Suppress pedantic diagnostic for a file not ending in EOL

clang-tools-extra/clangd/Preamble.cpp

@@ -628,7 +628,6 @@ buildPreamble(PathRef FileName, CompilerInvocation CI,
     switch (Info.getID()) {
     case diag::warn_no_newline_eof:
     case diag::warn_cxx98_compat_no_newline_eof:
-    case diag::ext_no_newline_eof:
       // If the preamble doesn't span the whole file, drop the no newline at
       // eof warnings.
       return Bounds.Size != ContentsBuffer->getBufferSize()

clang/docs/ReleaseNotes.rst

@@ -128,7 +128,10 @@ C2y Feature Support
   also removes UB with code like ``(void)(void)1;``.
 - Implemented `WG14 N3411 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3411.pdf>`_
   which allows a source file to not end with a newline character. This is still
-  reported as a conforming extension in earlier language modes.
+  reported as a conforming extension in earlier language modes. Note,
+  ``-pedantic`` will no longer diagnose this in either C or C++ modes as an
+  extension. This feature was adopted as applying to obsolete versions of C in
+  WG14 and as a defect report in WG21 (CWG787).
 - Implemented `WG14 N3353 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3353.htm>_`
   which adds the new ``0o`` and ``0O`` ocal literal prefixes and deprecates
   octal literals other than ``0`` which do not start with the new prefix. This

clang/include/clang/Basic/DiagnosticLexKinds.td

@@ -52,8 +52,6 @@ def ext_multi_line_line_comment : Extension<"multi-line // comment">,
 def ext_line_comment : Extension<
   "// comments are not allowed in this language">,
   InGroup<Comment>;
-def ext_no_newline_eof : Extension<"no newline at end of file">,
-  InGroup<NewlineEOF>;
 def warn_no_newline_eof : Warning<"no newline at end of file">,
   InGroup<NewlineEOF>, DefaultIgnore;
 

clang/lib/Lex/Lexer.cpp

@@ -3194,18 +3194,12 @@ bool Lexer::LexEndOfFile(Token &Result, const char *CurPtr) {
     SourceLocation EndLoc = getSourceLocation(BufferEnd);
     unsigned DiagID = diag::warn_no_newline_eof;
 
-    if (LangOpts.CPlusPlus11) {
-      // C++11 [lex.phases] 2.2 p2
-      // Prefer the C++98 pedantic compatibility warning over the generic,
-      // non-extension, user-requested "missing newline at EOF" warning.
-      if (!Diags.isIgnored(diag::warn_cxx98_compat_no_newline_eof, EndLoc))
-        DiagID = diag::warn_cxx98_compat_no_newline_eof;
-    } else {
-      // This is conforming in C2y, but is an extension in earlier language
-      // modes.
-      if (!LangOpts.C2y)
-        DiagID = diag::ext_no_newline_eof;
-    }
+    // C++11 [lex.phases] 2.2 p2
+    // Prefer the C++98 pedantic compatibility warning over the generic,
+    // non-extension, user-requested "missing newline at EOF" warning.
+    if (LangOpts.CPlusPlus11 &&
+        !Diags.isIgnored(diag::warn_cxx98_compat_no_newline_eof, EndLoc))
+      DiagID = diag::warn_cxx98_compat_no_newline_eof;
 
     Diag(BufferEnd, DiagID) << FixItHint::CreateInsertion(EndLoc, "\n");
   }

clang/test/C/C2y/n3411.c

@@ -1,7 +1,8 @@
 // RUN: %clang_cc1 -verify=good -std=c2y -Wall -pedantic %s
 // RUN: %clang_cc1 -verify -Wnewline-eof -std=c2y -Wall -pedantic %s
-// RUN: %clang_cc1 -verify -std=c23 -Wall -pedantic %s
+// RUN: %clang_cc1 -verify=good -std=c23 -Wall -pedantic %s
 // RUN: %clang_cc1 -verify=good -std=c23 %s
+// RUN: %clang_cc1 -verify -Wnewline-eof -std=c23 %s
 
 /* WG14 N3411: Yes
  * Slay Some Earthly Demons XII

clang/test/Lexer/newline-eof.c

@@ -1,11 +1,16 @@
-// RUN: %clang_cc1 -fsyntax-only -Wnewline-eof -verify %s
-// RUN: %clang_cc1 -fsyntax-only -pedantic -verify %s
-// RUN: %clang_cc1 -fsyntax-only -x c++ -std=c++03 -pedantic -verify %s
-// RUN: %clang_cc1 -fsyntax-only -Wnewline-eof %s 2>&1 | FileCheck %s
+// Allowing a file to end without a newline was adopted as a Defect Report in
+// WG21 (CWG787) and in WG14 (added to the list of changes which apply to
+// earlier revisions of C in C2y). So it should not issue a pedantic diagnostic
+// in any language mode.
 
-// In C++11 mode, this is allowed, so don't warn in pedantic mode.
+// RUN: %clang_cc1 -fsyntax-only -Wnewline-eof -verify %s
+// RUN: %clang_cc1 -fsyntax-only -pedantic -verify=good %s
+// RUN: %clang_cc1 -fsyntax-only -std=c89 -pedantic -Wno-comment -verify=good %s
+// RUN: %clang_cc1 -fsyntax-only -x c++ -std=c++03 -pedantic -verify=good %s
 // RUN: %clang_cc1 -fsyntax-only -x c++ -std=c++11 -Wnewline-eof -verify %s
 // RUN: %clang_cc1 -fsyntax-only -x c++ -std=c++11 -Werror -pedantic %s
+// RUN: %clang_cc1 -fsyntax-only -Wnewline-eof %s 2>&1 | FileCheck %s
+// good-no-diagnostics
 
 // Make sure the diagnostic shows up properly at the end of the last line.
 // CHECK: newline-eof.c:[[@LINE+3]]:67