django/apps/config.py
import inspect
import os
from importlib import import_module
from django.core.exceptions import ImproperlyConfigured
from django.utils.functional import cached_property
from django.utils.module_loading import import_string, module_has_submodule
APPS_MODULE_NAME = "apps"
MODELS_MODULE_NAME = "models"
class AppConfig:
"""Class representing a Django application and its configuration."""
def __init__(self, app_name, app_module):
# Full Python path to the application e.g. 'django.contrib.admin'.
self.name = app_name
# Root module for the application e.g. <module 'django.contrib.admin'
# from 'django/contrib/admin/__init__.py'>.
self.module = app_module
# Reference to the Apps registry that holds this AppConfig. Set by the
# registry when it registers the AppConfig instance.
self.apps = None
# The following attributes could be defined at the class level in a
# subclass, hence the test-and-set pattern.
# Last component of the Python path to the application e.g. 'admin'.
# This value must be unique across a Django project.
if not hasattr(self, "label"):
self.label = app_name.rpartition(".")[2]
if not self.label.isidentifier():
raise ImproperlyConfigured(
"The app label '%s' is not a valid Python identifier." % self.label
)
# Human-readable name for the application e.g. "Admin".
if not hasattr(self, "verbose_name"):
self.verbose_name = self.label.title()
# Filesystem path to the application directory e.g.
# '/path/to/django/contrib/admin'.
if not hasattr(self, "path"):
self.path = self._path_from_module(app_module)
# Module containing models e.g. <module 'django.contrib.admin.models'
# from 'django/contrib/admin/models.py'>. Set by import_models().
# None if the application doesn't have a models module.
self.models_module = None
# Mapping of lowercase model names to model classes. Initially set to
# None to prevent accidental access before import_models() runs.
self.models = None
def __repr__(self):
return "<%s: %s>" % (self.__class__.__name__, self.label)
@cached_property
def default_auto_field(self):
from django.conf import settings
return settings.DEFAULT_AUTO_FIELD
@property
def _is_default_auto_field_overridden(self):
return self.__class__.default_auto_field is not AppConfig.default_auto_field
def _path_from_module(self, module):
"""Attempt to determine app's filesystem path from its module."""
# See #21874 for extended discussion of the behavior of this method in
# various cases.
# Convert to list because __path__ may not support indexing.
paths = list(getattr(module, "__path__", []))
if len(paths) != 1:
filename = getattr(module, "__file__", None)
if filename is not None:
paths = [os.path.dirname(filename)]
else:
# For unknown reasons, sometimes the list returned by __path__
# contains duplicates that must be removed (#25246).
paths = list(set(paths))
if len(paths) > 1:
raise ImproperlyConfigured(
"The app module %r has multiple filesystem locations (%r); "
"you must configure this app with an AppConfig subclass "
"with a 'path' class attribute." % (module, paths)
)
elif not paths:
raise ImproperlyConfigured(
"The app module %r has no filesystem location, "
"you must configure this app with an AppConfig subclass "
"with a 'path' class attribute." % module
)
return paths[0]
@classmethod
def create(cls, entry):
"""
Factory that creates an app config from an entry in INSTALLED_APPS.
"""
# create() eventually returns app_config_class(app_name, app_module).
app_config_class = None
app_name = None
app_module = None
# If import_module succeeds, entry points to the app module.
try:
app_module = import_module(entry)
except Exception:
pass
else:
