[clang-format] Add BreakBeforeTemplateCloser option #118046
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@llvm/pr-subscribers-clang @llvm/pr-subscribers-clang-format Author: leijurv (leijurv) ChangesIn clang-format, multiline templates have the template<
typename Foo,
typename Bar,
typename Baz>
void foo() {I would like to add an option to put the template<
typename Foo,
typename Bar,
typename Baz
>
void foo() {My reasoning is that it reminds me of this style of braces: if (foo()) {
bar();}Most people agree this is better: if (foo()) {
bar();
}Full diff: https://github.com/llvm/llvm-project/pull/118046.diff 7 Files Affected:
diff --git a/clang/docs/ClangFormatStyleOptions.rst b/clang/docs/ClangFormatStyleOptions.rst
index 4be448171699ca..31ed9a10d7153d 100644
--- a/clang/docs/ClangFormatStyleOptions.rst
+++ b/clang/docs/ClangFormatStyleOptions.rst
@@ -3416,6 +3416,29 @@ the configuration (without a prefix: ``Auto``).
+
+.. _BreakBeforeTemplateClose:
+
+**BreakBeforeTemplateClose** (``Boolean``) :versionbadge:`clang-format 20` :ref:`¶ <BreakBeforeTemplateClose>`
+ If ``true``, a line break will be placed before the ``>`` in a multiline template declaration.
+
+ .. code-block:: c++
+
+ true:
+ template <
+ typename Foo,
+ typename Bar,
+ typename Baz
+ >
+
+ false:
+ template <
+ typename Foo,
+ typename Bar,
+ typename Baz>
+
+
+
.. _BreakBeforeTernaryOperators:
**BreakBeforeTernaryOperators** (``Boolean``) :versionbadge:`clang-format 3.7` :ref:`¶ <BreakBeforeTernaryOperators>`
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index e44aefa90ab386..867d4b5d8c3f18 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -976,6 +976,7 @@ clang-format
``Never``, and ``true`` to ``Always``.
- Adds ``RemoveEmptyLinesInUnwrappedLines`` option.
- Adds ``KeepFormFeed`` option and set it to ``true`` for ``GNU`` style.
+- Adds ``BreakBeforeTemplateClose`` option.
libclang
--------
diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
index 6383934afa2c40..bffd964f6aa8aa 100644
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -2248,6 +2248,25 @@ struct FormatStyle {
/// \version 16
BreakBeforeInlineASMColonStyle BreakBeforeInlineASMColon;
+ /// If ``true``, a line break will be placed before the ``>`` in a multiline
+ /// template declaration.
+ /// \code
+ /// true:
+ /// template <
+ /// typename Foo,
+ /// typename Bar,
+ /// typename Baz
+ /// >
+ ///
+ /// false:
+ /// template <
+ /// typename Foo,
+ /// typename Bar,
+ /// typename Baz>
+ /// \endcode
+ /// \version 20
+ bool BreakBeforeTemplateClose;
+
/// If ``true``, ternary operators will be placed after line breaks.
/// \code
/// true:
@@ -5184,6 +5203,7 @@ struct FormatStyle {
BreakBeforeBraces == R.BreakBeforeBraces &&
BreakBeforeConceptDeclarations == R.BreakBeforeConceptDeclarations &&
BreakBeforeInlineASMColon == R.BreakBeforeInlineASMColon &&
+ BreakBeforeTemplateClose == R.BreakBeforeTemplateClose &&
BreakBeforeTernaryOperators == R.BreakBeforeTernaryOperators &&
BreakBinaryOperations == R.BreakBinaryOperations &&
BreakConstructorInitializers == R.BreakConstructorInitializers &&
diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index aed86c1fb99551..0c77c18b3e7f48 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -382,10 +382,25 @@ bool ContinuationIndenter::canBreak(const LineState &State) {
return !State.NoLineBreak && !CurrentState.NoLineBreak;
}
+bool isMatchingBraceOnSameLine(const FormatToken *Token) {
+ if (!Token->MatchingParen)
+ return false;
+ const FormatToken *Matching = Token->MatchingParen;
+ const FormatToken *Current = Token;
+ while (Current && Current != Matching) {
+ if (Current->NewlinesBefore > 0)
+ return false;
+ Current = Current->Previous;
+ }
+ return true;
+}
+
bool ContinuationIndenter::mustBreak(const LineState &State) {
const FormatToken &Current = *State.NextToken;
const FormatToken &Previous = *Current.Previous;
const auto &CurrentState = State.Stack.back();
+ if (Current.ClosesTemplateDeclaration && Style.BreakBeforeTemplateClose)
+ return !isMatchingBraceOnSameLine(State.NextToken);
if (Style.BraceWrapping.BeforeLambdaBody && Current.CanBreakBefore &&
Current.is(TT_LambdaLBrace) && Previous.isNot(TT_LineComment)) {
auto LambdaBodyLength = getLengthToMatchingParen(Current, State.Stack);
