Replace pickle with JSON

Co-authored-by: Ivan Klass <klass.ivanklass@gmail.com>

AUTHORS

@@ -1,14 +1,18 @@
 Ales Zoulek <ales.zoulek@gmail.com>
-Alexander frenzel <alex@relatedworks.com>
+Alexander Frenzel <alex@relatedworks.com>
+Alexandr Artemyev <mogost@gmail.com>
 Bouke Haarsma <bouke@webatoom.nl>
 Camilo Nova <camilo.nova@gmail.com>
 Charlie Hornsby <charlie.hornsby@hotmail.co.uk>
 Curtis Maloney <curtis@tinbrain.net>
 Dan Poirier <dpoirier@caktusgroup.com>
 David Burke <dmbst32@gmail.com>
+Dmitriy Tatarkin <mail@dtatarkin.ru>
+Elisey Zanko <elisey.zanko@gmail.com>
 Florian Apolloner <florian@apolloner.eu>
 Igor Támara <igor@axiacore.com>
 Ilya Chichak <ilyachch@gmail.com>
+Ivan Klass <klass.ivanklass@gmail.com>
 Jake Merdich <jmerdich@users.noreply.github.com>
 Jannis Leidel <jannis@leidel.info>
 Janusz Harkot <janusz.harkot@gmail.com>
@@ -32,6 +36,7 @@ Pierre-Olivier Marec <pomarec@free.fr>
 Roman Krejcik <farin@farin.cz>
 Silvan Spross <silvan.spross@gmail.com>
 Sławek Ehlert <slafs@op.pl>
+Vladas Tamoshaitis <amd.vladas@gmail.com>
 Vojtech Jasny <voy@voy.cz>
 Yin Jifeng <jifeng.yin@gmail.com>
 illumin-us-r3v0lution <luminaries@riseup.net>
@@ -40,7 +45,3 @@ saw2th <stephen@saw2th.co.uk>
 trbs <trbs@trbs.net>
 vl <1844144@gmail.com>
 vl <vl@u64.(none)>
-Vladas Tamoshaitis <amd.vladas@gmail.com>
-Dmitriy Tatarkin <mail@dtatarkin.ru>
-Alexandr Artemyev <mogost@gmail.com>
-Elisey Zanko <elisey.zanko@gmail.com>

constance/backends/database.py

@@ -11,6 +11,8 @@
 from constance import settings
 from constance import signals
 from constance.backends import Backend
+from constance.codecs import dumps
+from constance.codecs import loads
 
 
 class DatabaseBackend(Backend):
@@ -64,7 +66,7 @@ def mget(self, keys):
         try:
             stored = self._model._default_manager.filter(key__in=keys)
             for const in stored:
-                yield keys[const.key], const.value
+                yield keys[const.key], loads(const.value)
         except (OperationalError, ProgrammingError):
             pass
 
@@ -79,7 +81,7 @@ def get(self, key):
         if value is None:
             match = self._model._default_manager.filter(key=key).first()
             if match:
-                value = match.value
+                value = loads(match.value)
                 if self._cache:
                     self._cache.add(key, value)
         return value
@@ -100,16 +102,16 @@ def set(self, key, value):
         except self._model.DoesNotExist:
             try:
                 with transaction.atomic(using=queryset.db):
-                    queryset.create(key=key, value=value)
+                    queryset.create(key=key, value=dumps(value))
                 created = True
             except IntegrityError:
                 # Allow concurrent writes
                 constance = queryset.get(key=key)
 
         if not created:
-            old_value = constance.value
-            constance.value = value
-            constance.save()
+            old_value = loads(constance.value)
+            constance.value = dumps(value)
+            constance.save(update_fields=['value'])
         else:
             old_value = None
 

constance/backends/redisd.py

@@ -1,5 +1,3 @@
-from pickle import dumps
-from pickle import loads
 from threading import RLock
 from time import monotonic
 
@@ -9,8 +7,9 @@
 from constance import settings
 from constance import signals
 from constance import utils
-
-from . import Backend
+from constance.backends import Backend
+from constance.codecs import dumps
+from constance.codecs import loads
 
 
 class RedisBackend(Backend):
@@ -36,7 +35,7 @@ def add_prefix(self, key):
     def get(self, key):
         value = self._rd.get(self.add_prefix(key))
         if value:
-            return loads(value)  # noqa: S301
+            return loads(value)
         return None
 
     def mget(self, keys):
@@ -45,11 +44,11 @@ def mget(self, keys):
         prefixed_keys = [self.add_prefix(key) for key in keys]
         for key, value in zip(keys, self._rd.mget(prefixed_keys)):
             if value:
-                yield key, loads(value)  # noqa: S301
+                yield key, loads(value)
 
     def set(self, key, value):
         old_value = self.get(key)
-        self._rd.set(self.add_prefix(key), dumps(value, protocol=settings.REDIS_PICKLE_VERSION))
+        self._rd.set(self.add_prefix(key), dumps(value))
         signals.config_updated.send(sender=config, key=key, old_value=old_value, new_value=value)
 
