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[clang-format] Add option to separate comment alignment between ... #165033

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0bce319
[clang-format] Add option to separate comment alignment between ...
HazardyKnusperkeks Oct 21, 2025
a110811
Extent tests
HazardyKnusperkeks Oct 28, 2025
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10 changes: 10 additions & 0 deletions clang/docs/ClangFormatStyleOptions.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1701,6 +1701,16 @@ the configuration (without a prefix: ``Auto``).

int abcdef; // but this isn't

* ``bool AlignPPAndNotPP`` If comments following preprocessor directive should be aligned with
comments that don't.

.. code-block:: c++

true: false:
#define A // Comment vs. #define A // Comment
#define AB // Aligned #define AB // Aligned
int i; // Aligned int i; // Not aligned


.. _AllowAllArgumentsOnNextLine:

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1 change: 1 addition & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -609,6 +609,7 @@ clang-format
literals.
- Add ``Leave`` suboption to ``IndentPPDirectives``.
- Add ``AllowBreakBeforeQtProperty`` option.
- Add ``AlignPPAndNotPP`` suboption to ``AlignTrailingComments``.

libclang
--------
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12 changes: 11 additions & 1 deletion clang/include/clang/Format/Format.h
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Expand Up @@ -622,9 +622,19 @@ struct FormatStyle {
/// int abcdef; // but this isn't
/// \endcode
unsigned OverEmptyLines;
/// If comments following preprocessor directive should be aligned with
/// comments that don't.
/// \code
/// true: false:
/// #define A // Comment vs. #define A // Comment
/// #define AB // Aligned #define AB // Aligned
/// int i; // Aligned int i; // Not aligned
/// \endcode
bool AlignPPAndNotPP;

bool operator==(const TrailingCommentsAlignmentStyle &R) const {
return Kind == R.Kind && OverEmptyLines == R.OverEmptyLines;
return Kind == R.Kind && OverEmptyLines == R.OverEmptyLines &&
AlignPPAndNotPP == R.AlignPPAndNotPP;
}
bool operator!=(const TrailingCommentsAlignmentStyle &R) const {
return !(*this == R);
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12 changes: 7 additions & 5 deletions clang/lib/Format/Format.cpp
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Expand Up @@ -869,27 +869,28 @@ template <> struct MappingTraits<FormatStyle::TrailingCommentsAlignmentStyle> {
FormatStyle::TrailingCommentsAlignmentStyle &Value) {
IO.enumCase(Value, "Leave",
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Leave, 0}));
{FormatStyle::TCAS_Leave, 0, true}));

IO.enumCase(Value, "Always",
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Always, 0}));
{FormatStyle::TCAS_Always, 0, true}));

IO.enumCase(Value, "Never",
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Never, 0}));
{FormatStyle::TCAS_Never, 0, true}));

// For backwards compatibility
IO.enumCase(Value, "true",
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Always, 0}));
{FormatStyle::TCAS_Always, 0, true}));
IO.enumCase(Value, "false",
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Never, 0}));
{FormatStyle::TCAS_Never, 0, true}));
}

static void mapping(IO &IO,
FormatStyle::TrailingCommentsAlignmentStyle &Value) {
IO.mapOptional("AlignPPAndNotPP", Value.AlignPPAndNotPP);
IO.mapOptional("Kind", Value.Kind);
IO.mapOptional("OverEmptyLines", Value.OverEmptyLines);
}
Expand Down Expand Up @@ -1578,6 +1579,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
LLVMStyle.AlignTrailingComments = {};
LLVMStyle.AlignTrailingComments.Kind = FormatStyle::TCAS_Always;
LLVMStyle.AlignTrailingComments.OverEmptyLines = 0;
LLVMStyle.AlignTrailingComments.AlignPPAndNotPP = true;
LLVMStyle.AllowAllArgumentsOnNextLine = true;
LLVMStyle.AllowAllParametersOfDeclarationOnNextLine = true;
LLVMStyle.AllowBreakBeforeNoexceptSpecifier = FormatStyle::BBNSS_Never;
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18 changes: 17 additions & 1 deletion clang/lib/Format/WhitespaceManager.cpp
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Expand Up @@ -997,9 +997,13 @@ void WhitespaceManager::alignTrailingComments() {
return;

const int Size = Changes.size();
if (Size == 0)
return;

