1 files changed, 44 insertions, 16 deletions

diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index 778ffe30f62..7f1ac848f4f 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -20,7 +20,7 @@
 #include "clang/Format/Format.h"
 #include "llvm/Support/Debug.h"
 
-#define DEBUG_TYPE "format-formatter"
+#define DEBUG_TYPE "format-indenter"
 
 namespace clang {
 namespace format {
@@ -1154,7 +1154,11 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
     }
   } else if (Current.is(TT_BlockComment)) {
     if (!Current.isTrailingComment() || !Style.ReflowComments ||
-        CommentPragmasRegex.match(Current.TokenText.substr(2)))
+        CommentPragmasRegex.match(Current.TokenText.substr(2)) ||
+        // If a comment token switches formatting, like
+        // /* clang-format on */, we don't want to break it further,
+        // but we may still want to adjust its indentation.
+        switchesFormatting(Current))
       return addMultilineToken(Current, State);
     Token.reset(new BreakableBlockComment(
         Current, State.Line->Level, StartColumn, Current.OriginalColumn,
@@ -1163,11 +1167,13 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
              (Current.Previous == nullptr ||
               Current.Previous->isNot(TT_ImplicitStringLiteral))) {
     if (!Style.ReflowComments ||
-        CommentPragmasRegex.match(Current.TokenText.substr(2)))
+        CommentPragmasRegex.match(Current.TokenText.substr(2)) ||
+        switchesFormatting(Current))
       return 0;
-    Token.reset(new BreakableLineComment(Current, State.Line->Level,
-                                         StartColumn, /*InPPDirective=*/false,
-                                         Encoding, Style));
+    Token.reset(new BreakableLineCommentSection(
+        Current, State.Line->Level, StartColumn, Current.OriginalColumn,
+        !Current.Previous,
+        /*InPPDirective=*/false, Encoding, Style));
     // We don't insert backslashes when breaking line comments.
     ColumnLimit = Style.ColumnLimit;
   } else {
@@ -1178,15 +1184,27 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
 
   unsigned RemainingSpace = ColumnLimit - Current.UnbreakableTailLength;
   bool BreakInserted = false;
+  // We use a conservative reflowing strategy. Reflow starts after a line is
+  // broken or the corresponding whitespace compressed. Reflow ends as soon as a
+  // line that doesn't get reflown with the previous line is reached.
+  bool ReflowInProgress = false;
   unsigned Penalty = 0;
   unsigned RemainingTokenColumns = 0;
   for (unsigned LineIndex = 0, EndIndex = Token->getLineCount();
        LineIndex != EndIndex; ++LineIndex) {
+    BreakableToken::Split SplitBefore(StringRef::npos, 0);
+    if (ReflowInProgress) {
+      SplitBefore = Token->getSplitBefore(LineIndex, RemainingTokenColumns,
+                                          RemainingSpace);
+    }
+    ReflowInProgress = SplitBefore.first != StringRef::npos;
+    unsigned TailOffset =
+        ReflowInProgress ? (SplitBefore.first + SplitBefore.second) : 0;
     if (!DryRun)
-      Token->replaceWhitespaceBefore(LineIndex, Whitespaces);
-    unsigned TailOffset = 0;
-    RemainingTokenColumns =
-        Token->getLineLengthAfterSplit(LineIndex, TailOffset, StringRef::npos);
+      Token->replaceWhitespaceBefore(LineIndex, RemainingTokenColumns,
+                                     RemainingSpace, SplitBefore, Whitespaces);
+    RemainingTokenColumns = Token->getLineLengthAfterSplitBefore(
+        LineIndex, TailOffset, RemainingTokenColumns, ColumnLimit, SplitBefore);
     while (RemainingTokenColumns > RemainingSpace) {
       BreakableToken::Split Split =
           Token->getSplit(LineIndex, TailOffset, ColumnLimit);
@@ -1198,17 +1216,23 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
         break;
       }
       assert(Split.first != 0);
-      unsigned NewRemainingTokenColumns = Token->getLineLengthAfterSplit(
-          LineIndex, TailOffset + Split.first + Split.second, StringRef::npos);
 
-      // We can remove extra whitespace instead of breaking the line.
-      if (RemainingTokenColumns + 1 - Split.second <= RemainingSpace) {
-        RemainingTokenColumns = 0;
+      // Check if compressing the whitespace range will bring the line length
+      // under the limit. If that is the case, we perform whitespace compression
+      // instead of inserting a line break.
+      unsigned RemainingTokenColumnsAfterCompression =
+          Token->getLineLengthAfterCompression(RemainingTokenColumns, Split);
+      if (RemainingTokenColumnsAfterCompression <= RemainingSpace) {
+        RemainingTokenColumns = RemainingTokenColumnsAfterCompression;
+        ReflowInProgress = true;
         if (!DryRun)
-          Token->replaceWhitespace(LineIndex, TailOffset, Split, Whitespaces);
+          Token->compressWhitespace(LineIndex, TailOffset, Split, Whitespaces);
         break;
       }
 
+      unsigned NewRemainingTokenColumns = Token->getLineLengthAfterSplit(
+          LineIndex, TailOffset + Split.first + Split.second, StringRef::npos);
+
       // When breaking before a tab character, it may be moved by a few columns,
       // but will still be expanded to the next tab stop, so we don't save any
       // columns.
@@ -1226,6 +1250,7 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
       }
       TailOffset += Split.first + Split.second;
       RemainingTokenColumns = NewRemainingTokenColumns;
+      ReflowInProgress = true;
       BreakInserted = true;
     }
   }
@@ -1246,6 +1271,9 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
 
     State.Stack.back().LastSpace = StartColumn;
   }
+
+  Token->updateNextToken(State);
+
   return Penalty;
 }