id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
30238	Exception when saving model created with string for DateField	Mitchell Harvey	nobody	"If you instantiate a new model object with a keyword argument value for a DateField given a string, an exception is thrown when the object is saved.  However, the model is saved anyways.

Example Error:
AttributeError: 'str' object has no attribute 'isoformat'

Call Stack:
{{{
File ""REDACTED"", line 746, in migrate_remote_unactive_driver
    local_driver.save()
  File ""REDACTED"", line 171, in save
    super(Driver, self).save(*args, **kwargs)
  File ""REDACTED/env/lib/python3.6/site-packages/django/db/models/base.py"", line 729, in save
    force_update=force_update, update_fields=update_fields)
  File ""REDACTED/env/lib/python3.6/site-packages/django/db/models/base.py"", line 769, in save_base
    update_fields=update_fields, raw=raw, using=using,
  File ""REDACTED/env/lib/python3.6/site-packages/django/dispatch/dispatcher.py"", line 178, in send
    for receiver in self._live_receivers(sender)
  File ""REDACTED/env/lib/python3.6/site-packages/django/dispatch/dispatcher.py"", line 178, in <listcomp>
    for receiver in self._live_receivers(sender)
  File ""REDACTED"", line 12, in create_launch_list
    serialized_obj = serializers.serialize('json', [instance])
  File ""REDACTED/env/lib/python3.6/site-packages/django/core/serializers/__init__.py"", line 128, in serialize
    s.serialize(queryset, **options)
  File ""REDACTED/env/lib/python3.6/site-packages/django/core/serializers/base.py"", line 89, in serialize
    self.handle_field(obj, field)
  File ""REDACTED/env/lib/python3.6/site-packages/django/core/serializers/python.py"", line 51, in handle_field
    self._current[field.name] = self._value_from_field(obj, field)
  File ""REDACTED/env/lib/python3.6/site-packages/django/core/serializers/python.py"", line 47, in _value_from_field
    return value if is_protected_type(value) else field.value_to_string(obj)
  File ""REDACTED/env/lib/python3.6/site-packages/django/db/models/fields/__init__.py"", line 1281, in value_to_string
    return '' if val is None else val.isoformat()
AttributeError: 'str' object has no attribute 'isoformat'

}}}

django/db/models/fields/__init__.py 
 
value_to_string(self, obj)

Presumes that obj is not of type string already.  

To Reproduce:

Create a model with a a field of type 'DateField'

{{{
class MyModel(models.Model):

   worthless_field = models.DateField(null=True, blank=True)
}}}

Instantiate and save an object of type 'MyModel' in a view.py:

{{{
my_model_args = { 'worthless_field' : '2019-02-07'}
myExceptionalModel = MyModel( **my_model_args)

# Exception thrown here
myExceptionalModel.save()

# Although, model is actually saved.
}}}


Please check if the value is a valid datetime string already before attempting to convert it to a string.  It would be nice if a model was not saved when an exception is thrown.  

Or do whatever you like, I have to work around it anyways.

Good luck, love Django, great job guys!  




"	Bug	closed	Database layer (models, ORM)	2.1	Normal	invalid			Unreviewed	0	0	0	0	1	0