[clang-format] Add SpaceInEmptyBlock option for WebKit

[owenpan]

Summary

See PR40840

[sammccall]

clang/docs/ClangFormatStyleOptions.rst

2120

may -> will?

clang/include/clang/Format/Format.h

1802

(and here)

[thakis]

https://webkit.org/code-style-guidelines/ has one instance of { } with a space and one of {} without a space, and as far as I can tell no text that says which instance is correct. Are you sure this is the right thing for webkit style?

[owenpan]

Changed "may" to "will" and updated the diff. (Should we do the same for the SpaceInEmptyParentheses option?)

[owenpan]

In D65925#1623965, @thakis wrote:

https://webkit.org/code-style-guidelines/ has one instance of { } with a space and one of {} without a space, and as far as I can tell no text that says which instance is correct. Are you sure this is the right thing for webkit style?

The one without a space is an example of "Wrong" WebKit style there.

clang/docs/ClangFormatStyleOptions.rst

* ``BAS_AlwaysBreak`` (in configuration: ``AlwaysBreak``)
 
     .. code-block:: c++
 
       someLongFunction(
           argument1, argument2);
 
 
 
-**AlignConsecutiveMacros** (``bool``)
-  If ``true``, aligns consecutive C/C++ preprocessor macros.
-
-  This will align the C/C++ preprocessor macros of consecutive lines. This
-  will result in formattings like
-
-  .. code-block:: c++
-
-    #define SHORT_NAME       42
-    #define LONGER_NAME      0x007f
-    #define EVEN_LONGER_NAME (2)
-    #define foo(x)           (x * x)
-    #define bar(y, z)        (y + z)
-
 **AlignConsecutiveAssignments** (``bool``)
   If ``true``, aligns consecutive assignments.
 
   This will align the assignment operators of consecutive lines. This
   will result in formattings like
 
   .. code-block:: c++
 
     int aaaa = 12;
     int b    = 23;
     int ccc  = 23;
 
 **AlignConsecutiveDeclarations** (``bool``)
   If ``true``, aligns consecutive declarations.
 
   This will align the declaration names of consecutive lines. This
   will result in formattings like
 
   .. code-block:: c++
 
     int         aaaa = 12;
     float       b = 23;
     std::string ccc = 23;
 
+**AlignConsecutiveMacros** (``bool``)
+  If ``true``, aligns consecutive C/C++ preprocessor macros.
+
+  This will align C/C++ preprocessor macros of consecutive lines.
+  Will result in formattings like
+
+  .. code-block:: c++
+
+    #define SHORT_NAME       42
+    #define LONGER_NAME      0x007f
+    #define EVEN_LONGER_NAME (2)
+    #define foo(x)           (x * x)
+    #define bar(y, z)        (y + z)
+
 **AlignEscapedNewlines** (``EscapedNewlineAlignmentStyle``)
   Options for aligning backslashes in escaped newlines.
 
   Possible values:
 
   * ``ENAS_DontAlign`` (in configuration: ``DontAlign``)
     Don't align escaped newlines.
 
**ForEachMacros** (``std::vector<std::string>``)
   In the .clang-format configuration file, this can be configured like:
 
   .. code-block:: yaml
 
     ForEachMacros: ['RANGES_FOR', 'FOREACH']
 
   For example: BOOST_FOREACH.
 
-**TypenameMacros** (``std::vector<std::string>``)
-  A vector of macros that should be interpreted as type declarations
-  instead of as function calls.
-
-  These are expected to be macros of the form:
-
-  .. code-block: c++
-
-    STACK_OF(...)
-
-  In the .clang-format configuration file, this can be configured like:
-
-  .. code-block: yaml
-
-    TypenameMacros: ['STACK_OF', 'LIST']
-
-  For example: OpenSSL STACK_OF, BSD LIST_ENTRY.
-
 **IncludeBlocks** (``IncludeBlocksStyle``)
   Dependent on the value, multiple ``#include`` blocks can be sorted
   as one and divided based on category.
 
   Possible values:
 
   * ``IBS_Preserve`` (in configuration: ``Preserve``)
     Sort each ``#include`` block separately.
**SpaceBeforeRangeBasedForLoopColon** (``bool``)
   If ``false``, spaces will be removed before range-based for loop
   colon.
 
   .. code-block:: c++
 
      true:                                  false:
      for (auto v : values) {}       vs.     for(auto v: values) {}
 
+**SpaceInEmptyBlock** (``bool``)
+  If ``true``, spaces may be inserted into ``{}``.
+
+  .. code-block:: c++
+
+     true:                                false:
+     void f() { }                   vs.   void f() {}
+     while (true) { }                     while (true) {}
+
 **SpaceInEmptyParentheses** (``bool``)
   If ``true``, spaces may be inserted into ``()``.
 
   .. code-block:: c++
 
      true:                                false:
      void f( ) {                    vs.   void f() {
        int x[] = {foo( ), bar( )};          int x[] = {foo(), bar()};
**StatementMacros** (``std::vector<std::string>``)
   added; sometimes this is not the case, and this allows to make
   clang-format aware of such cases.
 