 

constance/codecs.py

@@ -0,0 +1,93 @@
+from __future__ import annotations
+
+import json
+import logging
+import uuid
+from datetime import date
+from datetime import datetime
+from datetime import time
+from datetime import timedelta
+from decimal import Decimal
+from typing import Any
+from typing import Protocol
+from typing import TypeVar
+
+logger = logging.getLogger(__name__)
+
+DEFAULT_DISCRIMINATOR = 'default'
+
+
+class JSONEncoder(json.JSONEncoder):
+    """Django-constance custom json encoder."""
+
+    def default(self, o):
+        for discriminator, (t, _, encoder) in _codecs.items():
+            if isinstance(o, t):
+                return _as(discriminator, encoder(o))
+        raise TypeError(f'Object of type {o.__class__.__name__} is not JSON serializable')
+
+
+def _as(discriminator: str, v: Any) -> dict[str, Any]:
+    return {'__type__': discriminator, '__value__': v}
+
+
+def dumps(obj, _dumps=json.dumps, cls=JSONEncoder, default_kwargs=None, **kwargs):
+    """Serialize object to json string."""
+    default_kwargs = default_kwargs or {}
+    is_default_type = isinstance(obj, (str, int, bool, float, type(None)))
+    return _dumps(
+        _as(DEFAULT_DISCRIMINATOR, obj) if is_default_type else obj, cls=cls, **dict(default_kwargs, **kwargs)
+    )
+
+
+def loads(s, _loads=json.loads, **kwargs):
+    """Deserialize json string to object."""
+    return _loads(s, object_hook=object_hook, **kwargs)
+
+
+def object_hook(o: dict) -> Any:
+    """Hook function to perform custom deserialization."""
+    if o.keys() == {'__type__', '__value__'}:
+        if o['__type__'] == DEFAULT_DISCRIMINATOR:
+            return o['__value__']
+        codec = _codecs.get(o['__type__'])
+        if not codec:
+            raise ValueError('Unsupported type', type, o)
+        return codec[1](o['__value__'])
+    logger.error('Cannot deserialize object: %s', o)
+    raise ValueError('Invalid object', o)
+
+
+T = TypeVar('T')
+
+
+class Encoder(Protocol[T]):
+    def __call__(self, value: T, /) -> str: ...
+
+
+class Decoder(Protocol[T]):
+    def __call__(self, value: str, /) -> T: ...
+
+
+def register_type(t: type[T], discriminator: str, encoder: Encoder[T], decoder: Decoder[T]):
+    if not discriminator:
+        raise ValueError('Discriminator must be specified')
+    if _codecs.get(discriminator) or discriminator == DEFAULT_DISCRIMINATOR:
+        raise ValueError(f'Type with discriminator {discriminator} is already registered')
+    _codecs[discriminator] = (t, decoder, encoder)
+
+
+_codecs: dict[str, tuple[type, Decoder, Encoder]] = {}
+
+
+def _register_default_types():
+    # NOTE: datetime should be registered before date, because datetime is also instance of date.
+    register_type(datetime, 'datetime', datetime.isoformat, datetime.fromisoformat)
+    register_type(date, 'date', lambda o: o.isoformat(), lambda o: datetime.fromisoformat(o).date())
+    register_type(time, 'time', lambda o: o.isoformat(), time.fromisoformat)
+    register_type(Decimal, 'decimal', str, Decimal)
+    register_type(uuid.UUID, 'uuid', lambda o: o.hex, uuid.UUID)
+    register_type(timedelta, 'timedelta', lambda o: o.total_seconds(), lambda o: timedelta(seconds=o))
+
+
+_register_default_types()

constance/migrations/0001_initial.py

@@ -1,4 +1,3 @@
-import picklefield.fields
 from django.db import migrations
 from django.db import models
 
@@ -14,7 +13,7 @@ class Migration(migrations.Migration):
             fields=[
                 ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                 ('key', models.CharField(max_length=255, unique=True)),
-                ('value', picklefield.fields.PickledObjectField(blank=True, editable=False, null=True)),
+                ('value', models.TextField(blank=True, editable=False, null=True)),
             ],
             options={
                 'verbose_name': 'constance',

