Support sticky standalone comments (comments preceding defs, classes, and decorators)

Fixes #56
Fixes #154

README.md

@@ -230,11 +230,9 @@ are always reformatted to fit minimal space, this whitespace is lost.
 
 It will also insert proper spacing before and after function definitions.
 It's one line before and after inner functions and two lines before and
-after module-level functions.  *Black* will put those empty lines also
+after module-level functions.  *Black* will not put empty lines between
-between the function definition and any standalone comments that
+function/class definitions and standalone comments that immediately precede
-immediately precede the given function.  If you want to comment on the
+the given function/class.
-entire function, use a docstring or put a leading comment in the function
-body.
 
 
 ### Trailing commas
@@ -532,6 +530,9 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
 
 * fixed comment indentation when a standalone comment closes a block (#16, #32)
 
+* fixed standalone comments receiving extra empty lines if immediately preceding
+  a class, def, or decorator (#56, #154)
+
 * fixed `--diff` not showing entire path (#130)
 
 * fixed parsing of complex expressions after star and double stars in

black.py

@@ -1040,12 +1040,14 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
                 # Don't insert empty lines before the first line in the file.
                 return 0, 0
 
-            if self.previous_line and self.previous_line.is_decorator:
+            if self.previous_line.is_decorator:
-                # Don't insert empty lines between decorators.
                 return 0, 0
 
-            if is_decorator and self.previous_line and self.previous_line.is_comment:
+            if (
-                # Don't insert empty lines between decorator comments.
+                self.previous_line.is_comment
+                and self.previous_line.depth == current_line.depth
+                and before == 0
+            ):
                 return 0, 0
 
             newlines = 2

tests/comments2.py

@@ -161,8 +161,6 @@ def inline_comments_in_brackets_ruin_everything():
     # add_compiler(compilers[(7.1, 64)])
 
 # Comment before function.
-
-
 def inline_comments_in_brackets_ruin_everything():
     if typedargslist:
         parameters.children = [

tests/comments5.py

@@ -27,5 +27,45 @@
 except OSError:
     print("problems")
 
+import sys
+
+
+# leading function comment
+def wat():
+    ...
+    # trailing function comment
+
+
+# SECTION COMMENT
+
+
+# leading 1
+@deco1
+# leading 2
+@deco2(with_args=True)
+# leading 3
+@deco3
+def decorated1():
+    ...
+
+
+# leading 1
+@deco1
+# leading 2
+@deco2(with_args=True)
+# leading function comment
+def decorated1():
+    ...
+
+
+# Note: crappy but inevitable.  The current design of EmptyLineTracker doesn't
+# allow this to work correctly.  The user will have to split those lines by
+# hand.
+some_instruction
+# This comment should be split from `some_instruction` by two lines but isn't.
+def g():
+    ...
+
+
 if __name__ == "__main__":
     main()

tests/comments6.py

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

tests/empty_lines.py

@@ -1,3 +1,7 @@
+"""Docstring."""
+
+
+# leading comment
 def f():
     NO = ''
     SPACE = ' '
@@ -44,9 +48,11 @@ def f():
                 syms.dictsetmaker,
             }:
                 return NO
+
 ###############################################################################
 # SECTION BECAUSE SECTIONS
 ###############################################################################
+
 def g():
     NO = ''
     SPACE = ' '
@@ -89,6 +95,10 @@ def g():
 # output
 
 
+"""Docstring."""
+
+
+# leading comment
 def f():
     NO = ""
     SPACE = " "

tests/fmtonoff.py

@@ -119,8 +119,6 @@ async def coroutine(arg, exec=False):
 def function_signature_stress_test(number:int,no_annotation=None,text:str='default',* ,debug:bool=False,**kwargs) -> str:
  return text[number:-1]
 # fmt: on
-
-
 def spaces(a=1, b=(), c=[], d={}, e=True, f=-1, g=1 if False else 2, h="", i=r""):
     offset = attr.ib(default=attr.Factory(lambda: _r.uniform(10000, 200000)))
     assert task._cancel_stack[:len(old_stack)] == old_stack

tests/test_black.py

@@ -626,14 +626,6 @@ 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()