int MinColumn = 0;
int StartOfSequence = 0;
bool BreakBeforeNext = false;
bool IsInPP = Changes.front().Tok->Tok.is(tok::hash);
int NewLineThreshold = 1;
if (Style.AlignTrailingComments.Kind == FormatStyle::TCAS_Always)
NewLineThreshold = Style.AlignTrailingComments.OverEmptyLines + 1;
Expand All @@ -1008,7 +1012,19 @@ void WhitespaceManager::alignTrailingComments() {
auto &C = Changes[I];
if (C.StartOfBlockComment)
continue;
Newlines += C.NewlinesBefore;
if (C.NewlinesBefore != 0) {
Newlines += C.NewlinesBefore;
const bool WasInPP = std::exchange(
IsInPP, C.Tok->Tok.is(tok::hash) || (IsInPP && C.IsTrailingComment) ||
C.ContinuesPPDirective);
if (IsInPP != WasInPP && !Style.AlignTrailingComments.AlignPPAndNotPP) {
alignTrailingComments(StartOfSequence, I, MinColumn);
MinColumn = 0;
MaxColumn = INT_MAX;
StartOfSequence = I;
Newlines = 0;
}
}
if (!C.IsTrailingComment)
continue;

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11 changes: 6 additions & 5 deletions clang/unittests/Format/ConfigParseTest.cpp
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Expand Up @@ -576,20 +576,20 @@ TEST(ConfigParseTest, ParsesConfiguration) {

CHECK_PARSE("AlignTrailingComments: Leave", AlignTrailingComments,
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Leave, 0}));
{FormatStyle::TCAS_Leave, 0, true}));
CHECK_PARSE("AlignTrailingComments: Always", AlignTrailingComments,
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Always, 0}));
{FormatStyle::TCAS_Always, 0, true}));
CHECK_PARSE("AlignTrailingComments: Never", AlignTrailingComments,
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Never, 0}));
{FormatStyle::TCAS_Never, 0, true}));
// For backwards compatibility
CHECK_PARSE("AlignTrailingComments: true", AlignTrailingComments,
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Always, 0}));
{FormatStyle::TCAS_Always, 0, true}));
CHECK_PARSE("AlignTrailingComments: false", AlignTrailingComments,
FormatStyle::TrailingCommentsAlignmentStyle(
{FormatStyle::TCAS_Never, 0}));
{FormatStyle::TCAS_Never, 0, true}));
CHECK_PARSE_NESTED_VALUE("Kind: Always", AlignTrailingComments, Kind,
FormatStyle::TCAS_Always);
CHECK_PARSE_NESTED_VALUE("Kind: Never", AlignTrailingComments, Kind,
Expand All @@ -598,6 +598,7 @@ TEST(ConfigParseTest, ParsesConfiguration) {
FormatStyle::TCAS_Leave);
CHECK_PARSE_NESTED_VALUE("OverEmptyLines: 1234", AlignTrailingComments,
OverEmptyLines, 1234u);
CHECK_PARSE_NESTED_BOOL(AlignTrailingComments, AlignPPAndNotPP);

Style.UseTab = FormatStyle::UT_ForIndentation;
CHECK_PARSE("UseTab: Never", UseTab, FormatStyle::UT_Never);
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60 changes: 60 additions & 0 deletions clang/unittests/Format/FormatTestComments.cpp
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Expand Up @@ -3501,6 +3501,66 @@ TEST_F(FormatTestComments, DontAlignOverScope) {
"int foobar; // group");
}

TEST_F(FormatTestComments, DontAlignOverPPDirective) {
auto Style = getLLVMStyle();
Style.AlignTrailingComments.AlignPPAndNotPP = false;

verifyFormat("int i; // Aligned\n"
"int long; // with this\n"
"#define FOO // only aligned\n"
"#define LOOONG // with other pp directives\n"
"int loooong; // new alignment",
"int i;//Aligned\n"
"int long;//with this\n"
"#define FOO //only aligned\n"
"#define LOOONG //with other pp directives\n"
"int loooong; //new alignment",
Style);

verifyFormat("#define A // Comment\n"
"#define AB // Comment",
Style);

Style.ColumnLimit = 30;
verifyNoChange("#define A // Comment\n"
" // Continued\n"
"int i = 0; // New Stuff\n"
" // Continued\n"
"#define Func(X) \\\n"
" X(); \\\n"
" X(); // Comment\n"
" // Continued\n"
"long loong = 1; // Dont align",
Style);

verifyFormat("#define A // Comment that\n"
" // would wrap\n"
"#define FOO // For the\n"
" // alignment\n"
"#define B // Also\n"
" // aligned",
"#define A // Comment that would wrap\n"
"#define FOO // For the alignment\n"
"#define B // Also\n"
" // aligned",
Style);

Style.AlignTrailingComments.OverEmptyLines = 1;
verifyNoChange("#define A // Comment\n"
"\n"
" // Continued\n"
"int i = 0; // New Stuff\n"
"\n"
" // Continued\n"
"#define Func(X) \\\n"
" X(); \\\n"
" X(); // Comment\n"
"\n"
" // Continued\n"
"long loong = 1; // Dont align",
Style);
}

TEST_F(FormatTestComments, AlignsBlockCommentDecorations) {
EXPECT_EQ("/*\n"
" */",
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