[clang-format] Add a new style for the clang-format source code (#69814)

Author: owenca

clang/include/clang/Format/Format.h

@@ -4861,6 +4861,8 @@ FormatStyle getGNUStyle();
 /// https://docs.microsoft.com/en-us/visualstudio/ide/editorconfig-code-style-settings-reference?view=vs-2017
 FormatStyle getMicrosoftStyle(FormatStyle::LanguageKind Language);
 
+FormatStyle getClangFormatStyle();
+
 /// Returns style indicating formatting should be not applied at all.
 FormatStyle getNoStyle();
 

clang/lib/Format/Format.cpp

@@ -834,8 +834,8 @@ template <> struct MappingTraits<FormatStyle> {
 
     StringRef BasedOnStyle;
     if (IO.outputting()) {
-      StringRef Styles[] = {"LLVM",   "Google", "Chromium", "Mozilla",
-                            "WebKit", "GNU",    "Microsoft"};
+      StringRef Styles[] = {"LLVM",   "Google", "Chromium",  "Mozilla",
+                            "WebKit", "GNU",    "Microsoft", "clang-format"};
       for (StringRef StyleName : Styles) {
         FormatStyle PredefinedStyle;
         if (getPredefinedStyle(StyleName, Style.Language, &PredefinedStyle) &&
@@ -1915,6 +1915,16 @@ FormatStyle getMicrosoftStyle(FormatStyle::LanguageKind Language) {
   return Style;
 }
 
+FormatStyle getClangFormatStyle() {
+  FormatStyle Style = getLLVMStyle();
+  Style.InsertBraces = true;
+  Style.InsertNewlineAtEOF = true;
+  Style.LineEnding = FormatStyle::LE_LF;
+  Style.RemoveBracesLLVM = true;
+  Style.RemoveParentheses = FormatStyle::RPS_ReturnStatement;
+  return Style;
+}
+
 FormatStyle getNoStyle() {
   FormatStyle NoStyle = getLLVMStyle();
   NoStyle.DisableFormat = true;
@@ -1939,6 +1949,8 @@ bool getPredefinedStyle(StringRef Name, FormatStyle::LanguageKind Language,
     *Style = getGNUStyle();
   else if (Name.equals_insensitive("microsoft"))
     *Style = getMicrosoftStyle(Language);
+  else if (Name.equals_insensitive("clang-format"))
+    *Style = getClangFormatStyle();
   else if (Name.equals_insensitive("none"))
     *Style = getNoStyle();
   else if (Name.equals_insensitive("inheritparentconfig"))

clang/unittests/Format/ConfigParseTest.cpp

@@ -63,6 +63,13 @@ TEST(ConfigParseTest, GetsPredefinedStyleByName) {
   EXPECT_TRUE(getPredefinedStyle("gnU", FormatStyle::LK_Cpp, &Styles[2]));
   EXPECT_ALL_STYLES_EQUAL(Styles);
 
+  Styles[0] = getClangFormatStyle();
+  EXPECT_TRUE(
+      getPredefinedStyle("clang-format", FormatStyle::LK_Cpp, &Styles[1]));
+  EXPECT_TRUE(
+      getPredefinedStyle("Clang-format", FormatStyle::LK_Cpp, &Styles[2]));
+  EXPECT_ALL_STYLES_EQUAL(Styles);
+
   EXPECT_FALSE(getPredefinedStyle("qwerty", FormatStyle::LK_Cpp, &Styles[0]));
 }