Specifying db_default on FileField causes crash on instance save

[David Sanders]

I guess there's the existential question: "Does db_default make sense with FileField/ImageField?" Perhaps, as long as there's a file at the path defined by the db_default expression? 🤔

In any case when defined with a FileField, the presence of DatabaseDefault as the field's value causes a crash:

Given the model:

class Foo(models.Model):
    bar = models.FileField(db_default="path/to/file.txt")

We get AttributeError exceptions when attempting to create an instance:

>>> Foo.objects.create()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/path/to/django/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/query.py", line 660, in create
    obj.save(force_insert=True, using=self.db)
  File "/path/to/django/django/db/models/base.py", line 891, in save
    self.save_base(
  File "/path/to/django/django/db/models/base.py", line 997, in save_base
    updated = self._save_table(
              ^^^^^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/base.py", line 1160, in _save_table
    results = self._do_insert(
              ^^^^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/base.py", line 1201, in _do_insert
    return manager._insert(
           ^^^^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/query.py", line 1828, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/sql/compiler.py", line 1847, in execute_sql
    for sql, params in self.as_sql():
                       ^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/sql/compiler.py", line 1770, in as_sql
    value_rows = [
                 ^
  File "/path/to/django/django/db/models/sql/compiler.py", line 1771, in <listcomp>
    [
  File "/path/to/django/django/db/models/sql/compiler.py", line 1772, in <listcomp>
    self.prepare_value(field, self.pre_save_val(field, obj))
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/sql/compiler.py", line 1720, in pre_save_val
    return field.pre_save(obj, add=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/path/to/django/django/db/models/fields/files.py", line 320, in pre_save
    if file.name is None and file._file is not None:
       ^^^^^^^^^
AttributeError: 'DatabaseDefault' object has no attribute 'name'

[Sarah Boyce]

I feel like the behavior should mimic default here - accepting

[Mohammad Salehi]

Hi, I tested this issue and it indeed exists. It can be resolved by initiating self.name to None in init, and that's it
I would send a PR to address this alongside a test, if you are ok.

[Sarah Boyce]

Replying to Mohammad Salehi:

Hi, I tested this issue and it indeed exists. It can be resolved by initiating self.name to None in init, and that's it
I would send a PR to address this alongside a test, if you are ok.

That doesn't sound right
I've opened a PR

[GitHub <noreply@…>]

In 8deb6bb1:

Fixed #35657 -- Made FileField handle db_default values.

[Natalia <124304+nessita@…>]

In 2ba4f4b0:

[5.1.x] Fixed #35657 -- Made FileField handle db_default values.

Backport of 8deb6bb1fc427762d56646bf7306cbd11fb5bb68 from main.

[Natalia <124304+nessita@…>]

In d7f9554:

[5.0.x] Fixed #35657 -- Made FileField handle db_default values.

Backport of 8deb6bb1fc427762d56646bf7306cbd11fb5bb68 from main.