[#154] Handle comments between decorators properly (#166)

black.py

@@ -1044,6 +1044,10 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
                 # Don't insert empty lines between decorators.
                 return 0, 0
 
+            if is_decorator and self.previous_line and self.previous_line.is_comment:
+                # Don't insert empty lines between decorator comments.
+                return 0, 0
+
             newlines = 2
             if current_line.depth:
                 newlines -= 1

tests/comments6.py

@@ -0,0 +1,8 @@
+@property
+# TODO: X
+@property
+# TODO: Y
+# TODO: Z
+@property
+def foo():
+    pass

tests/test_black.py

@@ -626,6 +626,14 @@ def test_check_diff_use_together(self) -> None:
             )
             self.assertEqual(result.exit_code, 1)
 
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_comment_in_decorator(self) -> None:
+        source, expected = read_data("comments6")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
 
 if __name__ == "__main__":
     unittest.main()