FileField with callable default raise error with forms

[Haussonne Yves-Marie]

Hello,

When a FileField has a callable default value, the following error is raised when a new object is created using a form and no value is provided for the field:

'function' object has no attribute '_committed' in db/models/fields/files.py in pre_save, line 316

This bug can be reproduced with the content of the following gist : ​https://gist.github.com/ymph/cd2b684f3f2f38a680d5 and by following the instruction in the README.

The problem does not appear when creating the object without forms.

I was able to naively "correct" the problem by adding the following lines in the file db/models/fields/files.py, line 194 in FieldFile.__get__:

        if callable(file):
            file = file()

here is a complete traceback:

Environment:


Request Method: POST
Request URL: http://localhost:8000/admin/testdefault/testobject/add/

Django Version: 1.8.1
Python Version: 2.7.6
Installed Applications:
('django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'testdefault')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'django.middleware.security.SecurityMiddleware')


Traceback:
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  132.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/contrib/admin/options.py" in wrapper
  616.                 return self.admin_site.admin_view(view)(*args, **kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/utils/decorators.py" in _wrapped_view
  110.                     response = view_func(request, *args, **kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
  57.         response = view_func(request, *args, **kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/contrib/admin/sites.py" in inner
  233.             return view(request, *args, **kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/contrib/admin/options.py" in add_view
  1516.         return self.changeform_view(request, None, form_url, extra_context)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/utils/decorators.py" in _wrapper
  34.             return bound_func(*args, **kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/utils/decorators.py" in _wrapped_view
  110.                     response = view_func(request, *args, **kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/utils/decorators.py" in bound_func
  30.                 return func.__get__(self, type(self))(*args2, **kwargs2)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/utils/decorators.py" in inner
  145.                     return func(*args, **kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/contrib/admin/options.py" in changeform_view
  1467.                 self.save_model(request, new_object, form, not add)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/contrib/admin/options.py" in save_model
  1078.         obj.save()
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/base.py" in save
  710.                        force_update=force_update, update_fields=update_fields)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/base.py" in save_base
  738.             updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/base.py" in _save_table
  822.             result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/base.py" in _do_insert
  861.                                using=using, raw=raw)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/manager.py" in manager_method
  127.                 return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/query.py" in _insert
  920.         return query.get_compiler(using=using).execute_sql(return_id)
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/sql/compiler.py" in execute_sql
  970.             for sql, params in self.as_sql():
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/sql/compiler.py" in as_sql
  928.                 for obj in self.query.objs
File "/Users/ymh/dev/venvs/testdefault/lib/python2.7/site-packages/django/db/models/fields/files.py" in pre_save
  316.         if file and not file._committed:

Exception Type: AttributeError at /admin/testdefault/testobject/add/
Exception Value: 'function' object has no attribute '_committed'

regards.