[clang-format] Fix BeforeHash indent of comments above PPDirective

[owenpan]

Summary

Fixes https://github.com/llvm/llvm-project/issues/56326.

clang/lib/Format/TokenAnnotator.h

enum LineType {
   LT_ImportStatement,
   LT_ObjCDecl, // An @interface, @implementation, or @protocol line.
   LT_ObjCMethodDecl,
   LT_ObjCProperty, // An @property line.
   LT_Other,
   LT_PreprocessorDirective,
   LT_VirtualFunctionDecl,
   LT_ArrayOfStructInitializer,
+  LT_CommentAbovePPDirective,
 };
 
 class AnnotatedLine {
 public:
   AnnotatedLine(const UnwrappedLine &Line)
       : First(Line.Tokens.front().Tok), Level(Line.Level),
         MatchingOpeningBlockLineIndex(Line.MatchingOpeningBlockLineIndex),
         MatchingClosingBlockLineIndex(Line.MatchingClosingBlockLineIndex),

clang/lib/Format/TokenAnnotator.cpp

for (AnnotatedLine *Line : llvm::reverse(Lines)) {
     assert(Line->First);
 
     // If the comment is currently aligned with the line immediately following
     // it, that's probably intentional and we should keep it.
     if (NextNonCommentLine && Line->isComment() &&
         NextNonCommentLine->First->NewlinesBefore <= 1 &&
         NextNonCommentLine->First->OriginalColumn ==
             Line->First->OriginalColumn) {
+      const bool PPDirectiveOrImportStmt =
+          NextNonCommentLine->Type == LT_PreprocessorDirective ||
+          NextNonCommentLine->Type == LT_ImportStatement;
+      if (PPDirectiveOrImportStmt)
+        Line->Type = LT_CommentAbovePPDirective;
       // Align comments for preprocessor lines with the # in column 0 if
       // preprocessor lines are not indented. Otherwise, align with the next
       // line.
-      Line->Level =
-          (Style.IndentPPDirectives != FormatStyle::PPDIS_BeforeHash &&
-           (NextNonCommentLine->Type == LT_PreprocessorDirective ||
-            NextNonCommentLine->Type == LT_ImportStatement))
+      Line->Level = Style.IndentPPDirectives != FormatStyle::PPDIS_BeforeHash &&
+                            PPDirectiveOrImportStmt
                         ? 0
                         : NextNonCommentLine->Level;
     } else {
       NextNonCommentLine = Line->First->isNot(tok::r_brace) ? Line : nullptr;
     }
 
     setCommentLineLevels(Line->Children);
   }
 }
 

clang/lib/Format/UnwrappedLineFormatter.cpp

public:
 
   /// Update the indent state given that \p Line is going to be formatted
   /// next.
   void nextLine(const AnnotatedLine &Line) {
     Offset = getIndentOffset(*Line.First);
     // Update the indent level cache size so that we can rely on it
     // having the right size in adjustToUnmodifiedline.
     skipLine(Line, /*UnknownIndent=*/true);
-    if (Line.InPPDirective) {
+    if (Line.InPPDirective ||
+        (Style.IndentPPDirectives == FormatStyle::PPDIS_BeforeHash &&
+         Line.Type == LT_CommentAbovePPDirective)) {
       unsigned IndentWidth =
           (Style.PPIndentWidth >= 0) ? Style.PPIndentWidth : Style.IndentWidth;
       Indent = Line.Level * IndentWidth + AdditionalIndent;
     } else {
       Indent = getIndent(Line.Level);
     }
     if (static_cast<int>(Indent) + Offset >= 0)
       Indent += Offset;

clang/unittests/Format/FormatTest.cpp

verifyFormat("#ifdef __linux__\n"
                "    int x = 0;\n"
                "}\n"
                " #define FOO foo\n"
                "#endif\n"
                "void bar() {\n"
                "    int y = 0;\n"
                "}\n",
                style);
+  verifyFormat("#if 1\n"
+               " // some comments\n"
+               " // another\n"
+               " #define foo 1\n"
+               "// not a define comment\n"
+               "void bar() {\n"
+               "    // comment\n"
+               "    int y = 0;\n"
+               "}",
+               "#if 1\n"
+               "// some comments\n"
+               "// another\n"
+               "#define foo 1\n"
+               "// not a define comment\n"
+               "void bar() {\n"
+               "  // comment\n"
+               "  int y = 0;\n"
+               "}",
+               style);
 }
 
 TEST_F(FormatTest, IndentsPPDirectiveInReducedSpace) {
   verifyFormat("#define A(BB)", getLLVMStyleWithColumns(13));
   verifyFormat("#define A( \\\n    BB)", getLLVMStyleWithColumns(12));
   verifyFormat("#define A( \\\n    A, B)", getLLVMStyleWithColumns(12));
   // FIXME: We never break before the macro name.
   verifyFormat("#define AA( \\\n    B)", getLLVMStyleWithColumns(12));