[clang-format] Allow short function body on a single line

[brandb97]

Fix #145161

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-format

Author: Lidong Yan (brandb97)

Changes

Fix issue #145161

---

Full diff: https://github.com/llvm/llvm-project/pull/151428.diff

4 Files Affected:

• (modified) clang/include/clang/Format/Format.h (+6)
• (modified) clang/lib/Format/Format.cpp (+3)
• (modified) clang/lib/Format/UnwrappedLineFormatter.cpp (+20)
• (modified) clang/lib/Format/UnwrappedLineParser.cpp (+4)

diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
index 31582a40de866..e13df9df83e18 100644
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -878,6 +878,12 @@ struct FormatStyle {
   /// \version 3.5
   ShortFunctionStyle AllowShortFunctionsOnASingleLine;
 
+  /// Dependent on the value, function body like ``{ return 0; }`` can be
+  /// put on a single line. Only when AllowShortFunctionsOnASingleLine = None
+  /// and AllowShortBlocksOnASingleLine != Never, the value of this option
+  /// is true.
+  bool AllowShortFunctionBodiesOnASingleLine;
+
   /// Different styles for handling short if statements.
   enum ShortIfStyle : int8_t {
     /// Never put short ifs on the same line.
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index 063780721423f..61c0d399ca796 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -3828,6 +3828,9 @@ reformat(const FormatStyle &Style, StringRef Code,
   default:
     break;
   }
+  Expanded.AllowShortFunctionBodiesOnASingleLine =
+      Expanded.AllowShortFunctionsOnASingleLine == FormatStyle::SFS_None &&
+      Expanded.AllowShortBlocksOnASingleLine != FormatStyle::SBS_Never;
 
   if (Expanded.DisableFormat)
     return {tooling::Replacements(), 0};
diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 0adf7ee9ed543..44c767a0db9b8 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -257,6 +257,12 @@ class LineJoiner {
       return tryMergeSimpleBlock(I, E, Limit);
     }
 
+    if (TheLine->Last->is(TT_FunctionLBrace) &&
+        TheLine->First == TheLine->Last &&
+        Style.AllowShortFunctionBodiesOnASingleLine) {
+      return tryMergeSimpleBlock(I, E, Limit);
+    }
+
     const auto *PreviousLine = I != AnnotatedLines.begin() ? I[-1] : nullptr;
     // Handle empty record blocks where the brace has already been wrapped.
     if (PreviousLine && TheLine->Last->is(tok::l_brace) &&
@@ -532,6 +538,20 @@ class LineJoiner {
       }
       return MergedLines;
     }
+
+    // Previously, UnwrappedLineParser would move the left brace to a new line
+    // when AllowShortFunctionBodiesOnASingleLine is enabled. However, if the
+    // function body cannot fit on a single line, and Style.BraceWrapping.AfterFunction
+    // is false, we should merge the function name and the left brace back onto
+    // the same line
+    if (NextLine.First->is(TT_FunctionLBrace) &&
+        Style.AllowShortFunctionBodiesOnASingleLine &&
+        !Style.BraceWrapping.AfterFunction) {
+      unsigned MergedLines = 0;
+      MergedLines = tryMergeSimpleBlock(I + 1, E, Limit);
+      return MergedLines > 0 ? 0 : 1;
+    }
+
     auto IsElseLine = [&TheLine]() -> bool {
       const FormatToken *First = TheLine->First;
       if (First->is(tok::kw_else))
diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 91b8fdc8a3c38..7dd59c1cbd678 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1921,6 +1921,10 @@ void UnwrappedLineParser::parseStructuralElement(
           }
         } else if (Style.BraceWrapping.AfterFunction) {
           addUnwrappedLine();
+        } else if (Style.AllowShortFunctionBodiesOnASingleLine) {
+          // Wrap the left brace here; we'll try to merge it back
+          // later if needed.
+          addUnwrappedLine();
         }
         if (!Previous || Previous->isNot(TT_TypeDeclarationParen))
           FormatTok->setFinalizedType(TT_FunctionLBrace);

[github-actions]

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

[HazardyKnusperkeks]

You are missing unit tests. clang/unittests/Format/FromatTest.cpp.

[brandb97]

ping

[owenca]

Can we fix the bug instead of adding an option?

[brandb97]

Sorry, I promised to add enum PutShortFunctionBodiesOnASingleLine option, but I haven’t touched this code in quite a while (due to summer vacation). It seems the requirements have changed since then, so maybe it was a good thing I didn’t write it after all? ;-)

[brandb97]

I can just fix the bug by moving PutShortFunctionBodiesOnASingleLine to private area in FormatStyle and set PutShortFunctionBodiesOnASingleLine to Always if and only if AllowShortFunctionsOnASingleLine is Never and AllowShortBlocksOnASingleLine is Always. Is that what I should do?

[brandb97]

@owenca I actually think adding a new option would be better. The reason is that when users want to specify putting function bodies on a single line, without a new option, they would have to set
AllowShortFunctionsOnASingleLine: Never
AllowShortBlocksOnASingleLine: Always
But such a setting would also cause shorter if and while blocks to be placed on a single line, which users might not want. With a new option, this problem wouldn’t occur.

[owenca]

Sorry, I promised to add enum PutShortFunctionBodiesOnASingleLine option, but I haven’t touched this code in quite a while (due to summer vacation). It seems the requirements have changed since then, so maybe it was a good thing I didn’t write it after all? ;-)

I don't think the requirements have changed from my perspective. See #145161 (comment).

@owenca I actually think adding a new option would be better. The reason is that when users want to specify putting function bodies on a single line, without a new option, they would have to set AllowShortFunctionsOnASingleLine: Never AllowShortBlocksOnASingleLine: Always But such a setting would also cause shorter if and while blocks to be placed on a single line, which users might not want. With a new option, this problem wouldn’t occur.

We can't keep adding all kinds of options people can come up with. See https://clang.llvm.org/docs/ClangFormatStyleOptions.html#adding-additional-style-options.

[brandb97]

I see, I’ll rewrite this part of the code.

[brandb97]

@owenca Could you help review my code? Thank you very much.

[owenca]

See #145161 (comment). Sorry about that! Hopefully this requirement change makes the fix much simpler.

[brandb97]

@owenca That's totally fine, I will try to simplify my code.

[brandb97]

owenca ***@***.***> writes:

@owenca commented on this pull request. In clang/unittests/Format/FormatTest.cpp: > +TEST_F(FormatTest, SplitShortFunction) { + FormatStyle Style = getLLVMStyleWithColumns(40); We've been consistently using auto in place of FormatStyle and other types for a few years now. Also, there's no need for ColumnLimit: 40 here now.

Understand, I will just remove them. Thanks, Lidong