Django - disable one of system checks

Question

Is it possible to permamently disable only ONE (not all) of the system checks (for example E301)? Is it possible to change project settings.py to skip this system check for all ./manage.py commands?

Answer 1

Yes you can use SILENCED_SYSTEM_CHECKS to silence specific checks e.g.

settings.py

SILENCED_SYSTEM_CHECKS = ["models.W001"]

Answer 2

To disable a check (or many checks) under certain conditions only, you can create a settings constant, and in this case I am getting the information from an environment variable:

# Disable checks, i.e. for build process
DISABLE_CHECKS = os.getenv('DISABLE_CHECKS') in ('1', 1, True)
if DISABLE_CHECKS:
    SILENCED_SYSTEM_CHECKS = ['content_services.E001', 'content_services.E002']

The name of the check is the id you assign it in your error message. Here is a sample check:

def check_cache_connectivity(app_configs, **kwargs):
    """
    Check cache
    :param app_configs:
    :param kwargs:
    :return:
    """
    errors = []

    cache_settings = settings.CACHES.keys()
    for cur_cache in cache_settings:
        try:
            key = 'check_cache_connectivity_{}'.format(cur_cache)
            caches[cur_cache].set(key, 'connectivity_ok', 30)
            value = caches[cur_cache].get(key)
            print("Cache '{}' connection ok, key '{}', value '{}'".format(cur_cache, key, value))
        except Exception as e:
            msg = "ERROR: Cache {} looks to be down. {}".format(cur_cache, e)
            print(msg)
            logging.exception(msg)
            errors.append(
                Error(
                    msg,
                    hint='Unable to connect to cache {}. {}'.format(cur_cache, e),
                    obj='CACHES.{}'.format(cur_cache),
                    id='content_services.E002',
                )
            )
    return errors

The way I initiate these checks are in my apps.py for the particular app i.e.:

from django.apps import AppConfig
from django.core import checks
from common_checks import check_db_connectivity
from common_checks import check_cache_connectivity


class ContentAppConfig(AppConfig):
    name = 'content_app'

    def ready(self):
        super(ContentAppConfig, self).ready()
        checks.register(checks.Tags.compatibility)(check_cache_connectivity)

In my apps __init__.py I also set the default app config:

default_app_config = 'content_app.apps.ContentAppConfig'

Hope it helps!

UPDATE: Some manage.py commands will run checks regardless of the SILENCED_SYSTEM_CHECKS value. For this I have a special workaround:

def check_cache_connectivity(app_configs, **kwargs):
    """
    Check cache
    :param app_configs:
    :param kwargs:
    :return:
    """
    errors = []

    # Short circuit here, checks still ran by manage.py cmds regardless of SILENCED_SYSTEM_CHECKS
    if settings.DISABLE_CHECKS:
        return errors

    cache_settings = settings.CACHES.keys()
    for cur_cache in cache_settings:
        try:
            key = 'check_cache_connectivity_{}'.format(cur_cache)
            caches[cur_cache].set(key, 'connectivity_ok', 30)
            value = caches[cur_cache].get(key)
            print("Cache '{}' connection ok, key '{}', value '{}'".format(cur_cache, key, value))
        except Exception as e:
            msg = "ERROR: Cache {} looks to be down. {}".format(cur_cache, e)
            print(msg)
            logging.exception(msg)
            errors.append(
                Error(
                    msg,
                    hint="Unable to connect to cache {}, set as {}. {}"
                         "".format(cur_cache, settings.CACHES[cur_cache], e),
                    obj='CACHES.{}'.format(cur_cache),
                    id='content_services.E002',
                )
            )
    return errors