[clang-format] add an option to insert a space only for empty braces

Co-authored-by: Björn Schäpers <github@hazardy.de>

Author: khei4

clang/docs/ClangFormatStyleOptions.rst

@@ -6237,18 +6237,30 @@ the configuration (without a prefix: ``Auto``).
        true:                                  false:
        x = ( int32 )y                 vs.     x = (int32)y
 
-  * ``bool InEmptyParentheses`` Put a space in parentheses only if the parentheses are empty i.e. '()'
+  * ``bool InEmptyParentheses`` Put a space in parentheses and braces only if they are empty i.e. '()' or '{}'
 
     .. code-block:: c++
 
        true:                                false:
        void f( ) {                    vs.   void f() {
          int x[] = {foo( ), bar( )};          int x[] = {foo(), bar()};
+         T a = { };                           T a = {};
          if (true) {                          if (true) {
            f( );                                f();
          }                                    }
        }                                    }
 
+  * ``bool InEmptyBraces`` Put a space in *only* braces, not for parentheses, only if the braces are empty i.e. '{}'
+
+    .. code-block:: c++
+
+       true:                                false:
+       void f() {                     vs.   void f() {
+         T x = {};                            T x = { };
+         g(x, {});                            g(x, { });
+       }                                    }
+
+
   * ``bool Other`` Put a space in parentheses not covered by preceding options.
 
     .. code-block:: c++

clang/include/clang/Format/Format.h

@@ -4673,6 +4673,17 @@ struct FormatStyle {
     ///    }                                    }
     /// \endcode
     bool InEmptyParentheses;
+    /// Put a space in brackets only if the parentheses are empty i.e. '()'
+    /// \code
+    ///    true:                                false:
+    ///    void f( ) {                    vs.   void f() {
+    ///      int x[] = {foo( ), bar( )};          int x[] = {foo(), bar()};
+    ///      if (true) {                          if (true) {
+    ///        f( );                                f();
+    ///      }                                    }
+    ///    }                                    }
+    /// \endcode
+    bool InEmptyBraces;
     /// Put a space in parentheses not covered by preceding options.
     /// \code
     ///    true:                                  false:
@@ -4682,18 +4693,20 @@ struct FormatStyle {
 
     SpacesInParensCustom()
         : InConditionalStatements(false), InCStyleCasts(false),
-          InEmptyParentheses(false), Other(false) {}
+          InEmptyParentheses(false), InEmptyBraces(false), Other(false) {}
 
     SpacesInParensCustom(bool InConditionalStatements, bool InCStyleCasts,
-                         bool InEmptyParentheses, bool Other)
+                         bool InEmptyParentheses, bool InEmptyBraces,
+                         bool Other)
         : InConditionalStatements(InConditionalStatements),
           InCStyleCasts(InCStyleCasts), InEmptyParentheses(InEmptyParentheses),
-          Other(Other) {}
+          InEmptyBraces(InEmptyBraces), Other(Other) {}
 
     bool operator==(const SpacesInParensCustom &R) const {
       return InConditionalStatements == R.InConditionalStatements &&
              InCStyleCasts == R.InCStyleCasts &&
-             InEmptyParentheses == R.InEmptyParentheses && Other == R.Other;
+             InEmptyParentheses == R.InEmptyParentheses &&
+             InEmptyBraces == R.InEmptyBraces && Other == R.Other;
     }
     bool operator!=(const SpacesInParensCustom &R) const {
       return !(*this == R);

clang/lib/Format/Format.cpp

@@ -723,6 +723,7 @@ template <> struct MappingTraits<FormatStyle::SpacesInParensCustom> {
     IO.mapOptional("InCStyleCasts", Spaces.InCStyleCasts);
     IO.mapOptional("InConditionalStatements", Spaces.InConditionalStatements);
     IO.mapOptional("InEmptyParentheses", Spaces.InEmptyParentheses);
+    IO.mapOptional("InEmptyBraces", Spaces.InEmptyBraces);
     IO.mapOptional("Other", Spaces.Other);
   }
 };
@@ -1864,6 +1865,9 @@ FormatStyle getWebKitStyle() {
   Style.PointerAlignment = FormatStyle::PAS_Left;
   Style.SpaceBeforeCpp11BracedList = true;
   Style.SpaceInEmptyBlock = true;
+  Style.SpacesInParensOptions.InEmptyParentheses = false;
+  Style.SpacesInParensOptions.Other = false;
+  Style.SpacesInParensOptions.InEmptyBraces = true;
   return Style;
 }
 

