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An app that is forced to the top of the list in ``INSTALLED_APPS``
for the purpose of hooking into Django's ``class_prepared`` signal
and adding custom fields as defined by the ``EXTRA_MODEL_FIELDS``
setting. Also patches ```` to use
``LazyAdminSite`` that defers certains register/unregister calls
until ``admin.autodiscover`` to avoid some timing issues around
custom fields not being available when custom admin classes are
from __future__ import unicode_literals
from collections import defaultdict
from django import VERSION as DJANGO_VERSION
from django.apps import apps
from django.conf import settings
from django.contrib import admin
from django.core.exceptions import ImproperlyConfigured
from django.db.models.signals import class_prepared
from mezzanine.boot.lazy_admin import LazyAdminSite
from mezzanine.utils.importing import import_dotted_path
def parse_field_path(field_path):
Take a path to a field like "mezzanine.pages.models.Page.feature_image"
and return a model key, which is a tuple of the form ('pages', 'page'),
and a field name, e.g. "feature_image".
model_path, field_name = field_path.rsplit(".", 1)
app_name, model_name = model_path.split('.models.')
_, app_label = app_name.rsplit('.', 1)
return (app_label, model_name.lower()), field_name
def import_field(field_classpath):
Imports a field by its dotted class path, prepending "django.db.models"
to raw class names and raising an exception if the import fails.
if '.' in field_classpath:
fully_qualified = field_classpath
fully_qualified = "django.db.models.%s" % field_classpath
return import_dotted_path(fully_qualified)
except ImportError:
raise ImproperlyConfigured("The EXTRA_MODEL_FIELDS setting contains "
"the field '%s' which could not be "
"imported." % field_classpath)
def parse_extra_model_fields(extra_model_fields):
Parses the value of EXTRA_MODEL_FIELDS, grouping the entries by model
and instantiating the extra fields. Returns a sequence of tuples of
the form (model_key, fields) where model_key is a pair of app_label,
model_name and fields is a list of (field_name, field_instance) pairs.
fields = defaultdict(list)
for entry in extra_model_fields:
model_key, field_name = parse_field_path(entry[0])
field_class = import_field(entry[1])
field_args, field_kwargs = entry[2:]
field = field_class(*field_args, **field_kwargs)
except TypeError as e:
raise ImproperlyConfigured(
"The EXTRA_MODEL_FIELDS setting contains arguments for the "
"field '%s' which could not be applied: %s" % (entry[1], e))
fields[model_key].append((field_name, field))
return fields
fields = parse_extra_model_fields(getattr(settings, "EXTRA_MODEL_FIELDS", []))
def add_extra_model_fields(sender, **kwargs):
Injects custom fields onto the given sender model as defined
by the ``EXTRA_MODEL_FIELDS`` setting. This is a closure over
the "fields" variable.
model_key = sender._meta.app_label, sender._meta.model_name
for field_name, field in fields.get(model_key, {}):
field.contribute_to_class(sender, field_name)
if DJANGO_VERSION < (1, 9):
if fields:
for model_key in fields:
apps.lazy_model_operation(add_extra_model_fields, model_key)
# Override with LazyAdminSite. It must
# be bound to a separate name (admin_site) for access in autodiscover
# below.
admin_site = LazyAdminSite() = admin_site
django_autodiscover = admin.autodiscover
def autodiscover(*args, **kwargs):
Replaces django's original autodiscover to add a call to
LazyAdminSite's lazy_registration.
django_autodiscover(*args, **kwargs)
admin.autodiscover = autodiscover
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