[clang-format] add an option to insert a space only for non-code block empty braces, not for empty parentheses #93634

khei4 · 2024-05-29T03:06:51Z

add Leave option, which doesn't modify any empty braces.

Note

I guess compatibility is important, but including braces in parens options might have been miss-leading. If more descriptive option name and desirable changes exist, I'm very happy to hear that :)

llvmbot · 2024-05-29T03:07:22Z

@llvm/pr-subscribers-clang-format

@llvm/pr-subscribers-clang

Author: Kohei Asano (khei4)

Changes

What

This patch introduces an option to insert a space between empty braces, especially for empty initializer.

Motivation

WebKit has its own .clang-format and clang-format has basedOnStyle: WebKit, but it's inconsistent with internal style checker script, at least for the empty initializers.
For example, the following line, tweaked from WebKit source code, would be checked by the script

        toImpl(listenerRef)-&gt;use( {} );

$ python Tools/Scripts/check-webkit-style
ERROR: Source/WebKit/UIProcess/Inspector/win/WebInspectorUIProxyWin.cpp:222:  Extra space after ( in function call  [whitespace/parens] [4]
ERROR: Source/WebKit/UIProcess/Inspector/win/WebInspectorUIProxyWin.cpp:222:  Extra space before )  [whitespace/parens] [2]
ERROR: Source/WebKit/UIProcess/Inspector/win/WebInspectorUIProxyWin.cpp:222:  Missing space inside { }.  [whitespace/braces] [5]

A space in empty braces is required, but one in (also for empty) parens isn't allowed.

Current clang-format could insert a space in empty parenthesis and block simultaneously by turning on SpacesInParensOptions.InEmptyParentheses, but formatting only braces couldn't be achieved.

So we want to insert a space only for braces.

Note

I guess compatibility is important, but including braces in parens options might have been miss-leading. If more descriptive option name and desirable changes exist, I'm very happy to hear that :)

Full diff: https://github.com/llvm/llvm-project/pull/93634.diff

6 Files Affected:

(modified) clang/docs/ClangFormatStyleOptions.rst (+13-1)
(modified) clang/include/clang/Format/Format.h (+17-4)
(modified) clang/lib/Format/Format.cpp (+1)
(modified) clang/lib/Format/TokenAnnotator.cpp (+5)
(modified) clang/unittests/Format/ConfigParseTest.cpp (+13-8)
(modified) clang/unittests/Format/FormatTest.cpp (+5)

diff --git a/clang/docs/ClangFormatStyleOptions.rst b/clang/docs/ClangFormatStyleOptions.rst
index 6d092219877f9..a1944eec8582b 100644
--- a/clang/docs/ClangFormatStyleOptions.rst
+++ b/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++
diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
index 274b45d1bc586..4482f7fb49788 100644
--- a/clang/include/clang/Format/Format.h
+++ b/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);
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index 9cba0c2614eef..efcc48b910718 100644
--- a/clang/lib/Format/Format.cpp
+++ b/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);
   }
 };
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 7c4c76a91f2c5..094c182c8d448 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/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))) {
diff --git a/clang/unittests/Format/ConfigParseTest.cpp b/clang/unittests/Format/ConfigParseTest.cpp
index 82e72f08ffb5e..c8918d4cec128 100644
--- a/clang/unittests/Format/ConfigParseTest.cpp
+++ b/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 = {};
 
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 2f0c0f0266774..f154941426f2c 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -14027,6 +14027,11 @@ TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
   SpaceBetweenBraces.SpacesInParens = FormatStyle::SIPO_Custom;
   SpaceBetweenBraces.SpacesInParensOptions.InEmptyParentheses = true;
   verifyFormat("vector< int > x{ };", SpaceBetweenBraces);
+  SpaceBetweenBraces.SpacesInParens = FormatStyle::SIPO_Custom;
+  SpaceBetweenBraces.SpacesInParensOptions.InEmptyParentheses = false;
+  SpaceBetweenBraces.SpacesInParensOptions.Other = false;
+  SpaceBetweenBraces.SpacesInParensOptions.InEmptyBraces = true;
+  verifyFormat("T x = { };\nf(x, { });\ng();", SpaceBetweenBraces);
 }
 
 TEST_F(FormatTest, FormatsBracedListsInColumnLayout) {

clang/docs/ClangFormatStyleOptions.rst

mydeveloperday

I think you might be missing a change in the == operator for the Style

clang/unittests/Format/FormatTest.cpp

clang/include/clang/Format/Format.h

github-actions · 2024-05-30T02:47:45Z

✅ With the latest revision this PR passed the C/C++ code formatter.

owenca · 2024-05-30T06:37:22Z

See #93635 (comment). Also, we need to deprecate SpaceInEmptyBlock.

khei4 · 2024-06-06T04:29:33Z

See #93635 (comment). Also, we need to deprecate SpaceInEmptyBlock.

