Fixed #29550 -- Eased overriding pickle.dumps() protocol in cache backends and session serializer.

django/contrib/sessions/serializers.py

@@ -8,8 +8,10 @@ class PickleSerializer:
     Simple wrapper around pickle to be used in signing.dumps and
     signing.loads.
     """
+    protocol = pickle.HIGHEST_PROTOCOL
+
     def dumps(self, obj):
-        return pickle.dumps(obj, pickle.HIGHEST_PROTOCOL)
+        return pickle.dumps(obj, self.protocol)
 
     def loads(self, data):
         return pickle.loads(data)

django/core/cache/backends/db.py

@@ -46,6 +46,8 @@ class DatabaseCache(BaseDatabaseCache):
     # conversion and adaptation infrastructure is then used to avoid comparing
     # aware and naive datetimes accidentally.
 
+    pickle_protocol = pickle.HIGHEST_PROTOCOL
+
     def get(self, key, default=None, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
@@ -130,7 +132,7 @@ class DatabaseCache(BaseDatabaseCache):
             exp = exp.replace(microsecond=0)
             if num > self._max_entries:
                 self._cull(db, cursor, now)
-            pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
+            pickled = pickle.dumps(value, self.pickle_protocol)
             # The DB column is expecting a string, so make sure the value is a
             # string, not bytes. Refs #19274.
             b64encoded = base64.b64encode(pickled).decode('latin1')

django/core/cache/backends/filebased.py

@@ -15,6 +15,7 @@ from django.core.files.move import file_move_safe
 
 class FileBasedCache(BaseCache):
     cache_suffix = '.djcache'
+    pickle_protocol = pickle.HIGHEST_PROTOCOL
 
     def __init__(self, dir, params):
         super().__init__(params)
@@ -39,8 +40,8 @@ class FileBasedCache(BaseCache):
 
     def _write_content(self, file, timeout, value):
         expiry = self.get_backend_timeout(timeout)
-        file.write(pickle.dumps(expiry, pickle.HIGHEST_PROTOCOL))
-        file.write(zlib.compress(pickle.dumps(value, pickle.HIGHEST_PROTOCOL)))
+        file.write(pickle.dumps(expiry, self.pickle_protocol))
+        file.write(zlib.compress(pickle.dumps(value, self.pickle_protocol)))
 
     def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         self._createdir()  # Cache dir can be deleted at any time.

django/core/cache/backends/locmem.py

@@ -14,6 +14,8 @@ _locks = {}
 
 
 class LocMemCache(BaseCache):
+    pickle_protocol = pickle.HIGHEST_PROTOCOL
+
     def __init__(self, name, params):
         super().__init__(params)
         self._cache = _caches.setdefault(name, OrderedDict())
@@ -23,7 +25,7 @@ class LocMemCache(BaseCache):
     def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
-        pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
+        pickled = pickle.dumps(value, self.pickle_protocol)
         with self._lock:
             if self._has_expired(key):
                 self._set(key, pickled, timeout)
@@ -51,7 +53,7 @@ class LocMemCache(BaseCache):
     def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
-        pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
+        pickled = pickle.dumps(value, self.pickle_protocol)
         with self._lock:
             self._set(key, pickled, timeout)
 
@@ -73,7 +75,7 @@ class LocMemCache(BaseCache):
             pickled = self._cache[key]
             value = pickle.loads(pickled)
             new_value = value + delta
-            pickled = pickle.dumps(new_value, pickle.HIGHEST_PROTOCOL)
+            pickled = pickle.dumps(new_value, self.pickle_protocol)
             self._cache[key] = pickled
             self._cache.move_to_end(key, last=False)
         return new_value