[format] foo.<name>.h should be the main-header for foo.<name>.cc

[hokein]

Summary

This fixes a regression introduced in https://reviews.llvm.org/D88640.

[sammccall]

Thank you!

clang/lib/Tooling/Inclusions/HeaderIncludes.cpp

243

nit: comment is internally inconsistent here, which makes it a bit hard to follow.

• either use bullets for both lists, or for neither
• either use placeholders like 'foo' or like '<name>', but not both
• list the most important/obvious examples at the top for both cases

[hokein]

address comment.

clang/include/clang/Tooling/Inclusions/HeaderIncludes.h

public:
   int getSortIncludePriority(StringRef IncludeName, bool CheckMainHeader) const;
 
 private:
   bool isMainHeader(StringRef IncludeName) const;
 
   const IncludeStyle Style;
   bool IsMainFile;
   std::string FileName;
-  // This refers to a substring in FileName.
-  StringRef FileStem;
   SmallVector<llvm::Regex, 4> CategoryRegexs;
 };
 
 /// Generates replacements for inserting or deleting #include directives in a
 /// file.
 class HeaderIncludes {
 public:
   HeaderIncludes(llvm::StringRef FileName, llvm::StringRef Code,

clang/lib/Tooling/Inclusions/HeaderIncludes.cpp

StringRef matchingStem(llvm::StringRef Path) {
   return Name.substr(0, Name.find('.', 1));
 }
 
 } // anonymous namespace
 
 IncludeCategoryManager::IncludeCategoryManager(const IncludeStyle &Style,
                                                StringRef FileName)
     : Style(Style), FileName(FileName) {
-  FileStem = matchingStem(FileName);
   for (const auto &Category : Style.IncludeCategories)
     CategoryRegexs.emplace_back(Category.Regex, llvm::Regex::IgnoreCase);
   IsMainFile = FileName.endswith(".c") || FileName.endswith(".cc") ||
                FileName.endswith(".cpp") || FileName.endswith(".c++") ||
                FileName.endswith(".cxx") || FileName.endswith(".m") ||
                FileName.endswith(".mm");
   if (!Style.IncludeIsMainSourceRegex.empty()) {
     llvm::Regex MainFileRegex(Style.IncludeIsMainSourceRegex);
int IncludeCategoryManager::getSortIncludePriority(StringRef IncludeName,
   if (CheckMainHeader && IsMainFile && Ret > 0 && isMainHeader(IncludeName))
     Ret = 0;
   return Ret;
 }
 bool IncludeCategoryManager::isMainHeader(StringRef IncludeName) const {
   if (!IncludeName.startswith("\""))
     return false;
 
+  IncludeName =
+      IncludeName.drop_front(1).drop_back(1); // remove the surrounding "" or <>
   // Not matchingStem: implementation files may have compound extensions but
   // headers may not.
-  StringRef HeaderStem =
-      llvm::sys::path::stem(IncludeName.drop_front(1).drop_back(
-          1) /* remove the surrounding "" or <> */);
-  if (FileStem.startswith(HeaderStem) ||
-      FileStem.startswith_lower(HeaderStem)) {
+  StringRef HeaderStem = llvm::sys::path::stem(IncludeName);
+  StringRef FileStem = llvm::sys::path::stem(FileName); // foo.cu for foo.cu.cc
+  StringRef MatchingFileStem = matchingStem(FileName);  // foo for foo.cu.cc
+  // main-header examples:
+  //  1) foo.h => foo.cc
+  //  2) foo.h => foo.cu.cc
+  //  3) foo.proto.h => foo.proto.cc
+  //
+  // non-main-header examples:
+  //  1) foo.h => bar.cc
+  //  2) foo.proto.h => foo.cc
+  StringRef Matching;
+  if (MatchingFileStem.startswith_lower(HeaderStem))
+    Matching = MatchingFileStem; // example 1), 2)
+  else if (FileStem.equals_lower(HeaderStem))
+    Matching = FileStem; // example 3)
+  if (!Matching.empty()) {
     llvm::Regex MainIncludeRegex(HeaderStem.str() + Style.IncludeIsMainRegex,
                                  llvm::Regex::IgnoreCase);
-    if (MainIncludeRegex.match(FileStem))
+    if (MainIncludeRegex.match(Matching))
       return true;
   }
   return false;
 }
 
 HeaderIncludes::HeaderIncludes(StringRef FileName, StringRef Code,
                                const IncludeStyle &Style)
     : FileName(FileName), Code(Code), FirstIncludeOffset(-1),

clang/unittests/Format/SortIncludesTest.cpp

std::string Code = "#include <a>\n"
                      "#include <b>\n"
                      "#include <c>\n"
                      "#include <d>\n"
                      "#include <e>\n"
                      "#include <f>\n";
   EXPECT_TRUE(sortIncludes(FmtStyle, Code, GetCodeRange(Code), "a.cc").empty());
 }
 
-TEST_F(SortIncludesTest, NoMainFileHeader) {
+TEST_F(SortIncludesTest, MainFileHeader) {
   std::string Code = "#include <string>\n"
                      "\n"
                      "#include \"a/extra_action.proto.h\"\n";
   FmtStyle = getGoogleStyle(FormatStyle::LK_Cpp);
   EXPECT_TRUE(
       sortIncludes(FmtStyle, Code, GetCodeRange(Code), "a/extra_action.cc")
           .empty());
+
+  EXPECT_EQ("#include \"foo.bar.h\"\n"
+            "\n"
+            "#include \"a.h\"\n",
+            sort("#include \"a.h\"\n"
+                 "#include \"foo.bar.h\"\n",
+                 "foo.bar.cc"));
 }
 
 TEST_F(SortIncludesTest, SortedIncludesInMultipleBlocksAreMerged) {
   Style.IncludeBlocks = tooling::IncludeStyle::IBS_Merge;
   EXPECT_EQ("#include \"a.h\"\n"
             "#include \"b.h\"\n"
             "#include \"c.h\"\n",
             sort("#include \"a.h\"\n"