@owenca
I added options. I'm grad if you take a look ;)

mydeveloperday

In general this looks ok, but lets see what @owenca and @HazardyKnusperkeks say

mydeveloperday · 2024-06-06T14:24:17Z

clang/docs/ClangFormatStyleOptions.rst

can these be Never/Always/Leave

clang/lib/Format/Format.cpp

mydeveloperday · 2024-06-06T14:27:10Z

clang/lib/Format/Format.cpp

can we confirm this matches their published style guide because we are about to change defaults

I believe this matches, but it might be miss-leading to specify only Block and Initlist, (although they are same with all braces). check-webkit-style script seems like to check whatever empty braces have a space inside of it.

self.assert_lint(' { }', '') self.assert_lint(' {}', 'Missing space inside { }. [whitespace/braces] [5]') self.assert_lint(' { }', 'Too many spaces inside { }. [whitespace/braces] [5]')

So adding SIEBO_Always and using it might be better. To double check, I will ask in WebKit slack also. Thanks!

IMO we need to go by the published WebKit coding style, not the script.

@owenca
Thank you. I found there are no entries about empty braces. I will consult on the WebKit mailing list about the inconsistency between Code Style Guideline and check-webkit-style script. I think it’s good to separate the WebKit Style fixes and empty braces options addition on this patch. Although I can’t still find how much this kind of inconsistency exist, I will file an issue if it’s necessary. :)

clang/unittests/Format/ConfigParseTest.cpp

owenca · 2024-06-10T00:51:09Z

See #93635 (comment).

@khei4 maybe an enum for SpaceInEmptyBraces with Always, Never, and Custom. (IMO Leave doesn't make sense.)

With Custom, a list of boolean suboptions e.g. Function, List, etc. can be set individually.

We have the following brace types now:

BlockLBrace
BracedListLBrace
ClassLBrace
ControlStatementLBrace
ElseLBrace
EnumLBrace
FunctionLBrace
InlineASMBrace
LambdaLBrace
NamespaceLBrace
ObjCBlockLBrace
RecordLBrace
RequiresExpressionLBrace
StructLBrace
SwitchExpressionLBrace
UnionLBrace

I would implement all that make sense or are applicable to WebKit.

khei4 · 2024-06-14T07:21:48Z

@owenca Thank you for the review!

@khei4 maybe an enum for SpaceInEmptyBraces with Always, Never, and Custom. (IMO Leave doesn't make sense.)

I make those variants. How do you think the behavior of config, which has only SpaceInEmptyBraces.SpacesInParensOptions.InEmptyParentheses = true; should be after this patch? I make Never default value now, so SpacesInParensOptions.InEmptyParentheses wouldn't insert a space into empty braces after this patch if it's without enabling SpaceInEmptyBraces

I would implement all that make sense or are applicable to WebKit.

TBH, I'm not sure how much braces should be classified on config, I will consult concretely, but WebKit style may be SpaceInEmptyBraces: Always. Can I leave them to you? Thank you!

khei4 · 2024-06-20T00:30:23Z

I confirmed the update of WebKit Code Style Guideline for empty braces. I make WebKit style insert a space in any empty braces. I also updated document by script.

mydeveloperday

You cannot remove options or you'll break everyone using that option right?

mydeveloperday · 2024-08-15T07:34:29Z

clang/include/clang/Format/Format.h

+  /// ``SpaceInEmptyBracesOptions`` to ``true``.
  /// \version 10
-  bool SpaceInEmptyBlock;
+  // bool SpaceInEmptyBlock;


sorry I don't understand are you removing this?

I was reviewing this PR and running into some issues related to https://reviews.llvm.org/D68415. I felt that we had to bite the bullet and add a new boolean option like the author did initially.

Actually, we might be able to support the following enumerated values:

Always (WebKit default)

Block (which would deprecate SpaceInEmptyBlock)

Leave (to be implemented in this patch or a follow-up patch)

Never (LLVM default)

clang/docs/ClangFormatStyleOptions.rst

khei4 · 2025-01-11T15:18:56Z

rebased but still required to be tested and fix again

owenca · 2025-01-12T06:01:00Z

rebased but still required to be tested and fix again

See #93634 (comment).

owenca · 2025-08-17T19:59:49Z

See #153765.

owenca · 2025-10-13T05:35:56Z

@khei4 can you close this pull request?

khei4 · 2025-10-13T06:02:27Z

@owenca Thank you! I'm sorry for not responding.

llvmbot added clang Clang issues not falling into any other category clang-format labels May 29, 2024

khei4 requested review from HazardyKnusperkeks, mydeveloperday and owenca May 29, 2024 03:09

khei4 changed the title ~~[clang-format] add an option to insert a space only for non-code block empty braces~~ [clang-format] add an option to insert a space only for non-code block empty braces, not for empty parentheses May 29, 2024

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owenca mentioned this pull request Jun 19, 2024

[clang-format] Correctly annotate l_brace after TypenameMacro #96026

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khei4 marked this pull request as draft January 11, 2025 15:19

change version to 20

846a6ac

khei4 closed this Oct 13, 2025

[clang-format] add an option to insert a space only for non-code block empty braces, not for empty parentheses #93634

[clang-format] add an option to insert a space only for non-code block empty braces, not for empty parentheses #93634

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