PonyORM with mixins with custom hash - ponyorm

Question

I have a (in this case) mixin class that defines its own hash and eq. When mixing this into a Pony Entity evil things happen:
from pony.orm import Database, Optional, Required
db = Database()
class RoleMixin:
def __hash__(self):
return hash(self.name)
def __eq__(self, other):
return self.name == other or self.name == getattr(other, "name", None)
def get_permissions(self):
if self.permissions:
return self.permissions
return set()
class Role(db.Entity, RoleMixin):
name = Required(str, unique=True)
description = Optional(str, nullable=True)
permissions = Optional(str, nullable=True)
db.bind("sqlite", ":memory:", create_db=True)
db.generate_mapping(create_tables=True)
role = Role(name="admin")
print(role)
And when running this:
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/utils/utils.py", line 78, in cut_traceback
reraise(exc_type, exc, full_tb)
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/utils/utils.py", line 95, in reraise
try: raise exc.with_traceback(tb)
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/utils/utils.py", line 61, in cut_traceback
try: return func(*args, **kwargs)
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/orm/core.py", line 4721, in __init__
entity._get_from_identity_map_(pkval, 'created', undo_funcs=undo_funcs, obj_to_init=obj)
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/orm/core.py", line 4416, in _get_from_identity_map_
cache.objects.add(obj)
File "/Users/jwag/fs/flask-security/flask_security/ponydbg.py", line 8, in __hash__
return hash(self.name)
File "<string>", line 2, in __get__
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/utils/utils.py", line 78, in cut_traceback
reraise(exc_type, exc, full_tb)
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/utils/utils.py", line 95, in reraise
try: raise exc.with_traceback(tb)
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/utils/utils.py", line 61, in cut_traceback
try: return func(*args, **kwargs)
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/orm/core.py", line 2278, in __get__
value = attr.get(obj)
File "/Users/jwag/fs/py3.7env/lib/python3.7/site-packages/pony/orm/core.py", line 2286, in get
vals = obj._vals_
AttributeError: _vals_
Since Pony is using meta-programming - I can't really figure out where/why it is using hash and why defining it confuses it so much.
Any thoughts?

Answer 1

You may have an '#classmethod' decorator before your mixin class methods.
class RoleMixin:
#classmethod
def __hash__(cls):
return hash(cls.name)
#classmethod
def __eq__(cls, other):
return cls.name == other or cls.name == getattr(other, "name", None)
#classmethod
def get_permissions(cls):
if cls.permissions:
return cls.permissions
return set()