   For example: Q_UNUSED
 
 **TabWidth** (``unsigned``)
   The number of columns used for tab stops.
 
+**TypenameMacros** (``std::vector<std::string>``)
+  A vector of macros that should be interpreted as type declarations
+  instead of as function calls.
+
+  These are expected to be macros of the form:
+
+  .. code-block:: c++
+
+    STACK_OF(...)
+
+  In the .clang-format configuration file, this can be configured like:
+
+  .. code-block:: yaml
+
+    TypenameMacros: ['STACK_OF', 'LIST']
+
+  For example: OpenSSL STACK_OF, BSD LIST_ENTRY.
+
 **UseTab** (``UseTabStyle``)
   The way to use tab characters in the resulting file.
 
   Possible values:
 
   * ``UT_Never`` (in configuration: ``Never``)
     Never use tab.
 

clang/include/clang/Format/Format.h

   /// If ``false``, spaces will be removed before range-based for loop
   /// colon.
   /// \code
   ///    true:                                  false:
   ///    for (auto v : values) {}       vs.     for(auto v: values) {}
   /// \endcode
   bool SpaceBeforeRangeBasedForLoopColon;
 
+  /// If ``true``, spaces may be inserted into ``{}``.
+  /// \code
+  ///    true:                                false:
+  ///    void f() { }                   vs.   void f() {}
+  ///    while (true) { }                     while (true) {}
+  /// \endcode
+  bool SpaceInEmptyBlock;
+
   /// If ``true``, spaces may be inserted into ``()``.
   /// \code
   ///    true:                                false:
   ///    void f( ) {                    vs.   void f() {
   ///      int x[] = {foo( ), bar( )};          int x[] = {foo(), bar()};
   ///      if (true) {                          if (true) {
   ///        f( );                                f();
   ///      }                                    }
return AccessModifierOffset == R.AccessModifierOffset &&
            SpaceBeforeAssignmentOperators == R.SpaceBeforeAssignmentOperators &&
            SpaceBeforeCpp11BracedList == R.SpaceBeforeCpp11BracedList &&
            SpaceBeforeCtorInitializerColon ==
                R.SpaceBeforeCtorInitializerColon &&
            SpaceBeforeInheritanceColon == R.SpaceBeforeInheritanceColon &&
            SpaceBeforeParens == R.SpaceBeforeParens &&
            SpaceBeforeRangeBasedForLoopColon ==
                R.SpaceBeforeRangeBasedForLoopColon &&
+           SpaceInEmptyBlock == R.SpaceInEmptyBlock &&
            SpaceInEmptyParentheses == R.SpaceInEmptyParentheses &&
            SpacesBeforeTrailingComments == R.SpacesBeforeTrailingComments &&
            SpacesInAngles == R.SpacesInAngles &&
            SpacesInContainerLiterals == R.SpacesInContainerLiterals &&
            SpacesInCStyleCastParentheses == R.SpacesInCStyleCastParentheses &&
            SpacesInParentheses == R.SpacesInParentheses &&
            SpacesInSquareBrackets == R.SpacesInSquareBrackets &&
            Standard == R.Standard && TabWidth == R.TabWidth &&

clang/lib/Format/Format.cpp

IO.mapOptional("SpaceBeforeCpp11BracedList",
                    Style.SpaceBeforeCpp11BracedList);
     IO.mapOptional("SpaceBeforeCtorInitializerColon",
                    Style.SpaceBeforeCtorInitializerColon);
     IO.mapOptional("SpaceBeforeInheritanceColon",
                    Style.SpaceBeforeInheritanceColon);
     IO.mapOptional("SpaceBeforeParens", Style.SpaceBeforeParens);
     IO.mapOptional("SpaceBeforeRangeBasedForLoopColon",
                    Style.SpaceBeforeRangeBasedForLoopColon);
+    IO.mapOptional("SpaceInEmptyBlock", Style.SpaceInEmptyBlock);
     IO.mapOptional("SpaceInEmptyParentheses", Style.SpaceInEmptyParentheses);
     IO.mapOptional("SpacesBeforeTrailingComments",
                    Style.SpacesBeforeTrailingComments);
     IO.mapOptional("SpacesInAngles", Style.SpacesInAngles);
     IO.mapOptional("SpacesInContainerLiterals",
                    Style.SpacesInContainerLiterals);
     IO.mapOptional("SpacesInCStyleCastParentheses",
                    Style.SpacesInCStyleCastParentheses);
FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.ObjCSpaceBeforeProtocolList = true;
   LLVMStyle.PointerAlignment = FormatStyle::PAS_Right;
   LLVMStyle.SpacesBeforeTrailingComments = 1;
   LLVMStyle.Standard = FormatStyle::LS_Cpp11;
   LLVMStyle.UseTab = FormatStyle::UT_Never;
   LLVMStyle.ReflowComments = true;
   LLVMStyle.SpacesInParentheses = false;
   LLVMStyle.SpacesInSquareBrackets = false;
+  LLVMStyle.SpaceInEmptyBlock = false;
   LLVMStyle.SpaceInEmptyParentheses = false;
   LLVMStyle.SpacesInContainerLiterals = true;
   LLVMStyle.SpacesInCStyleCastParentheses = false;
   LLVMStyle.SpaceAfterCStyleCast = false;
   LLVMStyle.SpaceAfterLogicalNot = false;
   LLVMStyle.SpaceAfterTemplateKeyword = true;
   LLVMStyle.SpaceBeforeCtorInitializerColon = true;
   LLVMStyle.SpaceBeforeInheritanceColon = true;
FormatStyle getWebKitStyle() {
   Style.ColumnLimit = 0;
   Style.FixNamespaceComments = false;
   Style.IndentWidth = 4;
   Style.NamespaceIndentation = FormatStyle::NI_Inner;
   Style.ObjCBlockIndentWidth = 4;
   Style.ObjCSpaceAfterProperty = true;
   Style.PointerAlignment = FormatStyle::PAS_Left;
   Style.SpaceBeforeCpp11BracedList = true;
+  Style.SpaceInEmptyBlock = true;
   return Style;
 }
 
