[clang] 00ca105 - [clang-format] Fixing erroneous trailing comma (#205631)

[via cfe-commits]

Author: Barry Revzin
Date: 2026-06-26T20:56:08+02:00
New Revision: 00ca10569f366f59a6a6f52fdd2f0ce8b9128a01

URL: https://github.com/llvm/llvm-project/commit/00ca10569f366f59a6a6f52fdd2f0ce8b9128a01
DIFF: https://github.com/llvm/llvm-project/commit/00ca10569f366f59a6a6f52fdd2f0ce8b9128a01.diff

LOG: [clang-format] Fixing erroneous trailing comma (#205631)

Fixes #205571

---------

Co-authored-by: Barry Revzin <brevzin at jumptrading.com>
Co-authored-by: Björn Schäpers <bjoern at hazardy.de>

Added: 
    

Modified: 
    clang/lib/Format/Format.cpp
    clang/lib/Format/FormatToken.h
    clang/unittests/Format/FormatTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index 51a976783b589..ecfe5d2ce60d0 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -2824,12 +2824,12 @@ class EnumTrailingCommaEditor : public TokenAnalyzer {
   void editEnumTrailingComma(SmallVectorImpl<AnnotatedLine *> &Lines,
                              tooling::Replacements &Result) {
     bool InEnumBraces = false;
-    const FormatToken *BeforeRBrace = nullptr;
+    FormatToken *BeforeRBrace = nullptr;
     const auto &SourceMgr = Env.getSourceManager();
     for (auto *Line : Lines) {
       if (!Line->Children.empty())
         editEnumTrailingComma(Line->Children, Result);
-      for (const auto *Token = Line->First; Token && !Token->Finalized;
+      for (auto *Token = Line->First; Token && !Token->Finalized;
            Token = Token->Next) {
         if (Token->isNot(TT_EnumRBrace)) {
           if (Token->is(TT_EnumLBrace))
@@ -2839,8 +2839,10 @@ class EnumTrailingCommaEditor : public TokenAnalyzer {
           continue;
         }
         InEnumBraces = false;
-        if (!BeforeRBrace) // Empty braces or Line not affected.
+        if (!BeforeRBrace || BeforeRBrace->HasEnumTrailingCommaHandled) {
+          // Empty braces, or Line not affected, or already handled.
           continue;
+        }
         if (BeforeRBrace->is(tok::comma)) {
           if (Style.EnumTrailingComma == FormatStyle::ETC_Remove)
             replaceToken(*BeforeRBrace, BeforeRBrace->Next, SourceMgr, Result);
@@ -2848,6 +2850,7 @@ class EnumTrailingCommaEditor : public TokenAnalyzer {
           cantFail(Result.add(tooling::Replacement(
               SourceMgr, BeforeRBrace->Tok.getEndLoc(), 0, ",")));
         }
+        BeforeRBrace->HasEnumTrailingCommaHandled = true;
         BeforeRBrace = nullptr;
       }
     }

diff  --git a/clang/lib/Format/FormatToken.h b/clang/lib/Format/FormatToken.h
index ed9ce435ea765..0eeb95950ea2b 100644
--- a/clang/lib/Format/FormatToken.h
+++ b/clang/lib/Format/FormatToken.h
@@ -331,9 +331,9 @@ struct FormatToken {
         EndsBinaryExpression(false), PartOfMultiVariableDeclStmt(false),
         ContinuesLineCommentSection(false), Finalized(false),
         ClosesRequiresClause(false), EndsCppAttributeGroup(false),
-        BlockKind(BK_Unknown), Decision(FD_Unformatted),
-        PackingKind(PPK_Inconclusive), TypeIsFinalized(false),
-        Type(TT_Unknown) {}
+        HasEnumTrailingCommaHandled(false), BlockKind(BK_Unknown),
+        Decision(FD_Unformatted), PackingKind(PPK_Inconclusive),
+        TypeIsFinalized(false), Type(TT_Unknown) {}
 
   /// The \c Token.
   Token Tok;
@@ -409,6 +409,9 @@ struct FormatToken {
   /// \c true if this token ends a group of C++ attributes.
   unsigned EndsCppAttributeGroup : 1;
 
+  /// \c true if a comma has been inserted or removed after the token.
+  unsigned HasEnumTrailingCommaHandled : 1;
+
 private:
   /// Contains the kind of block if this token is a brace.
   unsigned BlockKind : 2;

diff  --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index c42cc147cf21e..78ddb27e61e95 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -25210,6 +25210,19 @@ TEST_F(FormatTest, EnumTrailingComma) {
                "  MY_ENUM = 0U\n"
                "};",
                Style);
+
+  // Issue https://github.com/llvm/llvm-project/issues/205571
+  verifyFormat("#ifdef FOO\n"
+               "#else\n"
+               "#endif\n"
+               "enum {\n"
+               "  E = 1,\n"
+               "};",
+               "#ifdef FOO\n"
+               "#else\n"
+               "#endif\n"
+               "enum { E = 1 };",
+               Style);
 }
 
 TEST_F(FormatTest, BreakAfterAttributes) {