DateTimeField deepcopy causes error introduced in 1.2.1.

The library moved from a shallow copy to a deep copy while moving to 1.2.1 from 1.2. This caused my project’s tests to fail when saving a model with a DateTimeField where auto_now=True is set. Haven’t done any testing on whether this is the cause (that DateTimeField is the cause though, not sure whether that attribute is). I will try to come up with some tests the coming days as it’s very late as I post this. But what was the reason for changing the shallow copy to a deep copy? Changing the deep copy to a shallow copy resolves the issue.

This is the exact field that’s causing the issue:

last_modified = models.DateTimeField(
    auto_now=True,
    verbose_name=_('...'),
    help_text=_('...')
)

The traceback:

  File "/Users/Andreas/Development/Python/SomeProjectYay/project/app/models.py", line 218, in save
    super(SomeModel, self).save(*args, **kwargs)
  File "/Users/Andreas/.pyenv/versions/SomeProjectYay/lib/python3.5/site-packages/django/db/models/base.py", line 708, in save
    force_update=force_update, update_fields=update_fields)
  File "/Users/Andreas/.pyenv/versions/SomeProjectYay/lib/python3.5/site-packages/django/db/models/base.py", line 745, in save_base
    update_fields=update_fields, raw=raw, using=using)
  File "/Users/Andreas/.pyenv/versions/SomeProjectYay/lib/python3.5/site-packages/django/dispatch/dispatcher.py", line 192, in send
    response = receiver(signal=self, sender=sender, **named)
  File "/Users/Andreas/.pyenv/versions/SomeProjectYay/lib/python3.5/site-packages/dirtyfields/dirtyfields.py", line 124, in reset_state
    new_state = instance._as_dict(check_relationship=True)
  File "/Users/Andreas/.pyenv/versions/SomeProjectYay/lib/python3.5/site-packages/dirtyfields/dirtyfields.py", line 69, in _as_dict
    all_field[field.name] = deepcopy(field_value)
  File "/Users/Andreas/.pyenv/versions/3.5.2/lib/python3.5/copy.py", line 182, in deepcopy
    y = _reconstruct(x, rv, 1, memo)
  File "/Users/Andreas/.pyenv/versions/3.5.2/lib/python3.5/copy.py", line 291, in _reconstruct
    args = deepcopy(args, memo)
  File "/Users/Andreas/.pyenv/versions/3.5.2/lib/python3.5/copy.py", line 155, in deepcopy
    y = copier(x, memo)
  File "/Users/Andreas/.pyenv/versions/3.5.2/lib/python3.5/copy.py", line 223, in _deepcopy_tuple
    y = [deepcopy(a, memo) for a in x]
  File "/Users/Andreas/.pyenv/versions/3.5.2/lib/python3.5/copy.py", line 223, in <listcomp>
    y = [deepcopy(a, memo) for a in x]
  File "/Users/Andreas/.pyenv/versions/3.5.2/lib/python3.5/copy.py", line 182, in deepcopy
    y = _reconstruct(x, rv, 1, memo)
  File "/Users/Andreas/.pyenv/versions/3.5.2/lib/python3.5/copy.py", line 292, in _reconstruct
    y = callable(*args)
TypeError: __init__() missing 2 required positional arguments: 'tz' and 'transition_type'

Python version: 3.5.2. Django version: 1.9.12.

[AndreasBackx]

@romgar I’ll try to look at the issue more in detail the coming days. Feel free to ping me to remind me if it has been a while though.

[AndreasBackx]

@romgar I found the culprit and referenced it. Perhaps this could be prevented in the future by not deepcopying primitive types and other “protected types” as Django describes it in their serializers? https://github.com/django/django/blob/master/django/core/serializers/python.py#L44-L47