@@ -1279,6 +1294,9 @@ unsigned ContinuationIndenter::getNewLineColumn(const LineState &State) {
FormatToken &Current = *State.NextToken;
const auto &CurrentState = State.Stack.back();
+ if (Current.ClosesTemplateDeclaration && Style.BreakBeforeTemplateClose)
+ return CurrentState.Indent - Style.ContinuationIndentWidth;
+
if (CurrentState.IsCSharpGenericTypeConstraint &&
Current.isNot(TT_CSharpGenericTypeConstraint)) {
return CurrentState.ColonPos + 2;
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index ee52972ce66f4a..d6aa80dd8e3aef 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -1000,6 +1000,7 @@ template <> struct MappingTraits<FormatStyle> {
IO.mapOptional("BreakBeforeBraces", Style.BreakBeforeBraces);
IO.mapOptional("BreakBeforeInlineASMColon",
Style.BreakBeforeInlineASMColon);
+ IO.mapOptional("BreakBeforeTemplateClose", Style.BreakBeforeTemplateClose);
IO.mapOptional("BreakBeforeTernaryOperators",
Style.BreakBeforeTernaryOperators);
IO.mapOptional("BreakBinaryOperations", Style.BreakBinaryOperations);
@@ -1514,6 +1515,7 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
LLVMStyle.BreakBeforeBraces = FormatStyle::BS_Attach;
LLVMStyle.BreakBeforeConceptDeclarations = FormatStyle::BBCDS_Always;
LLVMStyle.BreakBeforeInlineASMColon = FormatStyle::BBIAS_OnlyMultiline;
+ LLVMStyle.BreakBeforeTemplateClose = false;
LLVMStyle.BreakBeforeTernaryOperators = true;
LLVMStyle.BreakBinaryOperations = FormatStyle::BBO_Never;
LLVMStyle.BreakConstructorInitializers = FormatStyle::BCIS_BeforeColon;
diff --git a/clang/unittests/Format/ConfigParseTest.cpp b/clang/unittests/Format/ConfigParseTest.cpp
index 7fc7492271668b..39f4ea49719600 100644
--- a/clang/unittests/Format/ConfigParseTest.cpp
+++ b/clang/unittests/Format/ConfigParseTest.cpp
@@ -162,6 +162,7 @@ TEST(ConfigParseTest, ParsesConfigurationBools) {
CHECK_PARSE_BOOL(BinPackArguments);
CHECK_PARSE_BOOL(BreakAdjacentStringLiterals);
CHECK_PARSE_BOOL(BreakAfterJavaFieldAnnotations);
+ CHECK_PARSE_BOOL(BreakBeforeTemplateClose);
CHECK_PARSE_BOOL(BreakBeforeTernaryOperators);
CHECK_PARSE_BOOL(BreakStringLiterals);
CHECK_PARSE_BOOL(CompactNamespaces);
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 250e51b5421664..1dffce7925a055 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -11077,6 +11077,85 @@ TEST_F(FormatTest, WrapsTemplateDeclarationsWithComments) {
Style);
}
+TEST_F(FormatTest, BreakBeforeTemplateClose) {
+ FormatStyle Style = getGoogleStyle(FormatStyle::LK_Cpp);
+ Style.BreakTemplateDeclarations = FormatStyle::BTDS_Yes;
+ Style.ColumnLimit = 0;
+ verifyNoChange("template <typename Foo>\n"
+ "void foo() {}",
+ Style);
+ verifyNoChange("template <\n"
+ " typename Foo,\n"
+ " typename Bar>\n"
+ "void foo() {}",
+ Style);
+ // when BreakBeforeTemplateClose is off, this line break is removed:
+ verifyFormat("template <\n"
+ " typename Foo,\n"
+ " typename Bar>\n"
+ "void foo() {}",
+ "template <\n"
+ " typename Foo,\n"
+ " typename Bar\n"
+ ">\n"
+ "void foo() {}",
+ Style);
+ Style.BreakBeforeTemplateClose = true;
+ // BreakBeforeTemplateClose should NOT force multiline templates
+ verifyNoChange("template <typename Foo>\n"
+ "void foo() {}",
+ Style);
+ verifyNoChange("template <typename Foo, typename Bar>\n"
+ "void foo() {}",
+ Style);
+ // it should allow a line break:
+ verifyNoChange("template <\n"
+ " typename Foo\n"
+ ">\n"
+ "void foo() {}",
+ Style);
+ verifyNoChange("template <\n"
+ " typename Foo,\n"
+ " typename Bar\n"
+ ">\n"
+ "void foo() {}",
+ Style);
+ // it should add a line break if not already present:
+ verifyFormat("template <\n"
+ " typename Foo\n"
+ ">\n"
+ "void foo() {}",
+ "template <\n"
+ " typename Foo>\n"
+ "void foo() {}",
+ Style);
+ verifyFormat("template <\n"
+ " typename Foo,\n"
+ " typename Bar\n"
+ ">\n"
+ "void foo() {}",
+ "template <\n"
+ " typename Foo,\n"
+ " typename Bar>\n"
+ "void foo() {}",
+ Style);
+ // when within an indent scope, the > should be placed appropriately:
+ verifyFormat("struct Baz {\n"
+ " template <\n"
+ " typename Foo,\n"
+ " typename Bar\n"
+ " >\n"
+ " void foo() {}\n"
+ "};",
+ "struct Baz {\n"
+ " template <\n"
+ " typename Foo,\n"
+ " typename Bar>\n"
+ " void foo() {}\n"
+ "};",
+ Style);
+}
+
TEST_F(FormatTest, WrapsTemplateParameters) {
FormatStyle Style = getLLVMStyle();
