Excluding attributes on an attrs model from unstructuring breaks auto unstructuring #169
Description
- cattrs version: 1.8.0
- Python version: 3.9.2
- Operating System: OSX - Big Sur 11.5.2
Description
I have a field on an attrs model that I want excluded when unstructuring. When registering an unstructure hook using make_dict_unstructure_fn and field=override(Skip=True) (as read in the documentation) the other unstructure hooks aren't being triggered (UUID, nested models, etc). The same issue happens if the example using register_unstructure_hook_factory is used instead.
What I Did
Sample program to demonstrate the issue. Running json.dumps on the unstructured Breaks will break complaining that Object of type UUID is not JSON serializable (or if the ID is commented out then Object of type Nested), whereas it works properly on Works
from __future__ import annotations
import json
from typing import Optional
from uuid import UUID, uuid4
import attr
from cattr import GenConverter
from cattr.gen import make_dict_unstructure_fn, override
@attr.s(auto_attribs=True, slots=True, frozen=True)
class Nested:
nested_string: Optional[str] = attr.ib(factory=lambda: str(uuid4()))
@attr.s(auto_attribs=True, slots=True, frozen=True)
class Works(object):
id: UUID = attr.ib(factory=uuid4)
nested: Nested = attr.ib(factory=Nested)
@attr.s(auto_attribs=True, slots=True, frozen=True)
class Breaks(object):
id: UUID = attr.ib(factory=uuid4)
exclude_me: str = attr.ib(factory=lambda: str(uuid4()))
nested: Nested = attr.ib(factory=Nested)
def _gen_conv() -> GenConverter:
_conv = GenConverter()
_conv.register_unstructure_hook(frozenset, lambda v: list(v))
_conv.register_unstructure_hook(UUID, lambda v: str(v))
# This handles skipping `exclude_me` properly, but other nested attr classes don't get properly unstructured
_conv.register_unstructure_hook(Breaks, make_dict_unstructure_fn(Breaks, _conv, exclude_me=override(omit=True)))
return _conv
def unstructure_breaks(breaks):
doesnt_break = conv.unstructure(breaks)
doesnt_break.pop("exclude_me", None)
return doesnt_break
if __name__ == '__main__':
conv = _gen_conv()
print(json.dumps(conv.unstructure(Works())))
print(json.dumps(conv.unstructure(Breaks()))) # Breaks because it can't serialize UUID/Nested❯ python cattr_poc.py
{"id": "dbab1954-5338-40f1-a9f8-9ba8ec5a280d", "nested": {"nested_string": "e0317c43-c06e-44c8-b6df-fd992649a57c"}}
Traceback (most recent call last):
File "/Users/jason/dev/cattr_poc.py", line 50, in <module>
print(json.dumps(unstructure_breaks(Breaks())))
File "/Users/jason/.pyenv/versions/3.9.2/lib/python3.9/json/__init__.py", line 231, in dumps
return _default_encoder.encode(obj)
File "/Users/jason/.pyenv/versions/3.9.2/lib/python3.9/json/encoder.py", line 199, in encode
chunks = self.iterencode(o, _one_shot=True)
File "/Users/jason/.pyenv/versions/3.9.2/lib/python3.9/json/encoder.py", line 257, in iterencode
return _iterencode(o, 0)
File "/Users/jason/.pyenv/versions/3.9.2/lib/python3.9/json/encoder.py", line 179, in default
raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type UUID is not JSON serializableWhat I would expect
I'm looking for a good way to exclude one or more attributes from unstructuring an attrs model without needing to wrap them in a function like this:
def unstructure_breaks(breaks):
doesnt_break = conv.unstructure(breaks)
doesnt_break.pop("exclude_me", None)
return doesnt_break