rdwampler created this revision.
rdwampler added reviewers: djasper, klimek.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
This option `AllowShortLambdasOnASingleLine` similar to the other `AllowShort*`
options, but applied to C++ lambdas.
I considered making this dependent on `AllowShortFunctionsOnASingleLine`, but
could not think of how the breaking should be behave when the option is set to
`Inline` and `InlineOnly`.
I could not find a specific coding style that requires short lambdas to
//always// break on a new line, but I do think it's fairly common practice.
Also, I note that the patch: https://reviews.llvm.org/D44609 attempts to add an
option to allow formatting lambda using the Allman style braces. Here is a
coding style that requires Allman style braces, but allows lambdas to be on
single line if they are short. So, maybe this option would be required to
handle this situation?
Addresses: https://bugs.llvm.org//show_bug.cgi?id=32151
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D57687
Files:
clang/docs/ClangFormatStyleOptions.rst
clang/include/clang/Format/Format.h
clang/lib/Format/Format.cpp
clang/lib/Format/FormatToken.h
clang/lib/Format/TokenAnnotator.cpp
clang/lib/Format/UnwrappedLineParser.cpp
clang/unittests/Format/FormatTest.cpp
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -11954,6 +11954,30 @@
" aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa> {\n"
" //\n"
" });");
+
+ FormatStyle DoNotMerge = getLLVMStyle();
+ DoNotMerge.AllowShortLambdasOnASingleLine = FormatStyle::SLS_None;
+ verifyFormat("auto c = []() {\n"
+ " return b;\n"
+ "};",
+ "auto c = []() { return b; };", DoNotMerge);
+ verifyFormat("auto c = []() {\n"
+ "};",
+ " auto c = []() {};", DoNotMerge);
+
+ FormatStyle MergeEmptyOnly = getLLVMStyle();
+ MergeEmptyOnly.AllowShortLambdasOnASingleLine = FormatStyle::SLS_Empty;
+ verifyFormat("auto c = []() {\n"
+ " return b;\n"
+ "};",
+ "auto c = []() {\n"
+ " return b;\n"
+ " };",
+ MergeEmptyOnly);
+ verifyFormat("auto c = []() {};",
+ "auto c = []() {\n"
+ "};",
+ MergeEmptyOnly);
}
TEST_F(FormatTest, EmptyLinesInLambdas) {
Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -1433,6 +1433,7 @@
return true;
}
}
+ FormatTok->Type = TT_LambdaLBrace;
LSquare.Type = TT_LambdaLSquare;
parseChildBlock();
return true;
Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -365,7 +365,7 @@
// specifier parameter, although this is technically valid:
// [[foo(:)]]
if (AttrTok->is(tok::colon) ||
- AttrTok->startsSequence(tok::identifier, tok::identifier) ||
+ AttrTok->startsSequence(tok::identifier, tok::identifier) ||
AttrTok->startsSequence(tok::r_paren, tok::identifier))
return false;
if (AttrTok->is(tok::ellipsis))
@@ -1138,11 +1138,11 @@
// Reset token type in case we have already looked at it and then
// recovered from an error (e.g. failure to find the matching >).
- if (!CurrentToken->isOneOf(TT_LambdaLSquare, TT_ForEachMacro,
- TT_FunctionLBrace, TT_ImplicitStringLiteral,
- TT_InlineASMBrace, TT_JsFatArrow, TT_LambdaArrow,
- TT_OverloadedOperator, TT_RegexLiteral,
- TT_TemplateString, TT_ObjCStringLiteral))
+ if (!CurrentToken->isOneOf(
+ TT_LambdaLSquare, TT_LambdaLBrace, TT_ForEachMacro,
+ TT_FunctionLBrace, TT_ImplicitStringLiteral, TT_InlineASMBrace,
+ TT_JsFatArrow, TT_LambdaArrow, TT_OverloadedOperator,
+ TT_RegexLiteral, TT_TemplateString, TT_ObjCStringLiteral))
CurrentToken->Type = TT_Unknown;
CurrentToken->Role.reset();
CurrentToken->MatchingParen = nullptr;
@@ -2835,7 +2835,7 @@
// Returns 'true' if 'Tok' is a brace we'd want to break before in Allman style.
