Django FileField default callable problem

README.md

FileField callable default problem

How to reproduce:

• create a virtualenv and activate it. Install Django (pip install django)

• create a new testdefault project : django-admin startproject testdefault

• copy the gist file into the testdefault folder (i.e. files admin.py, models.py, settings.py)

• run the following commands:

  $ python manage.py migrate
  $ python manage.py createsuperuser
  $ python manage.py runserver
  

• navigate to http://localhost:8000/admin/

• when creating "Test objects" we have the error 'function' object has no attribute '_committed' in django/db/models/fields/files.py in pre_save, line 313

• when creating "Test object strs" no problem.

• the only difference between them is the teh value of the default attribute of their FileField field. One (TestObjectStr) is a simple string, the other (TestObject) is a callable returning the same string.

• To note: this bug does not appear when directly creating objects in code. It seems related to the form management. You can test it by running a django shell. This runs without problem, with the expected default value:

  $ python manage.py shell
    >>> from testdefault import models
    >>> models.TestObject.objects.create()
  

admin.py

from django.contrib import admin

from .models import TestObject, TestObjectStr

admin.site.register(TestObject)
admin.site.register(TestObjectStr)

models.py

from django.db import models

def get_test_object_default():
    return "path/to/some/file"

class TestObject(models.Model):
    pub_file = models.FileField(default=get_test_object_default)

class TestObjectStr(models.Model):
    pub_file = models.FileField(default="path/to/some/file")

settings.py

"""
Django settings for testdefault project.

Generated by 'django-admin startproject' using Django 1.8.1.

For more information on this file, see
https://docs.djangoproject.com/en/1.8/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/1.8/ref/settings/
"""

# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
import os

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/1.8/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = 'nkd^!*%vhu)e!_c1^&6m1-kfhz9upewo-qnqurh_w)y01!e^b2'

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = []


# Application definition

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'testdefault'
)

MIDDLEWARE_CLASSES = (
    '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',
)

ROOT_URLCONF = 'testdefault.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'testdefault.wsgi.application'


# Database
# https://docs.djangoproject.com/en/1.8/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}


# Internationalization
# https://docs.djangoproject.com/en/1.8/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_L10N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/1.8/howto/static-files/

STATIC_URL = '/static/'