[clang] [clang-format] Add AfterComma option for BreakConstructorInitializers (PR #180541)
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Mon Feb 9 07:23:24 PST 2026
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-format
Author: Perceval Anichini (maneex)
<details>
<summary>Changes</summary>
This patch introduces a new `AfterComma` value for the `BreakConstructorInitializers` style option. This style keeps the constructor initializer colon on the same line as the constructor declaration and breaks after each comma in the initializer list.
Example formatting:
```cpp
Constructor() : initializer1(),
initializer2()
```
This style provides an alternative to the existing BeforeColon, BeforeComma, and AfterColon options, allowing developers to maintain the colon on the constructor line while placing each initializer on its own line after commas.
---
Full diff: https://github.com/llvm/llvm-project/pull/180541.diff
8 Files Affected:
- (modified) clang/docs/ClangFormatStyleOptions.rst (+8)
- (modified) clang/docs/ReleaseNotes.rst (+3-1)
- (modified) clang/include/clang/Format/Format.h (+7-1)
- (modified) clang/lib/Format/ContinuationIndenter.cpp (+2-1)
- (modified) clang/lib/Format/Format.cpp (+1)
- (modified) clang/lib/Format/TokenAnnotator.cpp (+13-3)
- (modified) clang/unittests/Format/ConfigParseTest.cpp (+2)
- (modified) clang/unittests/Format/FormatTest.cpp (+59)
``````````diff
diff --git a/clang/docs/ClangFormatStyleOptions.rst b/clang/docs/ClangFormatStyleOptions.rst
index 378a0c591d747..437f559fc0395 100644
--- a/clang/docs/ClangFormatStyleOptions.rst
+++ b/clang/docs/ClangFormatStyleOptions.rst
@@ -3686,6 +3686,14 @@ the configuration (without a prefix: ``Auto``).
initializer1(),
initializer2()
+ * ``BCIS_AfterComma`` (in configuration: ``AfterComma``)
+ Break constructor initializers only after the commas.
+
+ .. code-block:: c++
+
+ Constructor() : initializer1(),
+ initializer2()
+
.. _BreakFunctionDefinitionParameters:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a1bb1bd2467b7..8620ae4f61ae6 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -360,7 +360,9 @@ AST Matchers
clang-format
------------
-- Add ``ObjCSpaceAfterMethodDeclarationPrefix`` option to control space between the
+- Add ``AfterComma`` value to ``BreakConstructorInitializers`` to allow breaking
+ constructor initializers after commas, keeping the colon on the same line.
+- Add ``ObjCSpaceAfterMethodDeclarationPrefix`` option to control space between the
'-'/'+' and the return type in Objective-C method declarations
libclang
diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
index 57ae14304b969..ca0bd47d10613 100644
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -2477,7 +2477,13 @@ struct FormatStyle {
/// initializer1(),
/// initializer2()
/// \endcode
- BCIS_AfterColon
+ BCIS_AfterColon,
+ /// Break constructor initializers only after the commas.
+ /// \code
+ /// Constructor() : initializer1(),
+ /// initializer2()
+ /// \endcode
+ BCIS_AfterComma
};
/// The break constructor initializers style to use.
diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index 1272bb72d423f..f1edd71df73fa 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -510,7 +510,8 @@ bool ContinuationIndenter::mustBreak(const LineState &State) {
Style.BreakConstructorInitializers == FormatStyle::BCIS_AfterColon
? Previous
: Current;
- if (BreakConstructorInitializersToken.is(TT_CtorInitializerColon) &&
+ if (Style.BreakConstructorInitializers != FormatStyle::BCIS_AfterComma &&
+ BreakConstructorInitializersToken.is(TT_CtorInitializerColon) &&
(State.Column + State.Line->Last->TotalLength - Previous.TotalLength >
getColumnLimit(State) ||
CurrentState.BreakBeforeParameter) &&
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index 1e68de531791f..738e99dbb56a8 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -282,6 +282,7 @@ struct ScalarEnumerationTraits<FormatStyle::BreakConstructorInitializersStyle> {
IO.enumCase(Value, "BeforeColon", FormatStyle::BCIS_BeforeColon);
IO.enumCase(Value, "BeforeComma", FormatStyle::BCIS_BeforeComma);
IO.enumCase(Value, "AfterColon", FormatStyle::BCIS_AfterColon);
+ IO.enumCase(Value, "AfterComma", FormatStyle::BCIS_AfterComma);
}
};
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index b1c1afbf8684d..b98bc54c6eb98 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -5962,6 +5962,11 @@ bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
Left.isOneOf(TT_CtorInitializerColon, TT_CtorInitializerComma)) {
return true;
}
+
