[clang-format] Add IndentCaseBlocks option

[capn]

Summary

The documentation for IndentCaseLabels claimed that the "Switch
statement body is always indented one level more than case labels". This
is technically false for the code block immediately following the label.
Its closing bracket aligns with the start of the label.

If the case label are not indented, it leads to a style where the
closing bracket of the block aligns with the closing bracket of the
switch statement, which can be hard to parse.

This change introduces a new option, IndentCaseBlocks, which when true
treats the block as a scope block (which it technically is).

[MyDeveloperDay]

Could you add an entry into the clang-format section of the clang release notes

clang/unittests/Format/FormatTest.cpp

1235

Could you add a test with indented case labels and indented case blocks?

[MyDeveloperDay]

clang/unittests/Format/FormatTest.cpp

1235

what happens if there are not braces {}

[capn]

Added release note update and test for both case labels and blocks being indented.

[capn]

Added case without {} to tests to ensure that still works as expected too.

[MyDeveloperDay]

This LGTM, thanks for the patch

[capn]

Thanks for the review! I don't have committer access, feel free to land at your convenience.

[capn]

Ping. Please land on my behalf.

clang/docs/ClangFormatStyleOptions.rst

**IncludeIsMainSourceRegex** (``std::string``)
   ``ClassImpl.hpp`` would not have the main include file put on top
   before any other include.
 
 **IndentCaseLabels** (``bool``)
   Indent case labels one level from the switch statement.
 
   When ``false``, use the same indentation level as for the switch
   statement. Switch statement body is always indented one level more than
-  case labels.
+  case labels (except the first block following the case label, which
+  itself indents the code - unless IndentCaseBlocks is enabled).
 
   .. code-block:: c++
 
      false:                                 true:
      switch (fool) {                vs.     switch (fool) {
      case 1:                                  case 1:
        bar();                                   bar();
        break;                                   break;
      default:                                 default:
        plop();                                  plop();
      }                                      }
 
+**IndentCaseBlocks** (``bool``)
+  Indent case label blocks one level from the case label.
+
+  When ``false``, the block following the case label uses the same
+  indentation level as for the case label, treating the case label the same
+  as an if-statement.
+  When ``true``, the block gets indented as a scope block.
+ 
+  .. code-block:: c++
+     false:                                 true:
+     switch (fool) {                vs.     switch (fool) {
+     case 1: {                              case 1:
+       bar();                                 {
+     } break;                                   bar();
+     default: {                               }
+       plop();                                break;
+     }                                      default:
+     }                                        {
+                                                plop();
+                                              }
+                                            }
+
 **IndentGotoLabels** (``bool``)
   Indent goto labels.
 
   When ``false``, goto labels are flushed left.
 
   .. code-block:: c++
 
      true:                                  false:

clang/include/clang/Format/Format.h

   std::vector<std::string> NamespaceMacros;
 
   tooling::IncludeStyle IncludeStyle;
 
   /// Indent case labels one level from the switch statement.
   ///
   /// When ``false``, use the same indentation level as for the switch
   /// statement. Switch statement body is always indented one level more than
-  /// case labels.
+  /// case labels (except the first block following the case label, which
+  /// itself indents the code - unless IndentCaseBlocks is enabled).
   /// \code
   ///    false:                                 true:
   ///    switch (fool) {                vs.     switch (fool) {
   ///    case 1:                                  case 1:
   ///      bar();                                   bar();
   ///      break;                                   break;
   ///    default:                                 default:
   ///      plop();                                  plop();
   ///    }                                      }
   /// \endcode
   bool IndentCaseLabels;
 