Style.AlignAfterOpenBracket = FormatStyle::BAS_DontAlign;
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Ping 🙏 |
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Would this also be equivalent to supporting |
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Yes. I followed the code that implements |
Maybe we should make it a sub-option for |
I thought about it some more and I don't think it would be a good idea. Having a separate option seems a bit easier to handle, and allows mixing and matching by users. |
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I think you should add test cases with multiple Consider trying the code snippet mentioned in #80049 as well. |
Thank you for the suggestion! I have integrated that test case. It indicated that I was being too narrow - |
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Ping 🙏 |
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Thank you so much for taking the time to review the tests! I apologize for all the redundancies. I believe I have addressed all of your comments here: leijurv@e1eaba9 |
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GitHub is having issues it appears - the commit leijurv@e1eaba9 is certainly pushed, and I even tried pushing an empty commit on top to kick github into working, leijurv@7d456ca but still this PR is in a glitched state that doesn't show those commits... 
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Ah, it resolved itself as of leijurv@b6219e2 |
owenca
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Co-authored-by: Owen Pan <[email protected]>
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@leijurv Congratulations on having your first Pull Request (PR) merged into the LLVM Project! Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR. Please check whether problems have been caused by your change specifically, as the builds can include changes from many authors. It is not uncommon for your change to be included in a build that fails due to someone else's changes, or infrastructure issues. How to do this, and the rest of the post-merge process, is covered in detail here. If your change does cause a problem, it may be reverted, or you can revert it yourself. This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again. If you don't get any reports, no action is required from you. Your changes are working as expected, well done! |
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Can this option be used to format any template like std::remove_cv_t<add_common_cv_reference<std::common_type_t<std::decay_t, std::decay_t>,T0,T1>>;? |
Yes! In fact, that exact case is tested. d2b45ce#diff-3f6f57cda9809a57c5b79e22b4181b3f3aaac7216262d0ef44108f39b0443e9bR11276-R11290 // Test from https://github.com/llvm/llvm-project/issues/80049:
verifyFormat(
"using type = std::remove_cv_t<\n"
" add_common_cv_reference<\n"
" std::common_type_t<std::decay_t<T0>, std::decay_t<T1>>,\n"
" T0,\n"
" T1\n"
" >\n"
">;",
"using type = std::remove_cv_t<\n"
" add_common_cv_reference<\n"
" std::common_type_t<std::decay_t<T0>, std::decay_t<T1>>,\n"
" T0,\n"
" T1>>;",
Style); |
In clang-format, multiline templates have the `>` on the same line as
the last parameter:
```c++
template <
typename Foo,
typename Bar>
void foo() {
```
I would like to add an option to put the `>` on the next line, like
this:
```c++
template <
typename Foo,
typename Bar
>
void foo() {
```
An example of a large project that uses this style is NVIDIA's CUTLASS,
here is an example:
https://github.com/NVIDIA/cutlass/blob/main/include/cutlass/epilogue/dispatch_policy.hpp#L149-L156
My reasoning is that it reminds me of this style of braces:
```c++
if (foo()) {
bar();
baz();}
```
Most people agree this is better:
```c++
if (foo()) {
bar();
baz();
}
```
---------
Co-authored-by: Owen Pan <[email protected]>
In clang-format, multiline templates have the
>on the same line as the last parameter:I would like to add an option to put the
>on the next line, like this:An example of a large project that uses this style is NVIDIA's CUTLASS, here is an example:
https://github.com/NVIDIA/cutlass/blob/main/include/cutlass/epilogue/dispatch_policy.hpp#L149-L156
My reasoning is that it reminds me of this style of braces:
Most people agree this is better: