From 7be6a6a4d665061e8bc6a741b16ff92353f5d19e Mon Sep 17 00:00:00 2001
From: Hasan Ramezani <hasan.r67@gmail.com>
Date: Fri, 11 Sep 2020 11:48:40 +0200
Subject: [PATCH] Fixed #31989 -- Fixed return value of
 django.core.files.locks.lock()/unlock() on POSIX systems.

---
 django/core/files/locks.py | 11 +++++++----
 docs/releases/3.2.txt      |  4 ++++
 tests/files/tests.py       | 18 +++++++++++++++++-
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/django/core/files/locks.py b/django/core/files/locks.py
index c46b00b905..b02faaa181 100644
--- a/django/core/files/locks.py
+++ b/django/core/files/locks.py
@@ -107,9 +107,12 @@ else:
             return True
     else:
         def lock(f, flags):
-            ret = fcntl.flock(_fd(f), flags)
-            return ret == 0
+            try:
+                fcntl.flock(_fd(f), flags)
+                return True
+            except BlockingIOError:
+                return False
 
         def unlock(f):
-            ret = fcntl.flock(_fd(f), fcntl.LOCK_UN)
-            return ret == 0
+            fcntl.flock(_fd(f), fcntl.LOCK_UN)
+            return True
diff --git a/docs/releases/3.2.txt b/docs/releases/3.2.txt
index 30cc6a401a..e77785f8e2 100644
--- a/docs/releases/3.2.txt
+++ b/docs/releases/3.2.txt
@@ -504,6 +504,10 @@ Miscellaneous
   distinguishes inherited field instances across models. Additionally, the
   ordering of such fields is now defined.
 
+* The undocumented ``django.core.files.locks.lock()`` function now returns
+  ``False`` if the file cannot be locked, instead of raising
+  :exc:`BlockingIOError`.
+
 .. _deprecated-features-3.2:
 
 Features deprecated in 3.2
diff --git a/tests/files/tests.py b/tests/files/tests.py
index 047c8935b8..dfb007f2fc 100644
--- a/tests/files/tests.py
+++ b/tests/files/tests.py
@@ -8,7 +8,7 @@ from io import BytesIO, StringIO, TextIOWrapper
 from pathlib import Path
 from unittest import mock
 
-from django.core.files import File
+from django.core.files import File, locks
 from django.core.files.base import ContentFile
 from django.core.files.move import file_move_safe
 from django.core.files.temp import NamedTemporaryFile
@@ -169,6 +169,22 @@ class FileTests(unittest.TestCase):
             test_file.seek(0)
             self.assertEqual(test_file.read(), (content * 2).encode())
 
+    def test_exclusive_lock(self):
+        file_path = Path(__file__).parent / 'test.png'
+        with open(file_path) as f1, open(file_path) as f2:
+            self.assertIs(locks.lock(f1, locks.LOCK_EX), True)
+            self.assertIs(locks.lock(f2, locks.LOCK_EX | locks.LOCK_NB), False)
+            self.assertIs(locks.lock(f2, locks.LOCK_SH | locks.LOCK_NB), False)
+            self.assertIs(locks.unlock(f1), True)
+
+    def test_shared_lock(self):
+        file_path = Path(__file__).parent / 'test.png'
+        with open(file_path) as f1, open(file_path) as f2:
+            self.assertIs(locks.lock(f1, locks.LOCK_SH), True)
+            self.assertIs(locks.lock(f2, locks.LOCK_SH | locks.LOCK_NB), True)
+            self.assertIs(locks.unlock(f1), True)
+            self.assertIs(locks.unlock(f2), True)
+
 
 class NoNameFileTestCase(unittest.TestCase):
     """