+  /// Indent case label blocks one level from the case label.
+  ///
+  /// When ``false``, the block following the case label uses the same
+  /// indentation level as for the case label, treating the case label the same
+  /// as an if-statement.
+  /// When ``true``, the block gets indented as a scope block.
+  /// \code
+  ///    false:                                 true:
+  ///    switch (fool) {                vs.     switch (fool) {
+  ///    case 1: {                              case 1:
+  ///      bar();                                 {
+  ///    } break;                                   bar();
+  ///    default: {                               }
+  ///      plop();                                break;
+  ///    }                                      default:
+  ///    }                                        {
+  ///                                               plop();
+  ///                                             }
+  ///                                           }
+  /// \endcode
+  bool IndentCaseBlocks;
+
   /// Indent goto labels.
   ///
   /// When ``false``, goto labels are flushed left.
   /// \code
   ///    true:                                  false:
   ///    int f() {                      vs.     int f() {
   ///      if (foo()) {                           if (foo()) {
   ///      label1:                              label1:
return AccessModifierOffset == R.AccessModifierOffset &&
            ForEachMacros == R.ForEachMacros &&
            IncludeStyle.IncludeBlocks == R.IncludeStyle.IncludeBlocks &&
            IncludeStyle.IncludeCategories == R.IncludeStyle.IncludeCategories &&
            IncludeStyle.IncludeIsMainRegex ==
                R.IncludeStyle.IncludeIsMainRegex &&
            IncludeStyle.IncludeIsMainSourceRegex ==
                R.IncludeStyle.IncludeIsMainSourceRegex &&
            IndentCaseLabels == R.IndentCaseLabels &&
+           IndentCaseBlocks == R.IndentCaseBlocks &&
            IndentGotoLabels == R.IndentGotoLabels &&
            IndentPPDirectives == R.IndentPPDirectives &&
            IndentWidth == R.IndentWidth && Language == R.Language &&
            IndentWrappedFunctionNames == R.IndentWrappedFunctionNames &&
            JavaImportGroups == R.JavaImportGroups &&
            JavaScriptQuotes == R.JavaScriptQuotes &&
            JavaScriptWrapImports == R.JavaScriptWrapImports &&
            KeepEmptyLinesAtTheStartOfBlocks ==

clang/lib/Format/Format.cpp

static void mapping(IO &IO, FormatStyle &Style) {
     IO.mapOptional("FixNamespaceComments", Style.FixNamespaceComments);
     IO.mapOptional("ForEachMacros", Style.ForEachMacros);
     IO.mapOptional("IncludeBlocks", Style.IncludeStyle.IncludeBlocks);
     IO.mapOptional("IncludeCategories", Style.IncludeStyle.IncludeCategories);
     IO.mapOptional("IncludeIsMainRegex", Style.IncludeStyle.IncludeIsMainRegex);
     IO.mapOptional("IncludeIsMainSourceRegex",
                    Style.IncludeStyle.IncludeIsMainSourceRegex);
     IO.mapOptional("IndentCaseLabels", Style.IndentCaseLabels);
+    IO.mapOptional("IndentCaseBlocks", Style.IndentCaseBlocks);
     IO.mapOptional("IndentGotoLabels", Style.IndentGotoLabels);
     IO.mapOptional("IndentPPDirectives", Style.IndentPPDirectives);
     IO.mapOptional("IndentWidth", Style.IndentWidth);
     IO.mapOptional("IndentWrappedFunctionNames",
                    Style.IndentWrappedFunctionNames);
     IO.mapOptional("JavaImportGroups", Style.JavaImportGroups);
     IO.mapOptional("JavaScriptQuotes", Style.JavaScriptQuotes);
     IO.mapOptional("JavaScriptWrapImports", Style.JavaScriptWrapImports);
FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.ForEachMacros.push_back("BOOST_FOREACH");
   LLVMStyle.IncludeStyle.IncludeCategories = {
       {"^\"(llvm|llvm-c|clang|clang-c)/", 2, 0},
       {"^(<|\"(gtest|gmock|isl|json)/)", 3, 0},
       {".*", 1, 0}};
   LLVMStyle.IncludeStyle.IncludeIsMainRegex = "(Test)?$";
   LLVMStyle.IncludeStyle.IncludeBlocks = tooling::IncludeStyle::IBS_Preserve;
   LLVMStyle.IndentCaseLabels = false;
+  LLVMStyle.IndentCaseBlocks = false;
   LLVMStyle.IndentGotoLabels = true;
   LLVMStyle.IndentPPDirectives = FormatStyle::PPDIS_None;
   LLVMStyle.IndentWrappedFunctionNames = false;
   LLVMStyle.IndentWidth = 2;
   LLVMStyle.JavaScriptQuotes = FormatStyle::JSQS_Leave;
   LLVMStyle.JavaScriptWrapImports = true;
   LLVMStyle.TabWidth = 8;
   LLVMStyle.MaxEmptyLinesToKeep = 1;

