Fix: Make URL cache clearing thread-safe in _django_set_urlconf

Author: pankaj-bind

pytest_django/plugin.py

@@ -16,6 +16,7 @@
 from contextlib import AbstractContextManager
 from functools import reduce
 from typing import TYPE_CHECKING, NoReturn
+import threading
 
 import pytest
 
@@ -64,6 +65,8 @@
 
 # ############### pytest hooks ################
 
+urlconf_lock = threading.Lock()
+
 
 @pytest.hookimpl()
 def pytest_addoption(parser: pytest.Parser) -> None:
@@ -646,20 +649,20 @@ def _django_set_urlconf(request: pytest.FixtureRequest) -> Generator[None, None,
         import django.conf
         from django.urls import clear_url_caches, set_urlconf
 
-        urls = validate_urls(marker)
-        original_urlconf = django.conf.settings.ROOT_URLCONF
-        django.conf.settings.ROOT_URLCONF = urls
-        clear_url_caches()
-        set_urlconf(None)
+        with urlconf_lock:
+            urls = validate_urls(marker)
+            original_urlconf = django.conf.settings.ROOT_URLCONF
+            django.conf.settings.ROOT_URLCONF = urls
+            clear_url_caches()
+            set_urlconf(None)
 
     yield
 
     if marker:
-        django.conf.settings.ROOT_URLCONF = original_urlconf
-        # Copy the pattern from
-        # https://github.com/django/django/blob/main/django/test/signals.py#L152
-        clear_url_caches()
-        set_urlconf(None)
+        with urlconf_lock:
+            django.conf.settings.ROOT_URLCONF = original_urlconf
+            clear_url_caches()
+            set_urlconf(None)
 
 
 @pytest.fixture(autouse=True, scope="session")

tests/test_urls.py

@@ -107,3 +107,46 @@ def test_something_else():
 
     result = django_pytester.runpytest_subprocess()
     assert result.ret == 0
+
+@pytest.mark.django_project(
+    extra_settings="""
+    ROOT_URLCONF = "empty"
+    """
+)
+def test_urls_concurrent(django_pytester: DjangoPytester) -> None:
+    "Test that the URL cache clearing is thread-safe with pytest-xdist."
+    pytest.importorskip("xdist")
+
+    django_pytester.makepyfile(
+        empty="urlpatterns = []",
+        urls1="""
+        from django.urls import path
+        urlpatterns = [path('url1/', lambda r: None, name='url1')]
+        """,
+        urls2="""
+        from django.urls import path
+        urlpatterns = [path('url2/', lambda r: None, name='url2')]
+        """,
+    )
+
+    django_pytester.create_test_module(
+        """
+        import pytest
+        from django.urls import reverse, NoReverseMatch
+
+        @pytest.mark.urls('urls1')
+        def test_urls1():
+            reverse('url1')
+            with pytest.raises(NoReverseMatch):
+                reverse('url2')
+
+        @pytest.mark.urls('urls2')
+        def test_urls2():
+            reverse('url2')
+            with pytest.raises(NoReverseMatch):
+                reverse('url1')
+        """
+    )
+
+    result = django_pytester.runpytest_subprocess("-n", "2")
+    assert result.ret == 0