clang-format: Preserve meaning of trailing comments on parameters.

Formatting:
  SomeFunction(a,
            b, // comment
            c);

Before:
  SomeFunction(a, b, // comment
               c);

After:
  SomeFunction(a,
               b, // comment
               c);

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204456 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Format/TokenAnnotator.cpp b/lib/Format/TokenAnnotator.cpp
index a91c847452155356e8aa0080e804f8595aca93e8..08f2b27ed580ba80cf4fe25eef8c2a14dc7ef654 100644 (file)
--- a/lib/Format/TokenAnnotator.cpp
+++ b/lib/Format/TokenAnnotator.cpp
@@ -1114,6 +1114,27 @@ void TokenAnnotator::calculateFormattingInformation(AnnotatedLine &Line) {
         Current->SpacesRequiredBefore = Style.Cpp11BracedListStyle ? 0 : 1;
       else
         Current->SpacesRequiredBefore = Style.SpacesBeforeTrailingComments;
+
+      // If we find a trailing comment, iterate backwards to determine whether
+      // it seems to relate to a specific parameter. If so, break before that
+      // parameter to avoid changing the comment's meaning. E.g. don't move 'b'
+      // to the previous line in:
+      //   SomeFunction(a,
+      //                b, // comment
+      //                c);
+      if (Current->isTrailingComment()) {
+        for (FormatToken *Parameter = Current->Previous; Parameter;
+             Parameter = Parameter->Previous) {
+          if (Parameter->isOneOf(tok::comment, tok::r_brace))
+            break;
+          if (Parameter->Previous && Parameter->Previous->is(tok::comma)) {
+            if (Parameter->Previous->Type != TT_CtorInitializerComma &&
+                Parameter->HasUnescapedNewline)
+              Parameter->MustBreakBefore = true;
+            break;
+          }
+        }
+      }
     } else if (Current->SpacesRequiredBefore == 0 &&
              spaceRequiredBefore(Line, *Current)) {
       Current->SpacesRequiredBefore = 1;

diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index 282a4432472841cfeed290f74986f44bb39150cd..537a01f954f7ca1dbbea8751daa1206d59d5307d 100644 (file)
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -777,6 +777,25 @@ TEST_F(FormatTest, UnderstandsSingleLineComments) {
                    "otherLine();"));
 }
 
+TEST_F(FormatTest, KeepsParameterWithTrailingCommentsOnTheirOwnLine) {
+  EXPECT_EQ("SomeFunction(a,\n"
+            "             b, // comment\n"
+            "             c);",
+            format("SomeFunction(a,\n"
+                   "          b, // comment\n"
+                   "      c);"));
+  EXPECT_EQ("SomeFunction(a, b, // comment (unclear relation)\n"
+            "             c);",
+            format("SomeFunction(a, b, // comment (unclear relation)\n"
+                   "      c);"));
+  EXPECT_EQ("SomeFunction(a, // comment\n"
+            "             b,\n"
+            "             c); // comment",
+            format("SomeFunction(a,     // comment\n"
+                   "          b,\n"
+                   "      c); // comment"));
+}
+
 TEST_F(FormatTest, CanFormatCommentsLocally) {
   EXPECT_EQ("int a;    // comment\n"
             "int    b; // comment",