Class new line between docstrings / vars / methods (#219)

Partially addresses #144

black.py

@@ -987,6 +987,18 @@ def is_class_paren_empty(self) -> bool:
             and self.leaves[3].value == ")"
         )
 
+    @property
+    def is_triple_quoted_string(self) -> bool:
+        """Is the line a triple quoted docstring?"""
+        return (
+            bool(self)
+            and self.leaves[0].type == token.STRING
+            and (
+                self.leaves[0].value.startswith('"""')
+                or self.leaves[0].value.startswith("'''")
+            )
+        )
+
     def contains_standalone_comments(self, depth_limit: int = sys.maxsize) -> bool:
         """If so, needs to be split before emitting."""
         for leaf in self.leaves:
@@ -1194,6 +1206,7 @@ class EmptyLineTracker:
     the prefix of the first leaf consists of optional newlines.  Those newlines
     are consumed by `maybe_empty_lines()` and included in the computation.
     """
+
     is_pyi: bool = False
     previous_line: Optional[Line] = None
     previous_after: int = 0
@@ -1244,6 +1257,12 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
             if self.previous_line.is_decorator:
                 return 0, 0
 
+            if (
+                self.previous_line.is_class
+                and self.previous_line.depth != current_line.depth
+            ):
+                return 0, 0
+
             if (
                 self.previous_line.is_comment
                 and self.previous_line.depth == current_line.depth
@@ -1275,6 +1294,13 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
         ):
             return (before or 1), 0
 
+        if (
+            self.previous_line
+            and self.previous_line.is_class
+            and current_line.is_triple_quoted_string
+        ):
+            return before, 1
+
         return before, 0
 
 
@@ -1285,6 +1311,7 @@ class LineGenerator(Visitor[Line]):
     Note: destroys the tree it's visiting by mutating prefixes of its leaves
     in ways that will no longer stringify to valid Python code on the tree.
     """
+
     is_pyi: bool = False
     current_line: Line = Factory(Line)
     remove_u_prefix: bool = False
@@ -2768,6 +2795,7 @@ def gen_python_files_in_dir(path: Path) -> Iterator[Path]:
 @dataclass
 class Report:
     """Provides a reformatting counter. Can be rendered with `str(report)`."""
+
     check: bool = False
     quiet: bool = False
     change_count: int = 0

tests/class_blank_parentheses.py

@@ -39,7 +39,6 @@ def test_func(self):
 
 
 class ClassWithEmptyFunc(object):
-
     def func_with_blank_parentheses():
         return 5
 
@@ -55,7 +54,6 @@ class InsideFunc:
 
 
 class NormalClass:
-
     def func_for_testing(self, first, second):
         sum = first + second
         return sum

tests/class_methods_new_line.py

@@ -0,0 +1,42 @@
+class ClassSimplest:
+    pass
+class ClassWithInit:
+    def __init__(self):
+        pass
+class ClassWithInitAndVars:
+    cls_var = 100
+    def __init__(self):
+        pass
+class ClassWithInitAndVarsAndDocstring:
+    """Test class"""
+    cls_var = 100
+    def __init__(self):
+        pass
+
+
+# output
+
+
+class ClassSimplest:
+    pass
+
+
+class ClassWithInit:
+    def __init__(self):
+        pass
+
+
+class ClassWithInitAndVars:
+    cls_var = 100
+
+    def __init__(self):
+        pass
+
+
+class ClassWithInitAndVarsAndDocstring:
+    """Test class"""
+
+    cls_var = 100
+
+    def __init__(self):
+        pass

tests/comments4.py

@@ -1,5 +1,4 @@
 class C:
-
     @pytest.mark.parametrize(
         ("post_data", "message"),
         [

tests/composition.py

@@ -1,5 +1,4 @@
 class C:
-
     def test(self) -> None:
         with patch("black.out", print):
             self.assertEqual(

tests/test_black.py

@@ -363,6 +363,14 @@ def test_remove_empty_parentheses_after_class(self) -> None:
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, line_length=ll)
 
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_new_line_between_class_and_code(self) -> None:
+        source, expected = read_data("class_methods_new_line")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
     def test_report(self) -> None:
         report = black.Report()
         out_lines = []