Ensure backwards compatibility when fetching a redis client

allianceauth/utils/cache.py

@@ -0,0 +1,21 @@
+from redis import Redis
+
+from django.core.cache import caches
+
+try:
+    import django_redis
+except ImportError:
+    django_redis = None
+
+
+def get_redis_client() -> Redis:
+    """Get the configured redis client used by Django for caching.
+
+    This function is a wrapper designed to work for both AA2 and AA3
+    and should always be used to ensure backwards compatibility.
+    """
+    try:
+        return django_redis.get_redis_connection("default")
+    except AttributeError:
+        default_cache = caches["default"]
+        return default_cache.get_master_client()

allianceauth/utils/tests/test_cache.py

@@ -0,0 +1,39 @@
+from unittest.mock import MagicMock, patch
+
+from django.test import TestCase
+
+from allianceauth.utils.cache import get_redis_client
+
+MODULE_PATH = "allianceauth.utils.cache"
+
+
+class RedisClientStub:
+    """Substitute for a Redis client."""
+
+    pass
+
+
+class TestGetRedisClient(TestCase):
+    def test_should_work_with_aa2_api(self):
+        # given
+        mock_django_cache = MagicMock()
+        mock_django_cache.get_master_client.return_value = RedisClientStub()
+        # when
+        with patch(MODULE_PATH + ".django_redis", None), patch.dict(
+            MODULE_PATH + ".caches", {"default": mock_django_cache}
+        ):
+            client = get_redis_client()
+        # then
+        self.assertIsInstance(client, RedisClientStub)
+
+    def test_should_work_with_aa3_api(self):
+        # given
+        mock_django_redis = MagicMock()
+        mock_django_redis.get_redis_connection.return_value = RedisClientStub()
+        # when
+        with patch(MODULE_PATH + ".django_redis", mock_django_redis), patch.dict(
+            MODULE_PATH + ".caches", {"default": None}
+        ):
+            client = get_redis_client()
+        # then
+        self.assertIsInstance(client, RedisClientStub)