[clang-format] Fix a bug in BWACS_MultiLine

Fix #51940

Author: owenca

clang/lib/Format/TokenAnnotator.cpp

@@ -4153,8 +4153,16 @@ void TokenAnnotator::calculateFormattingInformation(AnnotatedLine &Line) const {
                              ChildSize + Current->SpacesRequiredBefore;
     }
 
-    if (Current->is(TT_CtorInitializerColon))
+    if (Current->is(TT_ControlStatementLBrace) && Style.ColumnLimit > 0 &&
+        Style.BraceWrapping.AfterControlStatement ==
+            FormatStyle::BWACS_MultiLine &&
+        Line.Level * Style.IndentWidth + Line.Last->TotalLength >
+            Style.ColumnLimit) {
+      Current->CanBreakBefore = true;
+      Current->MustBreakBefore = true;
+    } else if (Current->is(TT_CtorInitializerColon)) {
       InFunctionDecl = false;
+    }
 
     // FIXME: Only calculate this if CanBreakBefore is true once static
     // initializers etc. are sorted out.
@@ -5586,12 +5594,13 @@ static bool isAllmanLambdaBrace(const FormatToken &Tok) {
 
 bool TokenAnnotator::mustBreakBefore(const AnnotatedLine &Line,
                                      const FormatToken &Right) const {
-  const FormatToken &Left = *Right.Previous;
   if (Right.NewlinesBefore > 1 && Style.MaxEmptyLinesToKeep > 0 &&
       (!Style.RemoveEmptyLinesInUnwrappedLines || &Right == Line.First)) {
     return true;
   }
 
+  const FormatToken &Left = *Right.Previous;
+
   if (Style.BreakFunctionDefinitionParameters && Line.MightBeFunctionDecl &&
       Line.mightBeFunctionDefinition() && Left.MightBeFunctionDeclParen &&
       Left.ParameterCount > 0) {

clang/lib/Format/UnwrappedLineFormatter.cpp

@@ -424,43 +424,14 @@ class LineJoiner {
                  : 0;
     }
     // Try to merge a control statement block with left brace wrapped.
-    if (NextLine.First->is(tok::l_brace)) {
-      if ((TheLine->First->isOneOf(tok::kw_if, tok::kw_else, tok::kw_while,
-                                   tok::kw_for, tok::kw_switch, tok::kw_try,
-                                   tok::kw_do, TT_ForEachMacro) ||
-           (TheLine->First->is(tok::r_brace) && TheLine->First->Next &&
-            TheLine->First->Next->isOneOf(tok::kw_else, tok::kw_catch))) &&
-          Style.BraceWrapping.AfterControlStatement ==
-              FormatStyle::BWACS_MultiLine) {
-        // If possible, merge the next line's wrapped left brace with the
-        // current line. Otherwise, leave it on the next line, as this is a
-        // multi-line control statement.
-        return (Style.ColumnLimit == 0 || TheLine->Level * Style.IndentWidth +
-                                                  TheLine->Last->TotalLength <=
-                                              Style.ColumnLimit)
-                   ? 1
-                   : 0;
-      }
-      if (TheLine->First->isOneOf(tok::kw_if, tok::kw_else, tok::kw_while,
-                                  tok::kw_for, TT_ForEachMacro)) {
-        return (Style.BraceWrapping.AfterControlStatement ==
-                FormatStyle::BWACS_Always)
-                   ? tryMergeSimpleBlock(I, E, Limit)
-                   : 0;
-      }
-      if (TheLine->First->isOneOf(tok::kw_else, tok::kw_catch) &&
-          Style.BraceWrapping.AfterControlStatement ==
-              FormatStyle::BWACS_MultiLine) {
-        // This case if different from the upper BWACS_MultiLine processing
-        // in that a preceding r_brace is not on the same line as else/catch
-        // most likely because of BeforeElse/BeforeCatch set to true.
-        // If the line length doesn't fit ColumnLimit, leave l_brace on the
-        // next line to respect the BWACS_MultiLine.
-        return (Style.ColumnLimit == 0 ||
-                TheLine->Last->TotalLength <= Style.ColumnLimit)
-                   ? 1
-                   : 0;
-      }
+    if (NextLine.First->is(TT_ControlStatementLBrace)) {
+      // If possible, merge the next line's wrapped left brace with the
+      // current line. Otherwise, leave it on the next line, as this is a
+      // multi-line control statement.
+      return Style.BraceWrapping.AfterControlStatement ==
+                     FormatStyle::BWACS_Always
+                 ? tryMergeSimpleBlock(I, E, Limit)
+                 : 0;
     }
     if (PreviousLine && TheLine->First->is(tok::l_brace)) {
       switch (PreviousLine->First->Tok.getKind()) {

clang/lib/Format/UnwrappedLineParser.cpp

@@ -135,7 +135,8 @@ class CompoundStatementIndenter {
   CompoundStatementIndenter(UnwrappedLineParser *Parser,
                             const FormatStyle &Style, unsigned &LineLevel)
       : CompoundStatementIndenter(Parser, LineLevel,
-                                  Style.BraceWrapping.AfterControlStatement,
+                                  Style.BraceWrapping.AfterControlStatement ==
+                                      FormatStyle::BWACS_Always,
                                   Style.BraceWrapping.IndentBraces) {}
   CompoundStatementIndenter(UnwrappedLineParser *Parser, unsigned &LineLevel,
                             bool WrapBrace, bool IndentBrace)
@@ -3067,7 +3068,7 @@ void UnwrappedLineParser::parseTryCatch() {
     parseStructuralElement();
     --Line->Level;
   }
-  while (true) {
+  for (bool SeenCatch = false;;) {
     if (FormatTok->is(tok::at))
       nextToken();
     if (!(FormatTok->isOneOf(tok::kw_catch, Keywords.kw___except,
@@ -3090,6 +3091,10 @@ void UnwrappedLineParser::parseTryCatch() {
       }
       nextToken();
     }
+    if (SeenCatch) {
+      FormatTok->setFinalizedType(TT_ControlStatementLBrace);
+      SeenCatch = false;
+    }
     NeedsUnwrappedLine = false;
     Line->MustBeDeclaration = false;
     CompoundStatementIndenter Indenter(this, Style, Line->Level);

clang/unittests/Format/FormatTest.cpp

@@ -3419,6 +3419,17 @@ TEST_F(FormatTest, MultiLineControlStatements) {
                "{\n"
                "};",
                Style);
+
+  Style = getLLVMStyle();
+  Style.AllowShortBlocksOnASingleLine = FormatStyle::SBS_Always;
+  Style.AllowShortIfStatementsOnASingleLine = FormatStyle::SIS_WithoutElse;
+  Style.AllowShortLoopsOnASingleLine = true;
+  Style.BreakBeforeBraces = FormatStyle::BS_Custom;
+  Style.BraceWrapping.AfterControlStatement = FormatStyle::BWACS_MultiLine;
+  verifyFormat("if (true) { return; }", Style);
+  verifyFormat("while (true) { return; }", Style);
+  // Failing test in https://reviews.llvm.org/D114521#3151727
+  verifyFormat("for (;;) { bar(); }", Style);
 }
 
 TEST_F(FormatTest, BeforeWhile) {