import copy from contextlib import contextmanager from django.apps import AppConfig from django.apps.registry import Apps, apps as global_apps from django.conf import settings from django.db import models from django.db.models.fields.proxy import OrderWrt from django.db.models.fields.related import RECURSIVE_RELATIONSHIP_CONSTANT from django.db.models.options import DEFAULT_NAMES, normalize_together from django.db.models.utils import make_model_tuple from django.utils.functional import cached_property from django.utils.module_loading import import_string from django.utils.version import get_docs_version from .exceptions import InvalidBasesError def _get_app_label_and_model_name(model, app_label=''): if isinstance(model, str): split = model.split('.', 1) return tuple(split) if len(split) == 2 else (app_label, split[0]) else: return model._meta.app_label, model._meta.model_name def _get_related_models(m): """Return all models that have a direct relationship to the given model.""" related_models = [ subclass for subclass in m.__subclasses__() if issubclass(subclass, models.Model) ] related_fields_models = set() for f in m._meta.get_fields(include_parents=True, include_hidden=True): if f.is_relation and f.related_model is not None and not isinstance(f.related_model, str): related_fields_models.add(f.model) related_models.append(f.related_model) # Reverse accessors of foreign keys to proxy models are attached to their # concrete proxied model. opts = m._meta if opts.proxy and m in related_fields_models: related_models.append(opts.concrete_model) return related_models def get_related_models_tuples(model): """ Return a list of typical (app_label, model_name) tuples for all related models for the given model. """ return { (rel_mod._meta.app_label, rel_mod._meta.model_name) for rel_mod in _get_related_models(model) } def get_related_models_recursive(model): """ Return all models that have a direct or indirect relationship to the given model. Relationships are either defined by explicit relational fields, like ForeignKey, ManyToManyField or OneToOneField, or by inheriting from another model (a superclass is related to its subclasses, but not vice versa). Note, however, that a model inheriting from a concrete model is also related to its superclass through the implicit *_ptr OneToOneField on the subclass. """ seen = set() queue = _get_related_models(model) for rel_mod in queue: rel_app_label, rel_model_name = rel_mod._meta.app_label, rel_mod._meta.model_name if (rel_app_label, rel_model_name) in seen: continue seen.add((rel_app_label, rel_model_name)) queue.extend(_get_related_models(rel_mod)) return seen - {(model._meta.app_label, model._meta.model_name)} class ProjectState: """ Represent the entire project's overall state. This is the item that is passed around - do it here rather than at the app level so that cross-app FKs/etc. resolve properly. """ def __init__(self, models=None, real_apps=None): self.models = models or {} # Apps to include from main registry, usually unmigrated ones self.real_apps = real_apps or [] self.is_delayed = False def add_model(self, model_state): app_label, model_name = model_state.app_label, model_state.name_lower self.models[(app_label, model_name)] = model_state if 'apps' in self.__dict__: # hasattr would cache the property self.reload_model(app_label, model_name) def remove_model(self, app_label, model_name): del self.models[app_label, model_name] if 'apps' in self.__dict__: # hasattr would cache the property self.apps.unregister_model(app_label, model_name) # Need to do this explicitly since unregister_model() doesn't clear # the cache automatically (#24513) self.apps.clear_cache() def _find_reload_model(self, app_label, model_name, delay=False): if delay: self.is_delayed = True related_models = set() try: old_model = self.apps.get_model(app_label, model_name) except LookupError: pass else: # Get all relations to and from the old model before reloading, # as _meta.apps may change if delay: related_models = get_related_models_tuples(old_model) else: related_models = get_related_models_recursive(old_model) # Get all outgoing references from the model to be rendered model_state = self.models[(app_label, model_name)] # Directly related models are the models pointed to by ForeignKeys, # OneToOneFields, and ManyToManyFields. direct_related_models = set() for name, field in model_state.fields: if field.is_relation: if field.remote_field.model == RECURSIVE_RELATIONSHIP_CONSTANT: continue rel_app_label, rel_model_name = _get_app_label_and_model_name(field.related_model, app_label) direct_related_models.add((rel_app_label, rel_model_name.lower())) # For all direct related models recursively get all related models. related_models.update(direct_related_models) for rel_app_label, rel_model_name in direct_related_models: try: rel_model = self.apps.get_model(rel_app_label, rel_model_name) except LookupError: pass else: if delay: related_models.update(get_related_models_tuples(rel_model)) else: related_models.update(get_related_models_recursive(rel_model)) # Include the model itself related_models.add((app_label, model_name)) return related_models def reload_model(self, app_label, model_name, delay=False): if 'apps' in self.__dict__: # hasattr would cache the property related_models = self._find_reload_model(app_label, model_name, delay) self._reload(related_models) def reload_models(self, models, delay=True): if 'apps' in self.