+ if (Style.BreakConstructorInitializers == FormatStyle::BCIS_AfterComma &&
+ Left.is(TT_CtorInitializerComma)) {
+ return true;
+ }
}
if (Style.PackConstructorInitializers < FormatStyle::PCIS_CurrentLine &&
Style.BreakConstructorInitializers == FormatStyle::BCIS_BeforeComma &&
@@ -6507,11 +6512,16 @@ bool TokenAnnotator::canBreakBefore(const AnnotatedLine &Line,
return true;
if (Left.is(TT_CtorInitializerColon)) {
- return Style.BreakConstructorInitializers == FormatStyle::BCIS_AfterColon &&
+ return (Style.BreakConstructorInitializers ==
+ FormatStyle::BCIS_AfterColon ||
+ Style.BreakConstructorInitializers ==
+ FormatStyle::BCIS_AfterComma) &&
(!Right.isTrailingComment() || Right.NewlinesBefore > 0);
}
- if (Right.is(TT_CtorInitializerColon))
- return Style.BreakConstructorInitializers != FormatStyle::BCIS_AfterColon;
+ if (Right.is(TT_CtorInitializerColon)) {
+ return Style.BreakConstructorInitializers != FormatStyle::BCIS_AfterColon &&
+ Style.BreakConstructorInitializers != FormatStyle::BCIS_AfterComma;
+ }
if (Left.is(TT_CtorInitializerComma) &&
Style.BreakConstructorInitializers == FormatStyle::BCIS_BeforeComma) {
return false;
diff --git a/clang/unittests/Format/ConfigParseTest.cpp b/clang/unittests/Format/ConfigParseTest.cpp
index 0a116b770f52a..bea6b54883265 100644
--- a/clang/unittests/Format/ConfigParseTest.cpp
+++ b/clang/unittests/Format/ConfigParseTest.cpp
@@ -466,6 +466,8 @@ TEST(ConfigParseTest, ParsesConfiguration) {
BreakConstructorInitializers, FormatStyle::BCIS_BeforeComma);
CHECK_PARSE("BreakConstructorInitializers: AfterColon",
BreakConstructorInitializers, FormatStyle::BCIS_AfterColon);
+ CHECK_PARSE("BreakConstructorInitializers: AfterComma",
+ BreakConstructorInitializers, FormatStyle::BCIS_AfterComma);
CHECK_PARSE("BreakConstructorInitializers: BeforeColon",
BreakConstructorInitializers, FormatStyle::BCIS_BeforeColon);
// For backward compatibility:
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 33836e28289b4..0343b6fa9298e 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -8448,6 +8448,65 @@ TEST_F(FormatTest, BreakConstructorInitializersAfterColon) {
Style);
}
+TEST_F(FormatTest, BreakConstructorInitializersAfterComma) {
+ FormatStyle Style = getLLVMStyle();
+ Style.BreakConstructorInitializers = FormatStyle::BCIS_AfterComma;
+
+ // Short initializer fits on one line.
+ verifyFormat("Constructor() : Initializer(FitsOnTheLine) {}", Style);
+
+ // Multiple short initializers fit on one line.
+ verifyFormat("Constructor() : a(a), b(b), c(c) {}", Style);
+
+ // One per line with PackConstructorInitializers: Never.
+ Style.PackConstructorInitializers = FormatStyle::PCIS_Never;
+ verifyFormat("SomeClass::Constructor() : aaaaaaaaaaaaa(aaaaaaaaaaaaaa),\n"
+ " aaaaaaaaaaaaa(aaaaaaaaaaaaaa),\n"
+ " aaaaaaaaaaaaa(aaaaaaaaaaaaaa) {}",
+ Style);
+
+ // Long class name with parameters wrapping.
+ verifyFormat("SomeClassWithALongName::Constructor(\n"
+ " int aaaaaaaaaaaaaaaaaaaaaaaa,\n"
+ " int bbbbbbbbbbbbb) : aaaaaaaaaaaaaaaaaaaa(a),\n"
+ " bbbbbbbbbbbbbbbbbbbbb(b) {}",
+ Style);
+
+ // CurrentLine packing.
+ Style.PackConstructorInitializers = FormatStyle::PCIS_CurrentLine;
+ verifyFormat("SomeClass::Constructor() : aaaaaaaaaaaaa(aaaaaaaaaaaaaa),\n"
+ " aaaaaaaaaaaaa(aaaaaaaaaaaaaa),\n"
+ " aaaaaaaaaaaaa(aaaaaaaaaaaaaa) {}",
+ Style);
+
+ // BinPack packing.
+ Style.PackConstructorInitializers = FormatStyle::PCIS_BinPack;
+ verifyFormat("SomeClass::Constructor() : aaaaaaaaaaaaa(aaaaaaaaaaaaaa),\n"
+ " aaaaaaaaaaaaaaa(aaaaaaaaaaaa) {}",
+ Style);
+
+ // NextLine packing.
+ Style.PackConstructorInitializers = FormatStyle::PCIS_NextLine;
+ verifyFormat("SomeClass::Constructor() : aaaaaaaaaaaaa(aaaaaaaaaaaaaa),\n"
+ " aaaaaaaaaaaaaaa(aaaaaaaaaaaa) {}",
+ Style);
+
+ // NextLineOnly packing.
+ Style.PackConstructorInitializers = FormatStyle::PCIS_NextLineOnly;
+ verifyFormat("SomeClass::Constructor() : aaaaaaaaaaaaa(aaaaaaaaaaaaaa),\n"
+ " aaaaaaaaaaaaaaa(aaaaaaaaaaaa) {}",
+ Style);
+
+ // ColumnLimit = 0 preserves input.
+ Style.ColumnLimit = 0;
+ Style.PackConstructorInitializers = FormatStyle::PCIS_CurrentLine;
+ verifyFormat("SomeClass::Constructor() : a(a), b(b), c(c) {}", Style);
+ verifyNoChange("SomeClass::Constructor() : a(a),\n"
+ " b(b),\n"
+ " c(c) {}",
+ Style);
+}
+
#ifndef EXPENSIVE_CHECKS
// Expensive checks enables libstdc++ checking which includes validating the
// state of ranges used in std::priority_queue - this blows out the
``````````
</details>
https://github.com/llvm/llvm-project/pull/180541
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