[Format] Don't treat compound extension headers (foo.proto.h) as foo.cc main-file header.

We receive internal bugs about this false positives after D86597.

Differential Revision: https://reviews.llvm.org/D88640.

Author: hokein

clang/lib/Tooling/Inclusions/HeaderIncludes.cpp

@@ -233,7 +233,12 @@ int IncludeCategoryManager::getSortIncludePriority(StringRef IncludeName,
 bool IncludeCategoryManager::isMainHeader(StringRef IncludeName) const {
   if (!IncludeName.startswith("\""))
     return false;
-  StringRef HeaderStem = matchingStem(IncludeName.drop_front(1).drop_back(1));
+
+  // 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)) {
     llvm::Regex MainIncludeRegex(HeaderStem.str() + Style.IncludeIsMainRegex,

clang/unittests/Format/SortIncludesTest.cpp

@@ -151,6 +151,16 @@ TEST_F(SortIncludesTest, NoReplacementsForValidIncludes) {
   EXPECT_TRUE(sortIncludes(FmtStyle, Code, GetCodeRange(Code), "a.cc").empty());
 }
 
+TEST_F(SortIncludesTest, NoMainFileHeader) {
+  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());
+}
+
 TEST_F(SortIncludesTest, SortedIncludesInMultipleBlocksAreMerged) {
   Style.IncludeBlocks = tooling::IncludeStyle::IBS_Merge;
   EXPECT_EQ("#include \"a.h\"\n"