[clang-format] Improve ObjC headers detection.

[jolesiak]

Summary

This patch improves detection of ObjC header files.
Right now many ObjC headers, especially short ones, are categorized as C/C++.

Way of filtering still isn't the best, as most likely it should be token-based.

[krasimir]

Thank you! I'll go ahead and commit this for you!

lib/Format/Format.cpp

llvm::Expected<FormatStyle> getStyle(StringRef StyleName, StringRef FileName,
   }
   FormatStyle Style = getLLVMStyle();
   Style.Language = getLanguageByFileName(FileName);
 
   // This is a very crude detection of whether a header contains ObjC code that
   // should be improved over time and probably be done on tokens, not one the
   // bare content of the file.
   if (Style.Language == FormatStyle::LK_Cpp && FileName.endswith(".h") &&
-      (Code.contains("\n- (") || Code.contains("\n+ (")))
+      (Code.contains("\n- (") || Code.contains("\n+ (") ||
+       Code.contains("\n@end\n") || Code.contains("\n@end ") ||
+       Code.endswith("@end")))
     Style.Language = FormatStyle::LK_ObjC;
 
   FormatStyle FallbackStyle = getNoStyle();
   if (!getPredefinedStyle(FallbackStyleName, Style.Language, &FallbackStyle))
     return make_string_error("Invalid fallback style \"" + FallbackStyleName);
 
   if (StyleName.startswith("{")) {
     // Parse YAML/JSON style from the command line.

unittests/Format/FormatTestObjC.cpp

TEST(FormatTestObjCStyle, DetectsObjCInHeaders) {
   ASSERT_TRUE((bool)Style);
   EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
 
   Style = getStyle("LLVM", "a.h", "none", "@interface\n"
                                           "+ (id)init;");
   ASSERT_TRUE((bool)Style);
   EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
 
+  Style = getStyle("LLVM", "a.h", "none", "@interface\n"
+                                          "@end\n"
+                                          "//comment");
+  ASSERT_TRUE((bool)Style);
+  EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
+
+  Style = getStyle("LLVM", "a.h", "none", "@interface\n"
+                                          "@end //comment");
+  ASSERT_TRUE((bool)Style);
+  EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
+
   // No recognizable ObjC.
   Style = getStyle("LLVM", "a.h", "none", "void f() {}");
   ASSERT_TRUE((bool)Style);
   EXPECT_EQ(FormatStyle::LK_Cpp, Style->Language);
 }
 
 TEST_F(FormatTestObjC, FormatObjCTryCatch) {
   verifyFormat("@try {\n"