static bool isAllmanBrace(const FormatToken &Tok) {
return Tok.is(tok::l_brace) && Tok.BlockKind == BK_Block &&
- !Tok.isOneOf(TT_ObjCBlockLBrace, TT_DictLiteral);
+ !Tok.isOneOf(TT_ObjCBlockLBrace, TT_LambdaLBrace, TT_DictLiteral);
}
bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
@@ -2962,6 +2962,10 @@
(Line.startsWith(tok::kw_struct) && Style.BraceWrapping.AfterStruct);
if (Left.is(TT_ObjCBlockLBrace) && !Style.AllowShortBlocksOnASingleLine)
return true;
+ if (Left.is(TT_LambdaLBrace))
+ return Style.AllowShortLambdasOnASingleLine == FormatStyle::SLS_None ||
+ (!Left.Children.empty() &&
+ Style.AllowShortLambdasOnASingleLine == FormatStyle::SLS_Empty);
if ((Style.Language == FormatStyle::LK_Java ||
Style.Language == FormatStyle::LK_JavaScript) &&
Index: clang/lib/Format/FormatToken.h
===================================================================
--- clang/lib/Format/FormatToken.h
+++ clang/lib/Format/FormatToken.h
@@ -65,6 +65,7 @@
TYPE(JsTypeOptionalQuestion) \
TYPE(LambdaArrow) \
TYPE(LambdaLSquare) \
+ TYPE(LambdaLBrace) \
TYPE(LeadingJavaAnnotation) \
TYPE(LineComment) \
TYPE(MacroBlockBegin) \
Index: clang/lib/Format/Format.cpp
===================================================================
--- clang/lib/Format/Format.cpp
+++ clang/lib/Format/Format.cpp
@@ -106,6 +106,16 @@
}
};
+template <> struct ScalarEnumerationTraits<FormatStyle::ShortLambdaStyle> {
+ static void enumeration(IO &IO, FormatStyle::ShortLambdaStyle &Value) {
+ IO.enumCase(Value, "None", FormatStyle::SLS_None);
+ IO.enumCase(Value, "false", FormatStyle::SLS_None);
+ IO.enumCase(Value, "Empty", FormatStyle::SLS_Empty);
+ IO.enumCase(Value, "All", FormatStyle::SLS_All);
+ IO.enumCase(Value, "true", FormatStyle::SLS_All);
+ }
+};
+
template <> struct ScalarEnumerationTraits<FormatStyle::BinPackStyle> {
static void enumeration(IO &IO, FormatStyle::BinPackStyle &Value) {
IO.enumCase(Value, "Auto", FormatStyle::BPS_Auto);
@@ -328,6 +338,8 @@
Style.AllowShortCaseLabelsOnASingleLine);
IO.mapOptional("AllowShortFunctionsOnASingleLine",
Style.AllowShortFunctionsOnASingleLine);
+ IO.mapOptional("AllowShortLambdasOnASingleLine",
+ Style.AllowShortLambdasOnASingleLine);
IO.mapOptional("AllowShortIfStatementsOnASingleLine",
Style.AllowShortIfStatementsOnASingleLine);
IO.mapOptional("AllowShortLoopsOnASingleLine",
@@ -633,6 +645,7 @@
LLVMStyle.AllowShortBlocksOnASingleLine = false;
LLVMStyle.AllowShortCaseLabelsOnASingleLine = false;
LLVMStyle.AllowShortIfStatementsOnASingleLine = false;
+ LLVMStyle.AllowShortLambdasOnASingleLine = FormatStyle::SLS_All;
LLVMStyle.AllowShortLoopsOnASingleLine = false;
LLVMStyle.AlwaysBreakAfterReturnType = FormatStyle::RTBS_None;
LLVMStyle.AlwaysBreakAfterDefinitionReturnType = FormatStyle::DRTBS_None;
@@ -867,6 +880,7 @@
} else {
ChromiumStyle.AllowAllParametersOfDeclarationOnNextLine = false;
ChromiumStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_Inline;
+ ChromiumStyle.AllowShortLambdasOnASingleLine = FormatStyle::SLS_All;
ChromiumStyle.AllowShortIfStatementsOnASingleLine = false;
ChromiumStyle.AllowShortLoopsOnASingleLine = false;
ChromiumStyle.BinPackParameters = false;
Index: clang/include/clang/Format/Format.h
===================================================================
--- clang/include/clang/Format/Format.h
+++ clang/include/clang/Format/Format.h
@@ -241,6 +241,27 @@
/// single line.
ShortFunctionStyle AllowShortFunctionsOnASingleLine;
+ enum ShortLambdaStyle {
+ /// Never merge lambdas into a single line.
+ SLS_None,
+ /// Only merge empty lambdas.
+ /// \code
+ /// auto lambda = [](int a) {}
+ /// auto lambda2 = [](int a) {
+ /// return a };
+ /// \endcode
+ SLS_Empty,
+ /// Merge all lambdas fitting on a single line.
+ /// \code
+ /// auto lambda = [](int a) {}
+ /// auto lambda2 = [](int a) { return a; };
+ /// \endcode
+ SLS_All,
+ };
+ /// Dependent on the value, ``auto lambda []() { return 0; }`` can be put on a
+ /// single line.
+ ShortLambdaStyle AllowShortLambdasOnASingleLine = SLS_All;
+
/// If ``true``, ``if (a) return;`` can be put on a single line.
bool AllowShortIfStatementsOnASingleLine;
Index: clang/docs/ClangFormatStyleOptions.rst
===================================================================
--- clang/docs/ClangFormatStyleOptions.rst
+++ clang/docs/ClangFormatStyleOptions.rst
@@ -370,6 +370,31 @@
**AllowShortIfStatementsOnASingleLine** (``bool``)
If ``true``, ``if (a) return;`` can be put on a single line.
+**AllowShortLambdasOnASingleLine** (``ShortLambdaStyle``)
+ Dependent on the value, ```auto lambda = [](int a) { return a; };``` can be
+ put on a single line.
+
+ Possible values:
+
+ * ``SLS_None`` (in configuration: ``None``)
+ Never merge lambdas into a single line.
+
+ * ``SLS_Empty`` (in configuration: ``Empty``)
+ Only merge empty lambdas.
+
+ .. code-block:: c++
+
+ auto lambda = [](int a) {}
+ auto lambda2 = [](int a) { return a; };
+
+ * ``SLS_All`` (in configuration: ``All``)
+ Merge all lambdas fitting on a single line.
+
+ .. code-block:: c++
+
+ auto lambda = [](int a) {}
+ auto lambda2 = [](int a) { return a; };
+
**AllowShortLoopsOnASingleLine** (``bool``)
If ``true``, ``while (true) continue;`` can be put on a single
line.
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