clang/lib/Format/TokenAnnotator.cpp

@@ -4341,6 +4341,11 @@ bool TokenAnnotator::spaceRequiredBetween(const AnnotatedLine &Line,
       Right.MatchingParen == &Left && Line.Children.empty()) {
     return Style.SpaceInEmptyBlock;
   }
+  if (Style.SpacesInParensOptions.InEmptyBraces &&
+      (Left.is(tok::l_brace) && Left.isNot(BK_Block) &&
+       Right.is(tok::r_brace) && Right.isNot(BK_Block))) {
+    return Style.SpacesInParensOptions.InEmptyBraces;
+  }
   if ((Left.is(tok::l_paren) && Right.is(tok::r_paren)) ||
       (Left.is(tok::l_brace) && Left.isNot(BK_Block) &&
        Right.is(tok::r_brace) && Right.isNot(BK_Block))) {

clang/unittests/Format/ConfigParseTest.cpp

@@ -238,6 +238,7 @@ TEST(ConfigParseTest, ParsesConfigurationBools) {
   CHECK_PARSE_NESTED_BOOL(SpacesInParensOptions, InCStyleCasts);
   CHECK_PARSE_NESTED_BOOL(SpacesInParensOptions, InConditionalStatements);
   CHECK_PARSE_NESTED_BOOL(SpacesInParensOptions, InEmptyParentheses);
+  CHECK_PARSE_NESTED_BOOL(SpacesInParensOptions, InEmptyBraces);
   CHECK_PARSE_NESTED_BOOL(SpacesInParensOptions, Other);
 }
 
@@ -619,20 +620,24 @@ TEST(ConfigParseTest, ParsesConfiguration) {
               FormatStyle::SIPO_Custom);
   Style.SpacesInParens = FormatStyle::SIPO_Never;
   Style.SpacesInParensOptions = {};
-  CHECK_PARSE("SpacesInParentheses: true", SpacesInParensOptions,
-              FormatStyle::SpacesInParensCustom(true, false, false, true));
+  CHECK_PARSE(
+      "SpacesInParentheses: true", SpacesInParensOptions,
+      FormatStyle::SpacesInParensCustom(true, false, false, false, true));
   Style.SpacesInParens = FormatStyle::SIPO_Never;
   Style.SpacesInParensOptions = {};
-  CHECK_PARSE("SpacesInConditionalStatement: true", SpacesInParensOptions,
-              FormatStyle::SpacesInParensCustom(true, false, false, false));
+  CHECK_PARSE(
+      "SpacesInConditionalStatement: true", SpacesInParensOptions,
+      FormatStyle::SpacesInParensCustom(true, false, false, false, false));
   Style.SpacesInParens = FormatStyle::SIPO_Never;
   Style.SpacesInParensOptions = {};
-  CHECK_PARSE("SpacesInCStyleCastParentheses: true", SpacesInParensOptions,
-              FormatStyle::SpacesInParensCustom(false, true, false, false));
+  CHECK_PARSE(
+      "SpacesInCStyleCastParentheses: true", SpacesInParensOptions,
+      FormatStyle::SpacesInParensCustom(false, true, false, false, false));
   Style.SpacesInParens = FormatStyle::SIPO_Never;
   Style.SpacesInParensOptions = {};
-  CHECK_PARSE("SpaceInEmptyParentheses: true", SpacesInParensOptions,
-              FormatStyle::SpacesInParensCustom(false, false, true, false));
+  CHECK_PARSE(
+      "SpaceInEmptyParentheses: true", SpacesInParensOptions,
+      FormatStyle::SpacesInParensCustom(false, false, true, false, false));
   Style.SpacesInParens = FormatStyle::SIPO_Never;
   Style.SpacesInParensOptions = {};
 

clang/unittests/Format/FormatTest.cpp

@@ -14027,6 +14027,16 @@ TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
   SpaceBetweenBraces.SpacesInParens = FormatStyle::SIPO_Custom;
   SpaceBetweenBraces.SpacesInParensOptions.InEmptyParentheses = true;
   verifyFormat("vector< int > x{ };", SpaceBetweenBraces);
+
+  SpaceBetweenBraces.SpacesInParensOptions.InEmptyParentheses = false;
+  SpaceBetweenBraces.SpacesInParensOptions.Other = false;
+  SpaceBetweenBraces.SpacesInParensOptions.InEmptyBraces = true;
+  // This achieves braces-only spacing required by WebKit style.
+  verifyFormat("T x = { };\n"
+               "toImpl(listenerRef)\n"
+               "    ->use({ });\n"
+               "g();",
+               SpaceBetweenBraces);
 }
 
 TEST_F(FormatTest, FormatsBracedListsInColumnLayout) {