensions/INamedTypeSymbolExtensions.cs  |  4 +++
 .../Compiler/Extensions/ISymbolExtensions.cs  |  5 ++++
 ...ntifiersShouldDifferByMoreThanCaseTests.cs | 29 +++++++++++++++++++
 4 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Microsoft.CodeAnalysis.NetAnalyzers/Microsoft.CodeQuality.Analyzers/ApiDesignGuidelines/IdentifiersShouldDifferByMoreThanCase.cs b/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Microsoft.CodeAnalysis.NetAnalyzers/Microsoft.CodeQuality.Analyzers/ApiDesignGuidelines/IdentifiersShouldDifferByMoreThanCase.cs
index 887585aab992..d905b372fc19 100644
--- a/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Microsoft.CodeAnalysis.NetAnalyzers/Microsoft.CodeQuality.Analyzers/ApiDesignGuidelines/IdentifiersShouldDifferByMoreThanCase.cs
+++ b/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Microsoft.CodeAnalysis.NetAnalyzers/Microsoft.CodeQuality.Analyzers/ApiDesignGuidelines/IdentifiersShouldDifferByMoreThanCase.cs
@@ -142,11 +142,12 @@ private static void CheckTypeMembers(IEnumerable<ISymbol> members, Action<Diagno
             using var membersByName = PooledDictionary<string, PooledHashSet<ISymbol>>.GetInstance(StringComparer.OrdinalIgnoreCase);
             foreach (var member in members)
             {
-                // Ignore constructors, indexers, operators and destructors for name check
+                // Ignore constructors, indexers, operators, destructors and extension blocks for name check
                 if (member.IsConstructor() ||
                     member.IsDestructor() ||
                     member.IsIndexer() ||
                     member.IsUserDefinedOperator() ||
+                    member.IsExtension() ||
                     overloadsToSkip.Contains(member))
                 {
                     continue;
diff --git a/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Utilities/Compiler/Extensions/INamedTypeSymbolExtensions.cs b/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Utilities/Compiler/Extensions/INamedTypeSymbolExtensions.cs
index 9c395554d9a6..0559da8a4418 100644
--- a/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Utilities/Compiler/Extensions/INamedTypeSymbolExtensions.cs
+++ b/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Utilities/Compiler/Extensions/INamedTypeSymbolExtensions.cs
@@ -17,8 +17,12 @@ internal static class INamedTypeSymbolExtensions
 
         private static readonly Func<INamedTypeSymbol, bool> s_isFileLocal = LightupHelpers.CreateSymbolPropertyAccessor<INamedTypeSymbol, bool>(typeof(INamedTypeSymbol), nameof(IsFileLocal), fallbackResult: false);
 
+        private static readonly Func<INamedTypeSymbol, bool> s_isExtension = LightupHelpers.CreateSymbolPropertyAccessor<INamedTypeSymbol, bool>(typeof(INamedTypeSymbol), nameof(IsExtension), fallbackResult: false);
+
         public static bool IsFileLocal(this INamedTypeSymbol symbol) => s_isFileLocal(symbol);
 
+        public static bool IsExtension(this INamedTypeSymbol symbol) => s_isExtension(symbol);
+
         public static IEnumerable<INamedTypeSymbol> GetBaseTypesAndThis(this INamedTypeSymbol type)
         {
             INamedTypeSymbol current = type;
diff --git a/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Utilities/Compiler/Extensions/ISymbolExtensions.cs b/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Utilities/Compiler/Extensions/ISymbolExtensions.cs
index 03b9c0e21630..e3a352b3718e 100644
--- a/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Utilities/Compiler/Extensions/ISymbolExtensions.cs
+++ b/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Utilities/Compiler/Extensions/ISymbolExtensions.cs
@@ -161,6 +161,11 @@ public static bool IsConversionOperator([NotNullWhen(returnValue: true)] this IS
             return symbol is IMethodSymbol { MethodKind: MethodKind.Conversion };
         }
 
+        public static bool IsExtension([NotNullWhen(returnValue: true)] this ISymbol? symbol)
+        {
+            return symbol is INamedTypeSymbol namedTypeSymbol && namedTypeSymbol.IsExtension();
+        }
+
         public static ImmutableArray<IParameterSymbol> GetParameters(this ISymbol? symbol)
         {
             return symbol switch
diff --git a/src/Microsoft.CodeAnalysis.NetAnalyzers/tests/Microsoft.CodeAnalysis.NetAnalyzers.UnitTests/Microsoft.CodeQuality.Analyzers/ApiDesignGuidelines/IdentifiersShouldDifferByMoreThanCaseTests.cs b/src/Microsoft.CodeAnalysis.NetAnalyzers/tests/Microsoft.CodeAnalysis.NetAnalyzers.UnitTests/Microsoft.CodeQuality.Analyzers/ApiDesignGuidelines/IdentifiersShouldDifferByMoreThanCaseTests.cs
index 5da69d2d9eda..ecc347e95df9 100644
--- a/src/Microsoft.CodeAnalysis.NetAnalyzers/tests/Microsoft.CodeAnalysis.NetAnalyzers.UnitTests/Microsoft.CodeQuality.Analyzers/ApiDesignGuidelines/IdentifiersShouldDifferByMoreThanCaseTests.cs
+++ b/src/Microsoft.CodeAnalysis.NetAnalyzers/tests/Microsoft.CodeAnalysis.NetAnalyzers.UnitTests/Microsoft.CodeQuality.Analyzers/ApiDesignGuidelines/IdentifiersShouldDifferByMoreThanCaseTests.cs
@@ -419,6 +419,35 @@ public partial class D
             GetCA1708CSharpResultAt(30, 30, Parameter, "N.D.SomeDelegate"));
         }
 
+        [Fact]
+        public async Task TestMultipleExtensionBlocks()
+        {
+            string code = @"
+public static class StringExtensions
+{
+    private const string ExtensionString = ""Extension"";
+
+    // Static class extensions
+    extension(string)
+    {
+        public static string CreateExtension() => ExtensionString;
+    }
+
+    // Instance extensions
+    extension(string s)
+    {
+        public bool IsExtensionString() => s == ExtensionString;
+    }
+}
+";
+
+            await new VerifyCS.Test
+            {
+                TestCode = code,
+                LanguageVersion = CodeAnalysis.CSharp.LanguageVersion.CSharp14,
+            }.RunAsync();
+        }
+
         #endregion
 
         #region Helper Methods