clang-format: merge short case labels with trailing comments

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:
  }

Reviewers: krasimir, djasper

Reviewed By: krasimir

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D35557

llvm-svn: 309370

2 files changed, 92 insertions, 2 deletions

diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
index 2005a282292..09e732edae6 100644
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -382,7 +382,9 @@ private:
       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;
@@ -392,9 +394,26 @@ private:
       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) {
+          Line = *J;
+          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)
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index f533ebf2234..4577a67fd13 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -907,6 +907,77 @@ TEST_F(FormatTest, ShortCaseLabels) {
                "}",
                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"
+               "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"
+               "}",
+               Style);
+  EXPECT_EQ("switch (a) {\n"
+            "case 1:\n"
+            "  x = 8;\n"
+            "  // fall through\n"
+            "case 2: x = 8;\n"
+            "// comment\n"
+            "case 3:\n"
+            "  return; /* comment line 1\n"
+            "           * comment line 2 */\n"
+            "case 4: i = 8;\n"
+            "// something else\n"
+            "#if FOO\n"
+            "case 5: break;\n"
+            "#endif\n"
+            "}",
+            format("switch (a) {\n"
+                   "case 1: x = 8;\n"
+                   "  // fall through\n"
+                   "case 2:\n"
+                   "  x = 8;\n"
+                   "// comment\n"
+                   "case 3:\n"
+                   "  return; /* comment line 1\n"
+                   "           * comment line 2 */\n"
+                   "case 4:\n"
+                   "  i = 8;\n"
+                   "// something else\n"
+                   "#if FOO\n"
+                   "case 5: break;\n"
+                   "#endif\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));
+  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));
+  verifyFormat("switch (a) {\n"
                "#if FOO\n"
                "case 0: return 0;\n"
                "#endif\n"