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from django.core.exceptions import ImproperlyConfigured
from django.db.models import Model
from django.db.models.base import ModelBase
from ..permissions import add_perm
class RulesModelBaseMixin:
"""
Mixin for the metaclass of Django's Model that allows declaring object-level
permissions in the model's Meta options.
If set, the Meta attribute "rules_permissions" has to be a dictionary with
permission types (like "add" or "change") as keys and predicates (like
rules.is_staff) as values. Permissions are then registered with the rules
framework automatically upon Model creation.
This mixin can be used for creating custom metaclasses.
"""
def __new__(cls, name, bases, attrs, **kwargs):
model_meta = attrs.get("Meta")
if hasattr(model_meta, "rules_permissions"):
perms = model_meta.rules_permissions
del model_meta.rules_permissions
if not isinstance(perms, dict):
raise ImproperlyConfigured(
"The rules_permissions Meta option of %s must be a dict, not %s."
% (name, type(perms))
)
perms = perms.copy()
else:
perms = {}
new_class = super().__new__(cls, name, bases, attrs, **kwargs)
new_class._meta.rules_permissions = perms
new_class.preprocess_rules_permissions(perms)
for perm_type, predicate in perms.items():
add_perm(new_class.get_perm(perm_type), predicate)
return new_class
class RulesModelBase(RulesModelBaseMixin, ModelBase):
"""
A subclass of Django's ModelBase with the RulesModelBaseMixin mixed in.
"""
class RulesModelMixin:
"""
A mixin for Django's Model that adds hooks for stepping into the process of
permission registration, which are called by the metaclass implementation in
RulesModelBaseMixin.
Use this mixin in a custom subclass of Model in order to change its behavior.
"""
@classmethod
def get_perm(cls, perm_type):
"""Converts permission type ("add") to permission name ("app.add_modelname")
:param perm_type: "add", "change", etc., or custom value
:type perm_type: str
:returns str:
"""
return "%s.%s_%s" % (cls._meta.app_label, perm_type, cls._meta.model_name)
@classmethod
def preprocess_rules_permissions(cls, perms):
"""May alter a permissions dict before it's processed further.
Use this, for instance, to alter the supplied permissions or insert default
values into the given dict.
:param perms:
Shallow-copied value of the rules_permissions model Meta option
:type perms: dict
"""
class RulesModel(RulesModelMixin, Model, metaclass=RulesModelBase):
"""
An abstract model with RulesModelMixin mixed in, using RulesModelBase as metaclass.
Use this as base for your models directly if you don't need to customize the
behavior of RulesModelMixin and thus don't want to create a custom base class.
"""
class Meta:
abstract = True
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