Allow empty lines at beginning of blocks (again) (#4060)

CHANGES.md

@@ -17,6 +17,8 @@
 - Standalone form feed characters at the module level are no longer removed (#4021)
 - Additional cases of immediately nested tuples, lists, and dictionaries are now
  indented less (#4012)
+- Allow empty lines at the beginning of all blocks, except immediately before a
+ docstring (#4060)
 - Fix crash in preview mode when using a short `--line-length` (#4086)
 
 ### Configuration

src/black/lines.py

@@ -689,18 +689,14 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
  return 0, 1
  return before, 1
 
+ # In preview mode, always allow blank lines, except right before a function
+ # docstring
  is_empty_first_line_ok = (
- Preview.allow_empty_first_line_before_new_block_or_comment
- in current_line.mode
+ Preview.allow_empty_first_line_in_block in current_line.mode
  and (
- # If it's a standalone comment
- current_line.leaves[0].type == STANDALONE_COMMENT
- # If it opens a new block
- or current_line.opens_block
- # If it's a triple quote comment (but not at the start of a funcdef)
+ not is_docstring(current_line.leaves[0])
  or (
- is_docstring(current_line.leaves[0])
- and self.previous_line
+ self.previous_line
  and self.previous_line.leaves[0]
  and self.previous_line.leaves[0].parent
  and not is_funcdef(self.previous_line.leaves[0].parent)

src/black/mode.py

@@ -191,7 +191,7 @@ class Preview(Enum):
  accept_raw_docstrings = auto()
  fix_power_op_line_length = auto()
  hug_parens_with_braces_and_square_brackets = auto()
- allow_empty_first_line_before_new_block_or_comment = auto()
+ allow_empty_first_line_in_block = auto()
  single_line_format_skip_with_multiple_comments = auto()
  long_case_block_line_splitting = auto()
  allow_form_feeds = auto()

tests/data/cases/preview_allow_empty_first_line_in_special_cases.py → tests/data/cases/preview_allow_empty_first_line.py

@@ -51,6 +51,17 @@ def baz():
  if x:
  a = 123
 
+def quux():
+
+ new_line = here
+
+
+class Cls:
+
+ def method(self):
+
+ pass
+
 # output
 
 def foo():
@@ -104,3 +115,14 @@ def baz():
  # OK
  if x:
  a = 123
+
+
+def quux():
+
+ new_line = here
+
+
+class Cls:
+ def method(self):
+
+ pass

tests/data/cases/preview_form_feeds.py

@@ -198,6 +198,7 @@ def foo():
 
 # form feeds are prohibited inside blocks, or on a line with nonwhitespace
 def bar(a=1, b: bool = False):
+
  pass