[clang-format] Add new style option IndentGotoLabels

Summary:
This option determines whether goto labels are indented according to scope. Setting this option to false causes goto labels to be flushed to the left.
This is mostly copied from [[ http://lists.llvm.org/pipermail/cfe-dev/2015-September/045014.html | this patch ]] submitted by Christian Neukirchen that didn't make its way into trunk.

```
     true:                                  false:
     int f() {                      vs.     int f() {
       if (foo()) {                           if (foo()) {
       label1:                              label1:
         bar();                                 bar();
       }                                      }
     label2:                                label2:
       return 1;                              return 1;
     }                                      }
```

Reviewers: klimek, MyDeveloperDay

Reviewed By: MyDeveloperDay

Subscribers: cfe-commits

Tags: #clang, #clang-tools-extra

Patch by: tetsuo-cpp

Differential Revision: https://reviews.llvm.org/D67037

llvm-svn: 371719

clang/docs/ClangFormatStyleOptions.rst

@@ -1527,6 +1527,23 @@ the configuration (without a prefix: ``Auto``).
        plop();                                  plop();
      }                                      }
 
+**IndentGotoLabels** (``bool``)
+  Indent goto labels.
+
+  When ``false``, goto labels are flushed left.
+
+  .. code-block:: c++
+
+     true:                                  false:
+     int f() {                      vs.     int f() {
+       if (foo()) {                           if (foo()) {
+       label1:                              label1:
+         bar();                                 bar();
+       }                                      }
+     label2:                                label2:
+       return 1;                              return 1;
+     }                                      }
+
 **IndentPPDirectives** (``PPDirectiveIndentStyle``)
   The preprocessor directive indenting style to use.
 

clang/include/clang/Format/Format.h

@@ -1265,6 +1265,22 @@ struct FormatStyle {
   /// \endcode
   bool IndentCaseLabels;
 
+  /// Indent goto labels.
+  ///
+  /// When ``false``, goto labels are flushed left.
+  /// \code
+  ///    true:                                  false:
+  ///    int f() {                      vs.     int f() {
+  ///      if (foo()) {                           if (foo()) {
+  ///      label1:                              label1:
+  ///        bar();                                 bar();
+  ///      }                                      }
+  ///    label2:                                label2:
+  ///      return 1;                              return 1;
+  ///    }                                      }
+  /// \endcode
+  bool IndentGotoLabels;
+
   /// Options for indenting preprocessor directives.
   enum PPDirectiveIndentStyle {
     /// Does not indent any directives.
@@ -1990,6 +2006,7 @@ struct FormatStyle {
            IncludeStyle.IncludeBlocks == R.IncludeStyle.IncludeBlocks &&
            IncludeStyle.IncludeCategories == R.IncludeStyle.IncludeCategories &&
            IndentCaseLabels == R.IndentCaseLabels &&
+           IndentGotoLabels == R.IndentGotoLabels &&
            IndentPPDirectives == R.IndentPPDirectives &&
            IndentWidth == R.IndentWidth && Language == R.Language &&
            IndentWrappedFunctionNames == R.IndentWrappedFunctionNames &&

clang/lib/Format/Format.cpp

@@ -453,6 +453,7 @@ template <> struct MappingTraits<FormatStyle> {
     IO.mapOptional("IncludeCategories", Style.IncludeStyle.IncludeCategories);
     IO.mapOptional("IncludeIsMainRegex", Style.IncludeStyle.IncludeIsMainRegex);
     IO.mapOptional("IndentCaseLabels", Style.IndentCaseLabels);
+    IO.mapOptional("IndentGotoLabels", Style.IndentGotoLabels);
     IO.mapOptional("IndentPPDirectives", Style.IndentPPDirectives);
     IO.mapOptional("IndentWidth", Style.IndentWidth);
     IO.mapOptional("IndentWrappedFunctionNames",
@@ -725,6 +726,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.IncludeStyle.IncludeIsMainRegex = "(Test)?$";
   LLVMStyle.IncludeStyle.IncludeBlocks = tooling::IncludeStyle::IBS_Preserve;
   LLVMStyle.IndentCaseLabels = false;
+  LLVMStyle.IndentGotoLabels = true;
   LLVMStyle.IndentPPDirectives = FormatStyle::PPDIS_None;
   LLVMStyle.IndentWrappedFunctionNames = false;
   LLVMStyle.IndentWidth = 2;

clang/lib/Format/UnwrappedLineParser.cpp

@@ -1351,7 +1351,7 @@ void UnwrappedLineParser::parseStructuralElement() {
           (TokenCount == 2 && Line->Tokens.front().Tok->is(tok::comment))) {
         if (FormatTok->Tok.is(tok::colon) && !Line->MustBeDeclaration) {
           Line->Tokens.begin()->Tok->MustBreakBefore = true;
-          parseLabel();
+          parseLabel(!Style.IndentGotoLabels);
           return;
         }
         // Recognize function-like macro usages without trailing semicolon as
@@ -1970,11 +1970,13 @@ void UnwrappedLineParser::parseDoWhile() {
   parseStructuralElement();
 }
 
-void UnwrappedLineParser::parseLabel() {
+void UnwrappedLineParser::parseLabel(bool LeftAlignLabel) {
   nextToken();
   unsigned OldLineLevel = Line->Level;
   if (Line->Level > 1 || (!Line->InPPDirective && Line->Level > 0))
     --Line->Level;
+  if (LeftAlignLabel)
+    Line->Level = 0;
   if (CommentsBeforeNextToken.empty() && FormatTok->Tok.is(tok::l_brace)) {
     CompoundStatementIndenter Indenter(this, Line->Level,
                                        Style.BraceWrapping.AfterCaseLabel,

clang/lib/Format/UnwrappedLineParser.h

@@ -106,7 +106,7 @@ class UnwrappedLineParser {
   void parseTryCatch();
   void parseForOrWhileLoop();
   void parseDoWhile();
-  void parseLabel();
+  void parseLabel(bool LeftAlignLabel = false);
   void parseCaseLabel();
   void parseSwitch();
   void parseNamespace();

clang/unittests/Format/FormatTest.cpp

@@ -1408,6 +1408,30 @@ TEST_F(FormatTest, FormatsLabels) {
                "test_label:;\n"
                "  int i = 0;\n"
                "}");
+  FormatStyle Style = getLLVMStyle();
+  Style.IndentGotoLabels = false;
+  verifyFormat("void f() {\n"
+               "  some_code();\n"
+               "test_label:\n"
+               "  some_other_code();\n"
+               "  {\n"
+               "    some_more_code();\n"
+               "another_label:\n"
+               "    some_more_code();\n"
+               "  }\n"
+               "}",
+               Style);
+  verifyFormat("{\n"
+               "  some_code();\n"
+               "test_label:\n"
+               "  some_other_code();\n"
+               "}",
+               Style);
+  verifyFormat("{\n"
+               "  some_code();\n"
+               "test_label:;\n"
+               "  int i = 0;\n"
+               "}");
 }
 
 //===----------------------------------------------------------------------===//
@@ -11779,6 +11803,7 @@ TEST_F(FormatTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL_FIELD(DerivePointerAlignment, "DerivePointerBinding");
   CHECK_PARSE_BOOL(DisableFormat);
   CHECK_PARSE_BOOL(IndentCaseLabels);
+  CHECK_PARSE_BOOL(IndentGotoLabels);
   CHECK_PARSE_BOOL(IndentWrappedFunctionNames);
   CHECK_PARSE_BOOL(KeepEmptyLinesAtTheStartOfBlocks);
   CHECK_PARSE_BOOL(ObjCSpaceAfterProperty);