Add trailing comma when a single import doesn't fit on a line. (#504)

Fixes #250.

diff --git a/README.md b/README.md
index b56af4ab5baa3413548ee79f7e7579d2c1c99177..192f47ebe682d920ab0f2c6b46afcc6ffbaffe70 100644 (file)
--- a/README.md
+++ b/README.md
@@ -964,6 +964,8 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
   to be a bad idea (#415)
 
 
+* trailing comma is now added to single imports that don't fit on a line (#250)
+
 
 ### 18.6b4
 

diff --git a/black.py b/black.py
index 56765313aa85b0571c7831f209573bd2b3fbb955..f76f0ffc24cfcf237d13fcc19f5492635158c4c4 100644 (file)
--- a/black.py
+++ b/black.py
@@ -2209,7 +2209,7 @@ def left_hand_split(line: Line, py36: bool = False) -> Iterator[Line]:
             yield result
 
 
-def right_hand_split(
+def right_hand_split(  # noqa C901
     line: Line, line_length: int, py36: bool = False, omit: Collection[LeafID] = ()
 ) -> Iterator[Line]:
     """Split line into many lines, starting with the last matching bracket pair.
@@ -2250,6 +2250,9 @@ def right_hand_split(
         # the matching `opening_bracket` wasn't available on `line` anymore.
         raise CannotSplit("No brackets found")
 
+    if line.is_import and len(body_leaves) == 1:
+        body_leaves.append(Leaf(token.COMMA, ","))
+
     # Build the new lines.
     for result, leaves in (head, head_leaves), (body, body_leaves), (tail, tail_leaves):
         for leaf in leaves:

diff --git a/tests/data/import_spacing.py b/tests/data/import_spacing.py
index 0c98650f8339c56728442cdca93345d268c045c7..51cfda23ff355fa430e0a652d845283bfc6ac13d 100644 (file)
--- a/tests/data/import_spacing.py
+++ b/tests/data/import_spacing.py
@@ -86,7 +86,7 @@ from some_library import (
     Use,
 )
 from name_of_a_company.extremely_long_project_name.component.ttypes import (
-    CuteLittleServiceHandlerFactoryyy
+    CuteLittleServiceHandlerFactoryyy,
 )
 from name_of_a_company.extremely_long_project_name.extremely_long_component_name.ttypes import *