[PATCH] D36614: [clang-format] Refine trailing comment detection

[Krasimir Georgiev via Phabricator via cfe-commits]

krasimir created this revision.
Herald added a subscriber: klimek.

This patch fixes an non-idempotency issue connected with detection of trailing
comments. Consider formatting the following code with column limit at `V`:

                      V
  const /* comment comment */ A = B;

The comment is not a trailing comment, breaking before it doesn't bring it under
the column limit. The formatter breaks after it, resulting in:

                      V
  const /* comment comment */
      A = B;

For a next reformat, the formatter considers the comment as a trailing comment,
so it is free to break it further, resulting in:

                      V
  const /* comment
           comment */
      A = B;

This patch improves this by refining the trailing comment detection, so that
the comment in the second version is not considered trailing anymore.


https://reviews.llvm.org/D36614

Files:
  lib/Format/FormatToken.h
  unittests/Format/FormatTestComments.cpp


Index: unittests/Format/FormatTestComments.cpp
===================================================================
--- unittests/Format/FormatTestComments.cpp
+++ unittests/Format/FormatTestComments.cpp
@@ -451,6 +451,17 @@
   verifyFormat("f(/* aaaaaaaaaaaaaaaaaa = */\n"
                "  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa);");
 
+  verifyFormat("const /** comment comment */ A = B;",
+               getLLVMStyleWithColumns(40));
+
+  verifyFormat("const /** comment comment comment */ A =\n"
+               "    B;",
+               getLLVMStyleWithColumns(40));
+
+  verifyFormat("const /** comment comment comment comment */\n"
+               "    A = B;",
+               getLLVMStyleWithColumns(40));
+
   FormatStyle NoBinPacking = getLLVMStyle();
   NoBinPacking.BinPackParameters = false;
   verifyFormat("aaaaaaaa(/* parameter 1 */ aaaaaa,\n"
Index: lib/Format/FormatToken.h
===================================================================
--- lib/Format/FormatToken.h
+++ lib/Format/FormatToken.h
@@ -391,7 +391,11 @@
 
   bool isTrailingComment() const {
     return is(tok::comment) &&
-           (is(TT_LineComment) || !Next || Next->NewlinesBefore > 0);
+           (is(TT_LineComment) || !Next ||
+            (Next->NewlinesBefore > 0 &&
+             (!Previous ||
+              Previous->isOneOf(tok::comma, tok::equal, tok::l_brace) ||
+              Next->is(tok::r_brace))));
   }
 
   /// \brief Returns \c true if this is a keyword that can be used


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