clang-format: merge short case labels with trailing comments

[Typz]

Summary

Allow merging short case labels when they actually end with a comment
(like a comment after the `break`) and when followed by switch-level
comments (e.g. aligned with next case):

switch(a) {
case 0: break; // comment at end of case
case 1: return value;
// comment related to next case
// comment related to next case
case 2:
}

[krasimir]

lib/Format/UnwrappedLineFormatter.cpp

405

I'd change J[0] to *J and rename Line to something else so that it doesn't shadow Line.

406

Please add a test for this if.

unittests/Format/FormatTest.cpp

912

I'd suggest adding more cases here, like:

"case 6: /* comment */ x = 1; break;\n"
"case 7: x = /* comment */ 1; break;\n"
"case 8:\n"
"  x = 1; /* comment */\n"
"  break;\n"
"case 9:\n"
"  break; // comment line 1\n"
"         // comment line 2\n"
"case 10:\n"
"  return; /* comment line 1\n"
"           * comment line 2 */\n"
"}",

I'm interested also why case 10 here fails.

930

I'd like to see tests where an overly long comment line appears, like:

EXPECT_EQ("switch (a) {\n"
          "case 0:\n"
          "  return; // long long long long long long long long long long "
          "long long comment\n"
          "          // line\n"
          "}",
          format("switch (a) {\n"
                 "case 0: return; // long long long long long long long "
                 "long long long long long comment line\n"
                 "}",
                 Style));
EXPECT_EQ("switch (a) {\n"
          "case 0:\n"
          "  return; /* long long long long long long long long long long "
          "long long comment\n"
          "             line */\n"
          "}",
          format("switch (a) {\n"
                 "case 0: return; /* long long long long long long long "
                 "long long long long long comment line */\n"
                 "}",
                 Style));

[Typz]

Address review comments

unittests/Format/FormatTest.cpp

912

case 10 fails because of test::messUp(), which removes the line break inside the comment.

[krasimir]

Looks good! Thanks!

lib/Format/UnwrappedLineFormatter.cpp

private:
   tryMergeShortCaseLabels(SmallVectorImpl<AnnotatedLine *>::const_iterator I,
                           SmallVectorImpl<AnnotatedLine *>::const_iterator E,
                           unsigned Limit) {
     if (Limit == 0 || I + 1 == E ||
         I[1]->First->isOneOf(tok::kw_case, tok::kw_default))
       return 0;
     unsigned NumStmts = 0;
     unsigned Length = 0;
+    bool EndsWithComment = false;
     bool InPPDirective = I[0]->InPPDirective;
+    const unsigned Level = I[0]->Level;
     for (; NumStmts < 3; ++NumStmts) {
       if (I + 1 + NumStmts == E)
         break;
       const AnnotatedLine *Line = I[1 + NumStmts];
       if (Line->InPPDirective != InPPDirective)
         break;
       if (Line->First->isOneOf(tok::kw_case, tok::kw_default, tok::r_brace))
         break;
       if (Line->First->isOneOf(tok::kw_if, tok::kw_for, tok::kw_switch,
-                               tok::kw_while, tok::comment) ||
-          Line->Last->is(tok::comment))
+                               tok::kw_while) ||
+          EndsWithComment)
         return 0;
+      if (Line->First->is(tok::comment)) {
+        if (Level != Line->Level)
+          return 0;
+        SmallVectorImpl<AnnotatedLine *>::const_iterator J = I + 2 + NumStmts;
+        for (; J != E; ++J) {
+          const AnnotatedLine *Line = J[0];
+          if (Line->InPPDirective != InPPDirective)
+            break;
+          if (Line->First->isOneOf(tok::kw_case, tok::kw_default, tok::r_brace))
+            break;
+          if (Line->First->isNot(tok::comment) || Level != Line->Level)
+            return 0;
+        }
+        break;
+      }
+      if (Line->Last->is(tok::comment))
+        EndsWithComment = true;
       Length += I[1 + NumStmts]->Last->TotalLength + 1; // 1 for the space.
     }
     if (NumStmts == 0 || NumStmts == 3 || Length > Limit)
       return 0;
     return NumStmts;
   }
 
   unsigned

unittests/Format/FormatTest.cpp

verifyFormat("switch (a) {\n"
                "  return;\n"
                "case 8:\n"
                "  x = 8; // comment\n"
                "  break;\n"
                "default: y = 1; break;\n"
                "}",
                Style);
   verifyFormat("switch (a) {\n"
+               "case 0: return; // comment\n"
+               "case 1: break;  // comment\n"
+               "case 2: return;\n"
+               "// comment\n"
+               "case 3: return;\n"
+               "// comment 1\n"
+               "// comment 2\n"
+               "// comment 3\n"
+               "case 4: break; /* comment */\n"
+               "case 5:\n"
+               "  // comment\n"
+               "  break;\n"
+               "}",
+               Style);
+  EXPECT_EQ("switch (a) {\n"
+            "case 1:\n"
+            "  x = 8;\n"
+            "  // fall through\n"
+            "case 2: x = 8;\n"
+            "// comment\n"
+            "default:\n"
+            "}",
+            format("switch (a) {\n"
+                   "case 1: x = 8;\n"
+                   "  // fall through\n"
+                   "case 2:\n"
+                   "  x = 8;\n"
+                   "// comment\n"
+                   "default:\n"
+                   "}",
+                   Style));
+  verifyFormat("switch (a) {\n"
                "#if FOO\n"
                "case 0: return 0;\n"
                "#endif\n"
                "}",
                Style);
   verifyFormat("switch (a) {\n"
                "case 1: {\n"
                "}\n"