 FormatStyle getGNUStyle() {
   FormatStyle Style = getLLVMStyle();
   Style.AlwaysBreakAfterDefinitionReturnType = FormatStyle::DRTBS_All;
   Style.AlwaysBreakAfterReturnType = FormatStyle::RTBS_AllDefinitions;
   Style.BreakBeforeBinaryOperators = FormatStyle::BOS_All;

clang/lib/Format/UnwrappedLineFormatter.cpp

tryMergeSimpleBlock(SmallVectorImpl<AnnotatedLine *>::const_iterator I,
     }
 
     if (Line.Last->is(tok::l_brace)) {
       FormatToken *Tok = I[1]->First;
       if (Tok->is(tok::r_brace) && !Tok->MustBreakBefore &&
           (Tok->getNextNonComment() == nullptr ||
            Tok->getNextNonComment()->is(tok::semi))) {
         // We merge empty blocks even if the line exceeds the column limit.
-        Tok->SpacesRequiredBefore = 0;
+        Tok->SpacesRequiredBefore = Style.SpaceInEmptyBlock ? 1 : 0;
         Tok->CanBreakBefore = true;
         return 1;
       } else if (Limit != 0 && !Line.startsWithNamespace() &&
                  !startsExternCBlock(Line)) {
         // We don't merge short records.
         FormatToken *RecordTok = Line.First;
         // Skip record modifiers.
         while (RecordTok->Next &&

clang/unittests/Format/FormatTest.cpp

EXPECT_EQ("#define A                                       \\\n"
                    "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx); }",
                    getGoogleStyle()));
 }
 
 TEST_F(FormatTest, PutEmptyBlocksIntoOneLine) {
   EXPECT_EQ("{}", format("{}"));
   verifyFormat("enum E {};");
   verifyFormat("enum E {}");
+  EXPECT_EQ("void f() { }", format("void f() {}", getWebKitStyle()));
+  FormatStyle Style = getLLVMStyle();
+  Style.AllowShortBlocksOnASingleLine = true;
+  Style.SpaceInEmptyBlock = true;
+  EXPECT_EQ("while (true) { }", format("while (true) {}", Style));
 }
 
 TEST_F(FormatTest, FormatBeginBlockEndMacros) {
   FormatStyle Style = getLLVMStyle();
   Style.MacroBlockBegin = "^[A-Z_]+_BEGIN$";
   Style.MacroBlockEnd = "^[A-Z_]+_END$";
   verifyFormat("FOO_BEGIN\n"
                "  FOO_ENTRY\n"
TEST_F(FormatTest, ParsesConfigurationBools) {
   CHECK_PARSE_BOOL(ObjCSpaceBeforeProtocolList);
   CHECK_PARSE_BOOL(Cpp11BracedListStyle);
   CHECK_PARSE_BOOL(ReflowComments);
   CHECK_PARSE_BOOL(SortIncludes);
   CHECK_PARSE_BOOL(SortUsingDeclarations);
   CHECK_PARSE_BOOL(SpacesInParentheses);
   CHECK_PARSE_BOOL(SpacesInSquareBrackets);
   CHECK_PARSE_BOOL(SpacesInAngles);
+  CHECK_PARSE_BOOL(SpaceInEmptyBlock);
   CHECK_PARSE_BOOL(SpaceInEmptyParentheses);
   CHECK_PARSE_BOOL(SpacesInContainerLiterals);
   CHECK_PARSE_BOOL(SpacesInCStyleCastParentheses);
   CHECK_PARSE_BOOL(SpaceAfterCStyleCast);
   CHECK_PARSE_BOOL(SpaceAfterTemplateKeyword);
   CHECK_PARSE_BOOL(SpaceAfterLogicalNot);
   CHECK_PARSE_BOOL(SpaceBeforeAssignmentOperators);
   CHECK_PARSE_BOOL(SpaceBeforeCpp11BracedList);