clang/lib/Format/UnwrappedLineParser.cpp

 
 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)) {
+  if (!Style.IndentCaseBlocks && CommentsBeforeNextToken.empty() &&
+      FormatTok->Tok.is(tok::l_brace)) {
     CompoundStatementIndenter Indenter(this, Line->Level,
                                        Style.BraceWrapping.AfterCaseLabel,
                                        Style.BraceWrapping.IndentBraces);
     parseBlock(/*MustBeDeclaration=*/false);
     if (FormatTok->Tok.is(tok::kw_break)) {
       if (Style.BraceWrapping.AfterControlStatement ==
           FormatStyle::BWACS_Always)
         addUnwrappedLine();

clang/unittests/Format/FormatTest.cpp

EXPECT_EQ("switch (n)\n"
                    "    return false;\n"
                    "  }\n"
                    "  default:\n"
                    "  {\n"
                    "    return true;\n"
                    "  }\n"
                    "}",
                    Style));
+  Style.IndentCaseLabels = false;
+  Style.IndentCaseBlocks = true;
+  EXPECT_EQ("switch (n)\n"
+            "{\n"
+            "case 0:\n"
+            "  {\n"
+            "    return false;\n"
+            "  }\n"
+            "default:\n"
+            "  {\n"
+            "    return true;\n"
+            "  }\n"
+            "}",
+            format("switch (n) {\n"
+                   "case 0: {\n"
+                   "  return false;\n"
+                   "}\n"
+                   "default: {\n"
+                   "  return true;\n"
+                   "}\n"
+                   "}",
+                   Style));
 }
 
 TEST_F(FormatTest, CaseRanges) {
   verifyFormat("switch (x) {\n"
                "case 'A' ... 'Z':\n"
                "case 1 ... 5:\n"
                "case a ... b:\n"
                "  break;\n"
TEST_F(FormatTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL(BreakStringLiterals);
   CHECK_PARSE_BOOL(CompactNamespaces);
   CHECK_PARSE_BOOL(ConstructorInitializerAllOnOneLineOrOnePerLine);
   CHECK_PARSE_BOOL(DeriveLineEnding);
   CHECK_PARSE_BOOL(DerivePointerAlignment);
   CHECK_PARSE_BOOL_FIELD(DerivePointerAlignment, "DerivePointerBinding");
   CHECK_PARSE_BOOL(DisableFormat);
   CHECK_PARSE_BOOL(IndentCaseLabels);
+  CHECK_PARSE_BOOL(IndentCaseBlocks);
   CHECK_PARSE_BOOL(IndentGotoLabels);
   CHECK_PARSE_BOOL(IndentWrappedFunctionNames);
   CHECK_PARSE_BOOL(KeepEmptyLinesAtTheStartOfBlocks);
   CHECK_PARSE_BOOL(ObjCSpaceAfterProperty);
   CHECK_PARSE_BOOL(ObjCSpaceBeforeProtocolList);
   CHECK_PARSE_BOOL(Cpp11BracedListStyle);
   CHECK_PARSE_BOOL(ReflowComments);
   CHECK_PARSE_BOOL(SortIncludes);