Merge pull request #335 from SmileyChris/pymemcache

Add `pymemcache` cache backend for Django 3.2+

docs/types.rst

@@ -34,8 +34,10 @@ Supported types
   * Dummy: ``dummycache://``
   * File: ``filecache://``
   * Memory: ``locmemcache://``
-  * Memcached: ``memcache://``
-  * Python memory: ``pymemcache://``
+  * Memcached:
+    * ``memcache://`` (uses ``python-memcached`` backend, deprecated in Django 3.2)
+    * ``pymemcache://`` (uses ``pymemcache`` backend if Django >=3.2 and package is installed, otherwise will use ``pylibmc`` backend to keep config backwards compatibility)
+    * ``pylibmc://``
   * Redis: ``rediscache://``, ``redis://``, or ``rediss://``
 
 * ``search_url``

environ/compat.py

@@ -8,15 +8,15 @@
 
 """This module handles import compatibility issues."""
 
-import pkgutil
+from pkgutil import find_loader
 
 
-if pkgutil.find_loader('simplejson'):
+if find_loader('simplejson'):
     import simplejson as json
 else:
     import json
 
-if pkgutil.find_loader('django'):
+if find_loader('django'):
     from django import VERSION as DJANGO_VERSION
     from django.core.exceptions import ImproperlyConfigured
 else:
@@ -33,7 +33,20 @@ class ImproperlyConfigured(Exception):
     DJANGO_POSTGRES = 'django.db.backends.postgresql'
 
 # back compatibility with redis_cache package
-if pkgutil.find_loader('redis_cache'):
+if find_loader('redis_cache'):
     REDIS_DRIVER = 'redis_cache.RedisCache'
 else:
     REDIS_DRIVER = 'django_redis.cache.RedisCache'
+
+
+# back compatibility for pymemcache
+def choose_pymemcache_driver():
+    old_django = DJANGO_VERSION is not None and DJANGO_VERSION < (3, 2)
+    if old_django or not find_loader('pymemcache'):
+        # The original backend choice for the 'pymemcache' scheme is
+        # unfortunately 'pylibmc'.
+        return 'django.core.cache.backends.memcached.PyLibMCCache'
+    return 'django.core.cache.backends.memcached.PyMemcacheCache'
+
+
+PYMEMCACHE_DRIVER = choose_pymemcache_driver()

environ/environ.py

@@ -26,7 +26,13 @@
     urlunparse,
 )
 
-from .compat import DJANGO_POSTGRES, ImproperlyConfigured, json, REDIS_DRIVER
+from .compat import (
+    DJANGO_POSTGRES,
+    ImproperlyConfigured,
+    json,
+    PYMEMCACHE_DRIVER,
+    REDIS_DRIVER,
+)
 from .fileaware_mapping import FileAwareMapping
 
 try:
@@ -116,7 +122,8 @@ class Env:
         'filecache': 'django.core.cache.backends.filebased.FileBasedCache',
         'locmemcache': 'django.core.cache.backends.locmem.LocMemCache',
         'memcache': 'django.core.cache.backends.memcached.MemcachedCache',
-        'pymemcache': 'django.core.cache.backends.memcached.PyLibMCCache',
+        'pymemcache': PYMEMCACHE_DRIVER,
+        'pylibmc': 'django.core.cache.backends.memcached.PyLibMCCache',
         'rediscache': REDIS_DRIVER,
         'redis': REDIS_DRIVER,
         'rediss': REDIS_DRIVER,

tests/test_cache.py

@@ -6,10 +6,13 @@
 # For the full copyright and license information, please view
 # the LICENSE.txt file that was distributed with this source code.
 
+from unittest import mock
+
 import pytest
 
+import environ.compat
 from environ import Env
-from environ.compat import REDIS_DRIVER, ImproperlyConfigured
+from environ.compat import PYMEMCACHE_DRIVER, REDIS_DRIVER, ImproperlyConfigured
 
 
 def test_base_options_parsing():
@@ -63,7 +66,7 @@ def test_base_options_parsing():
          'django.core.cache.backends.memcached.MemcachedCache',
          '127.0.0.1:11211'),
         ('pymemcache://127.0.0.1:11211',
-         'django.core.cache.backends.memcached.PyLibMCCache',
+         PYMEMCACHE_DRIVER,
          '127.0.0.1:11211'),
     ],
     ids=[
@@ -90,6 +93,21 @@ def test_cache_parsing(url, backend, location):
     assert url['LOCATION'] == location
 
 
+@pytest.mark.parametrize('django_version', ((3, 2), (3, 1), None))
+@pytest.mark.parametrize('pymemcache_installed', (True, False))
+def test_pymemcache_compat(django_version, pymemcache_installed):
+    old = 'django.core.cache.backends.memcached.PyLibMCCache'
+    new = 'django.core.cache.backends.memcached.PyMemcacheCache'
+    with mock.patch.object(environ.compat, 'DJANGO_VERSION', django_version):
+        with mock.patch('environ.compat.find_loader') as mock_find_loader:
+            mock_find_loader.return_value = pymemcache_installed
+            driver = environ.compat.choose_pymemcache_driver()
+            if django_version and django_version < (3, 2):
+                assert driver == old
+            else:
+                assert driver == new if pymemcache_installed else old
+
+
 def test_redis_parsing():
     url = ('rediscache://127.0.0.1:6379/1?client_class='
            'django_redis.client.DefaultClient&password=secret')