"Utilities for loading models and the modules that contain them." from django.conf import settings from django.core.exceptions import ImproperlyConfigured from django.utils.datastructures import SortedDict from django.utils.importlib import import_module from django.utils.module_loading import module_has_submodule from django.utils._os import upath from django.utils import six import imp import sys import os __all__ = ('get_apps', 'get_app', 'get_models', 'get_model', 'register_models', 'load_app', 'app_cache_ready') class UnavailableApp(Exception): pass class AppCache(object): """ A cache that stores installed applications and their models. Used to provide reverse-relations and for app introspection (e.g. admin). """ # Use the Borg pattern to share state between all instances. Details at # http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66531. __shared_state = dict( # Keys of app_store are the model modules for each application. app_store=SortedDict(), # Mapping of installed app_labels to model modules for that app. app_labels={}, # Mapping of app_labels to a dictionary of model names to model code. # May contain apps that are not installed. app_models=SortedDict(), # Mapping of app_labels to errors raised when trying to import the app. app_errors={}, # -- Everything below here is only used when populating the cache -- loaded=False, handled=set(), postponed=[], nesting_level=0, _get_models_cache={}, available_apps=None, ) def __init__(self): self.__dict__ = self.__shared_state def _populate(self): """ Fill in all the cache information. This method is threadsafe, in the sense that every caller will see the same state upon return, and if the cache is already initialised, it does no work. """ if self.loaded: return # Note that we want to use the import lock here - the app loading is # in many cases initiated implicitly by importing, and thus it is # possible to end up in deadlock when one thread initiates loading # without holding the importer lock and another thread then tries to # import something which also launches the app loading. For details of # this situation see #18251. imp.acquire_lock() try: if self.loaded: return for app_name in settings.INSTALLED_APPS: if app_name in self.handled: continue self.load_app(app_name, True) if not self.nesting_level: for app_name in self.postponed: self.load_app(app_name) self.loaded = True finally: imp.release_lock() def _label_for(self, app_mod): """ Return app_label for given models module. """ return app_mod.__name__.split('.')[-2] def load_app(self, app_name, can_postpone=False): """ Loads the app with the provided fully qualified name, and returns the model module. """ self.handled.add(app_name) self.nesting_level += 1 app_module = import_module(app_name) try: models = import_module('%s.models' % app_name) except ImportError: self.nesting_level -= 1 # If the app doesn't have a models module, we can just ignore the # ImportError and return no models for it. if not module_has_submodule(app_module, 'models'): return None # But if the app does have a models module, we need to figure out # whether to suppress or propagate the error. If can_postpone is # True then it may be that the package is still being imported by # Python and the models module isn't available yet. So we add the # app to the postponed list and we'll try it again after all the # recursion has finished (in populate). If can_postpone is False # then it's time to raise the ImportError. else: if can_postpone: self.postponed.append(app_name) return None else: raise self.nesting_level -= 1 if models not in self.app_store: self.app_store[models] = len(self.app_store) self.app_labels[self._label_for(models)] = models return models def app_cache_ready(self): """ Returns true if the model cache is fully populated. Useful for code that wants to cache the results of get_models() for themselves once it is safe to do so. """ return self.loaded def get_apps(self): """ Returns a list of all installed modules that contain models. """ self._populate() apps = self.app_store.items() if self.available_apps is not None: apps = [elt for elt in apps if self._label_for(elt[0]) in self.available_apps] # Ensure the returned list is always in the same order (with new apps # added at the end). This avoids unstable ordering on the admin app # list page, for example. apps = sorted(apps, key=lambda elt: elt[1]) return [elt[0] for elt in apps] def get_app_paths(self): """ Returns a list of paths to all installed apps. Useful for discovering files at conventional locations inside apps (static files, templates, etc.) """ self._populate() app_paths = [] for app in self.get_apps(): if hasattr(app, '__path__'): # models/__init__.py package app_paths.extend([upath(path) for path in app.__path__]) else: # models.py module app_paths.append(upath(app.__file__)) return app_paths def get_app(self, app_label, emptyOK=False): """ Returns the module containing the models for the given app_label. Returns None if the app has no models in it and emptyOK is True. Raises UnavailableApp when set_available_apps() in in effect and doesn't include app_label. """ self._populate() imp.acquire_lock() try: for app_name in settings.INSTALLED_APPS: if app_label == app_name.split('.')