# If app_module has an apps submodule that defines a single
# AppConfig subclass, use it automatically.
# To prevent this, an AppConfig subclass can declare a class
# variable default = False.
# If the apps module defines more than one AppConfig subclass,
# the default one can declare default = True.
if module_has_submodule(app_module, APPS_MODULE_NAME):
mod_path = "%s.%s" % (entry, APPS_MODULE_NAME)
mod = import_module(mod_path)
# Check if there's exactly one AppConfig candidate,
# excluding those that explicitly define default = False.
app_configs = [
(name, candidate)
for name, candidate in inspect.getmembers(mod, inspect.isclass)
if (
issubclass(candidate, cls)
and candidate is not cls
and getattr(candidate, "default", True)
)
]
if len(app_configs) == 1:
app_config_class = app_configs[0][1]
else:
# Check if there's exactly one AppConfig subclass,
# among those that explicitly define default = True.
app_configs = [
(name, candidate)
for name, candidate in app_configs
if getattr(candidate, "default", False)
]
if len(app_configs) > 1:
candidates = [repr(name) for name, _ in app_configs]
raise RuntimeError(
"%r declares more than one default AppConfig: "
"%s." % (mod_path, ", ".join(candidates))
)
elif len(app_configs) == 1:
app_config_class = app_configs[0][1]
# Use the default app config class if we didn't find anything.
if app_config_class is None:
app_config_class = cls
app_name = entry
# If import_string succeeds, entry is an app config class.
if app_config_class is None:
try:
app_config_class = import_string(entry)
except Exception:
pass
# If both import_module and import_string failed, it means that entry
# doesn't have a valid value.
if app_module is None and app_config_class is None:
# If the last component of entry starts with an uppercase letter,
# then it was likely intended to be an app config class; if not,
# an app module. Provide a nice error message in both cases.
mod_path, _, cls_name = entry.rpartition(".")
if mod_path and cls_name[0].isupper():
# We could simply re-trigger the string import exception, but
# we're going the extra mile and providing a better error
# message for typos in INSTALLED_APPS.
# This may raise ImportError, which is the best exception
# possible if the module at mod_path cannot be imported.
mod = import_module(mod_path)
candidates = [
repr(name)
for name, candidate in inspect.getmembers(mod, inspect.isclass)
if issubclass(candidate, cls) and candidate is not cls
]
msg = "Module '%s' does not contain a '%s' class." % (
mod_path,
cls_name,
)
if candidates:
msg += " Choices are: %s." % ", ".join(candidates)
raise ImportError(msg)
else:
# Re-trigger the module import exception.
import_module(entry)
# Check for obvious errors. (This check prevents duck typing, but
# it could be removed if it became a problem in practice.)
if not issubclass(app_config_class, AppConfig):
raise ImproperlyConfigured("'%s' isn't a subclass of AppConfig." % entry)
# Obtain app name here rather than in AppClass.__init__ to keep
# all error checking for entries in INSTALLED_APPS in one place.
if app_name is None:
try:
app_name = app_config_class.name
except AttributeError:
raise ImproperlyConfigured("'%s' must supply a name attribute." % entry)
# Ensure app_name points to a valid module.
try:
app_module = import_module(app_name)
except ImportError:
raise ImproperlyConfigured(
"Cannot import '%s'. Check that '%s.%s.name' is correct."
% (
app_name,
app_config_class.__module__,
app_config_class.__qualname__,
)
)
# Entry is a path to an app config class.
return app_config_class(app_name, app_module)
def get_model(self, model_name, require_ready=True):
"""
Return the model with the given case-insensitive model_name.
Raise LookupError if no model exists with this name.
"""
if require_ready:
self.apps.check_models_ready()
else:
self.apps.check_apps_ready()
try:
return self.models[model_name.lower()]
except KeyError:
raise LookupError(
"App '%s' doesn't have a '%s' model." % (self.label, model_name)
)
def get_models(self, include_auto_created=False, include_swapped=False):
"""
Return an iterable of models.
By default, the following models aren't included:
- auto-created models for many-to-many relations without
an explicit intermediate table,
- models that have been swapped out.
Set the corresponding keyword argument to True to include such models.
Keyword arguments aren't documented; they're a private API.
"""
self.apps.check_models_ready()
for model in self.models.values():
if model._meta.auto_created and not include_auto_created:
continue
if model._meta.swapped and not include_swapped:
continue
yield model
def import_models(self):
# Dictionary of models for this app, primarily maintained in the
# 'all_models' attribute of the Apps this AppConfig is attached to.
self.models = self.apps.all_models[self.label]
if module_has_submodule(self.module, MODELS_MODULE_NAME):
models_module_name = "%s.%s" % (self.name, MODELS_MODULE_NAME)
self.models_module = import_module(models_module_name)
def ready(self):
"""
Override this method in subclasses to run code when Django starts.
"""