From 0892d9aa8f4b1905305b78ef5c144b6408eb85e0 Mon Sep 17 00:00:00 2001
From: Yurii Karabas <1998uriyyo@gmail.com>
Date: Tue, 16 Jul 2019 20:45:56 +0300
Subject: [PATCH] Use nullcontext in case when lock is None. Shutdown pool
 after code formatting. (#928)

(cherry picked from commit 90d205d1f50d4f801b3b3de3c40590eece10c4cd)
---
 black.py | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/black.py b/black.py
index 82cf6ff..b5aee4e 100644
--- a/black.py
+++ b/black.py
@@ -1,5 +1,6 @@
 import asyncio
 from concurrent.futures import Executor, ProcessPoolExecutor
+from contextlib import contextmanager
 from datetime import datetime
 from enum import Enum
 from functools import lru_cache, partial, wraps
@@ -523,6 +524,7 @@ def reformat_many(
         )
     finally:
         shutdown(loop)
+        executor.shutdown()
 
 
 async def schedule_formatting(
@@ -628,9 +630,8 @@ def format_file_in_place(
         src_name = f'{src}\t{then} +0000'
         dst_name = f'{src}\t{now} +0000'
         diff_contents = diff(src_contents, dst_contents, src_name, dst_name)
-        if lock:
-            lock.acquire()
-        try:
+
+        with lock or nullcontext():
             f = io.TextIOWrapper(
                 sys.stdout.buffer,
                 encoding=encoding,
@@ -639,9 +640,7 @@ def format_file_in_place(
             )
             f.write(diff_contents)
             f.detach()
-        finally:
-            if lock:
-                lock.release()
+
     return True
 
 
@@ -3593,6 +3592,13 @@ def dump_to_file(*output: str) -> str:
     return f.name
 
 
+@contextmanager
+def nullcontext() -> Iterator[None]:
+    """Return context manager that does nothing.
+    Similar to `nullcontext` from python 3.7"""
+    yield
+
+
 def diff(a: str, b: str, a_name: str, b_name: str) -> str:
     """Return a unified diff string between strings `a` and `b`."""
     import difflib