[-1]: mod = self.load_app(app_name, False) if mod is None and not emptyOK: raise ImproperlyConfigured("App with label %s is missing a models.py module." % app_label) if self.available_apps is not None and app_label not in self.available_apps: raise UnavailableApp("App with label %s isn't available." % app_label) return mod raise ImproperlyConfigured("App with label %s could not be found" % app_label) finally: imp.release_lock() def get_app_errors(self): "Returns the map of known problems with the INSTALLED_APPS." self._populate() return self.app_errors def get_models(self, app_mod=None, include_auto_created=False, include_deferred=False, only_installed=True, include_swapped=False): """ Given a module containing models, returns a list of the models. Otherwise returns a list of all installed models. By default, auto-created models (i.e., m2m models without an explicit intermediate table) are not included. However, if you specify include_auto_created=True, they will be. By default, models created to satisfy deferred attribute queries are *not* included in the list of models. However, if you specify include_deferred, they will be. By default, models that aren't part of installed apps will *not* be included in the list of models. However, if you specify only_installed=False, they will be. By default, models that have been swapped out will *not* be included in the list of models. However, if you specify include_swapped, they will be. """ cache_key = (app_mod, include_auto_created, include_deferred, only_installed, include_swapped) model_list = None try: model_list = self._get_models_cache[cache_key] if self.available_apps is not None and only_installed: model_list = [m for m in model_list if m._meta.app_label in self.available_apps] return model_list except KeyError: pass self._populate() if app_mod: if app_mod in self.app_store: app_list = [self.app_models.get(self._label_for(app_mod), SortedDict())] else: app_list = [] else: if only_installed: app_list = [self.app_models.get(app_label, SortedDict()) for app_label in six.iterkeys(self.app_labels)] else: app_list = six.itervalues(self.app_models) model_list = [] for app in app_list: model_list.extend( model for model in app.values() if ((not model._deferred or include_deferred) and (not model._meta.auto_created or include_auto_created) and (not model._meta.swapped or include_swapped)) ) self._get_models_cache[cache_key] = model_list if self.available_apps is not None and only_installed: model_list = [m for m in model_list if m._meta.app_label in self.available_apps] return model_list def get_model(self, app_label, model_name, seed_cache=True, only_installed=True): """ Returns the model matching the given app_label and case-insensitive model_name. Returns None if no model is found. Raises UnavailableApp when set_available_apps() in in effect and doesn't include app_label. """ if seed_cache: self._populate() if only_installed and app_label not in self.app_labels: return None if (self.available_apps is not None and only_installed and app_label not in self.available_apps): raise UnavailableApp("App with label %s isn't available." % app_label) try: return self.app_models[app_label][model_name.lower()] except KeyError: return None def register_models(self, app_label, *models): """ Register a set of models as belonging to an app. """ for model in models: # Store as 'name: model' pair in a dictionary # in the app_models dictionary model_name = model._meta.model_name model_dict = self.app_models.setdefault(app_label, SortedDict()) if model_name in model_dict: # The same model may be imported via different paths (e.g. # appname.models and project.appname.models). We use the source # filename as a means to detect identity. fname1 = os.path.abspath(upath(sys.modules[model.__module__].__file__)) fname2 = os.path.abspath(upath(sys.modules[model_dict[model_name].__module__].__file__)) # Since the filename extension could be .py the first time and # .pyc or .pyo the second time, ignore the extension when # comparing. if os.path.splitext(fname1)[0] == os.path.splitext(fname2)[0]: continue model_dict[model_name] = model self._get_models_cache.clear() def set_available_apps(self, available): if not set(available).issubset(set(settings.INSTALLED_APPS)): extra = set(available) - set(settings.INSTALLED_APPS) raise ValueError("Available apps isn't a subset of installed " "apps, extra apps: " + ", ".join(extra)) self.available_apps = set(app.rsplit('.', 1)[-1] for app in available) def unset_available_apps(self): self.available_apps = None cache = AppCache() # These methods were always module level, so are kept that way for backwards # compatibility. get_apps = cache.get_apps get_app_paths = cache.get_app_paths get_app = cache.get_app get_app_errors = cache.get_app_errors get_models = cache.get_models get_model = cache.get_model register_models = cache.register_models load_app = cache.load_app app_cache_ready = cache.app_cache_ready