Function docstring newlines

CHANGES.md

@@ -16,6 +16,7 @@
 
 - Remove unnecessary parentheses from `with` statements (#2926)
 - Standardise newlines after module-level docstrings (#2996)
+- Remove newlines after function docstrings (#1)
 
 ### _Blackd_
 

src/black/linegen.py

@@ -999,7 +999,6 @@ def maybe_make_parens_invisible_in_atom(
 
 def should_split_line(line: Line, opening_bracket: Leaf) -> bool:
     """Should `line` be immediately split with `delimiter_split()` after RHS?"""
-
     if not (opening_bracket.parent and opening_bracket.value in "[{("):
         return False
 
@@ -1034,7 +1033,6 @@ def generate_trailers_to_omit(line: Line, line_length: int) -> Iterator[Set[Leaf
     set is empty, unless the line should explode, in which case bracket pairs until
     the one that needs to explode are omitted.
     """
-
     omit: Set[LeafID] = set()
     if not line.magic_trailing_comma:
         yield omit

src/black/lines.py

@@ -522,8 +522,19 @@ def _maybe_empty_lines(self, current_line: Line) -> int:
             and self.previous_lines[-1].is_triple_quoted_string
             and current_line.depth == self.previous_lines[-1].depth
         ):
+            # Single newline after class docstring.
             return 1
 
+        if (
+            self.preview
+            and len(self.previous_lines) > 1
+            and self.previous_lines[-2].is_def
+            and self.previous_lines[-1].is_triple_quoted_string
+            and current_line.depth == self.previous_lines[-1].depth
+        ):
+            # No newline after function docstring.
+            return 0
+
         return before
 
     def _maybe_empty_lines_for_class_or_def(

src/black/parsing.py

@@ -193,7 +193,6 @@ def _normalize(lineend: str, value: str) -> str:
 
 def stringify_ast(node: Union[ast.AST, ast3.AST], depth: int = 0) -> Iterator[str]:
     """Simple visitor generating strings to compare ASTs by content."""
-
     node = fixup_ast_constants(node)
 
     yield f"{'  ' * depth}{node.__class__.__name__}("

src/black/trans.py

@@ -73,7 +73,6 @@ def TErr(err_msg: str) -> Err[CannotTransform]:
 
 def hug_power_op(line: Line, features: Collection[Feature]) -> Iterator[Line]:
     """A transformer which normalizes spacing around power operators."""
-
     # Performance optimization to avoid unnecessary Leaf clones and other ops.
     for leaf in line.leaves:
         if leaf.type == token.DOUBLESTAR:

tests/data/function_docstring.py

@@ -0,0 +1,30 @@
+def foo():
+    """hello world."""
+
+
+
+    print("hello world!")
+
+
+def bar(x: int, y: int) -> int:
+    """hello world.
+
+    blah blah blah...
+    """
+
+
+
+    return x + y
+
+# output
+def foo():
+    """hello world."""
+    print("hello world!")
+
+
+def bar(x: int, y: int) -> int:
+    """hello world.
+
+    blah blah blah...
+    """
+    return x + y

tests/test_format.py

@@ -85,6 +85,7 @@
     "one_element_subscript",
     "module_docstring_1",
     "module_docstring_2",
+    "function_docstring",
 ]
 
 SOURCES: List[str] = [