constance/migrations/0003_drop_pickle.py

@@ -0,0 +1,53 @@
+import logging
+import pickle
+from base64 import b64decode
+from importlib import import_module
+
+from django.db import migrations
+
+from constance import settings
+from constance.codecs import dumps
+
+logger = logging.getLogger(__name__)
+
+
+def import_module_attr(path):
+    package, module = path.rsplit('.', 1)
+    return getattr(import_module(package), module)
+
+
+def migrate_pickled_data(apps, schema_editor) -> None:
+    Constance = apps.get_model('constance', 'Constance')
+
+    for constance in Constance.objects.exclude(value=None):
+        constance.value = dumps(pickle.loads(b64decode(constance.value.encode())))  # noqa: S301
+        constance.save(update_fields=['value'])
+
+    if settings.BACKEND in ('constance.backends.redisd.RedisBackend', 'constance.backends.redisd.CachingRedisBackend'):
+        import redis
+
+        _prefix = settings.REDIS_PREFIX
+        connection_cls = settings.REDIS_CONNECTION_CLASS
+        if connection_cls is not None:
+            _rd = import_module_attr(connection_cls)()
+        else:
+            if isinstance(settings.REDIS_CONNECTION, str):
+                _rd = redis.from_url(settings.REDIS_CONNECTION)
+            else:
+                _rd = redis.Redis(**settings.REDIS_CONNECTION)
+        redis_migrated_data = {}
+        for key in settings.CONFIG:
+            prefixed_key = f'{_prefix}{key}'
+            value = _rd.get(prefixed_key)
+            if value is not None:
+                redis_migrated_data[prefixed_key] = dumps(pickle.loads(value))  # noqa: S301
+        for prefixed_key, value in redis_migrated_data.items():
+            _rd.set(prefixed_key, value)
+
+
+class Migration(migrations.Migration):
+    dependencies = [('constance', '0002_migrate_from_old_table')]
+
+    operations = [
+        migrations.RunPython(migrate_pickled_data),
+    ]

constance/models.py

@@ -1,20 +1,10 @@
-from django.core.exceptions import ImproperlyConfigured
 from django.db import models
 from django.utils.translation import gettext_lazy as _
 
-try:
-    from picklefield import PickledObjectField
-except ImportError:
-    raise ImproperlyConfigured(
-        "Couldn't find the the 3rd party app "
-        'django-picklefield which is required for '
-        'the constance database backend.'
-    ) from None
-
 
 class Constance(models.Model):
     key = models.CharField(max_length=255, unique=True)
-    value = PickledObjectField(null=True, blank=True)
+    value = models.TextField(null=True, blank=True)
 
     class Meta:
         verbose_name = _('constance')

constance/settings.py

@@ -1,5 +1,3 @@
-import pickle
-
 from django.conf import settings
 
 BACKEND = getattr(settings, 'CONSTANCE_BACKEND', 'constance.backends.redisd.RedisBackend')
@@ -26,8 +24,6 @@
 
 REDIS_CONNECTION = getattr(settings, 'CONSTANCE_REDIS_CONNECTION', {})
 
-REDIS_PICKLE_VERSION = getattr(settings, 'CONSTANCE_REDIS_PICKLE_VERSION', pickle.DEFAULT_PROTOCOL)
-
 SUPERUSER_ONLY = getattr(settings, 'CONSTANCE_SUPERUSER_ONLY', True)
 
 IGNORE_ADMIN_VERSION_CHECK = getattr(settings, 'CONSTANCE_IGNORE_ADMIN_VERSION_CHECK', False)

docs/backends.rst

@@ -74,16 +74,6 @@ database. Defaults to ``'constance:'``. E.g.::
 
     CONSTANCE_REDIS_PREFIX = 'constance:myproject:'
 
-``CONSTANCE_REDIS_PICKLE_VERSION``
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The (optional) protocol version of pickle you want to use to serialize your python
-objects when storing in the Redis database. Defaults to ``pickle.DEFAULT_PROTOCOL``. E.g.::
-
-    CONSTANCE_REDIS_PICKLE_VERSION = pickle.DEFAULT_PROTOCOL
-
-You might want to pin this value to a specific protocol number, since ``pickle.DEFAULT_PROTOCOL``
-means different things between versions of Python.
 
 ``CONSTANCE_REDIS_CACHE_TIMEOUT``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -94,9 +84,7 @@ Defaults to `60` seconds.
 Database
 --------
 
-Database backend stores configuration values in a
-standard Django model. It requires the package `django-picklefield`_ for
-storing those values.
+Database backend stores configuration values in a standard Django model.
 
 You must set the ``CONSTANCE_BACKEND`` Django setting to::
 
@@ -161,8 +149,6 @@ configured cache backend to enable this feature, e.g. "default"::
           simply set the :setting:`CONSTANCE_DATABASE_CACHE_AUTOFILL_TIMEOUT`
           setting to ``None``.
 
-.. _django-picklefield: https://pypi.org/project/django-picklefield/
-
 Memory
 ------
 

pyproject.toml

@@ -34,9 +34,6 @@ classifiers = [
     "Programming Language :: Python :: Implementation :: CPython",
     "Topic :: Utilities",
 ]
-dependencies = [
-    "django-picklefield",
-]
 
 [project.optional-dependencies]
 redis = [