__dict__: # hasattr would cache the property related_models = set() for app_label, model_name in models: related_models.update(self._find_reload_model(app_label, model_name, delay)) self._reload(related_models) def _reload(self, related_models): # Unregister all related models with self.apps.bulk_update(): for rel_app_label, rel_model_name in related_models: self.apps.unregister_model(rel_app_label, rel_model_name) states_to_be_rendered = [] # Gather all models states of those models that will be rerendered. # This includes: # 1. All related models of unmigrated apps for model_state in self.apps.real_models: if (model_state.app_label, model_state.name_lower) in related_models: states_to_be_rendered.append(model_state) # 2. All related models of migrated apps for rel_app_label, rel_model_name in related_models: try: model_state = self.models[rel_app_label, rel_model_name] except KeyError: pass else: states_to_be_rendered.append(model_state) # Render all models self.apps.render_multiple(states_to_be_rendered) def clone(self): """Return an exact copy of this ProjectState.""" new_state = ProjectState( models={k: v.clone() for k, v in self.models.items()}, real_apps=self.real_apps, ) if 'apps' in self.__dict__: new_state.apps = self.apps.clone() new_state.is_delayed = self.is_delayed return new_state def clear_delayed_apps_cache(self): if self.is_delayed and 'apps' in self.__dict__: del self.__dict__['apps'] @cached_property def apps(self): return StateApps(self.real_apps, self.models) @property def concrete_apps(self): self.apps = StateApps(self.real_apps, self.models, ignore_swappable=True) return self.apps @classmethod def from_apps(cls, apps): """Take an Apps and return a ProjectState matching it.""" app_models = {} for model in apps.get_models(include_swapped=True): model_state = ModelState.from_model(model) app_models[(model_state.app_label, model_state.name_lower)] = model_state return cls(app_models) def __eq__(self, other): return self.models == other.models and set(self.real_apps) == set(other.real_apps) class AppConfigStub(AppConfig): """Stub of an AppConfig. Only provides a label and a dict of models.""" # Not used, but required by AppConfig.__init__ path = '' def __init__(self, label): self.label = label # App-label and app-name are not the same thing, so technically passing # in the label here is wrong. In practice, migrations don't care about # the app name, but we need something unique, and the label works fine. super().__init__(label, None) def import_models(self): self.models = self.apps.all_models[self.label] class StateApps(Apps): """ Subclass of the global Apps registry class to better handle dynamic model additions and removals. """ def __init__(self, real_apps, models, ignore_swappable=False): # Any apps in self.real_apps should have all their models included # in the render. We don't use the original model instances as there # are some variables that refer to the Apps object. # FKs/M2Ms from real apps are also not included as they just # mess things up with partial states (due to lack of dependencies) self.real_models = [] for app_label in real_apps: app = global_apps.get_app_config(app_label) for model in app.get_models(): self.real_models.append(ModelState.from_model(model, exclude_rels=True)) # Populate the app registry with a stub for each application. app_labels = {model_state.app_label for model_state in models.values()} app_configs = [AppConfigStub(label) for label in sorted([*real_apps, *app_labels])] super().__init__(app_configs) # These locks get in the way of copying as implemented in clone(), # which is called whenever Django duplicates a StateApps before # updating it. self._lock = None self.ready_event = None self.render_multiple([*models.values(), *self.real_models]) # There shouldn't be any operations pending at this point. from django.core.checks.model_checks import _check_lazy_references ignore = {make_model_tuple(settings.AUTH_USER_MODEL)} if ignore_swappable else set() errors = _check_lazy_references(self, ignore=ignore) if errors: raise ValueError("\n".join(error.msg for error in errors)) @contextmanager def bulk_update(self): # Avoid clearing each model's cache for each change. Instead, clear # all caches when we're finished updating the model instances. ready = self.ready self.ready = False try: yield finally: self.ready = ready self.clear_cache() def render_multiple(self, model_states): # We keep trying to render the models in a loop, ignoring invalid # base errors, until the size of the unrendered models doesn't # decrease by at least one, meaning there's a base dependency loop/ # missing base. if not model_states: return # Prevent that all model caches are expired for each render. with self.bulk_update(): unrendered_models = model_states while unrendered_models: new_unrendered_models = [] for model in unrendered_models: try: model.render(self) except InvalidBasesError: new_unrendered_models.append(model) if len(new_unrendered_models) == len(unrendered_models): raise InvalidBasesError( "Cannot resolve bases for %r\nThis can happen if you are inheriting models from an " "app with migrations (e.g. contrib.auth)\n in an app with no migrations; see " "https://docs.djangoproject.com/en/%s/topics/migrations/#dependencies " "for more" % (new_unrendered_models, get_docs_version()) ) unrendered_models = new_unrendered_models def clone(self): """Return a clone of this registry.""" clone = StateApps([], {}) clone.all_models = copy.deepcopy(self.all_models) clone.app_configs = copy.deepcopy(self.app_configs) # Set the pointer to the correct app registry. for app_config in clone.app_configs.values(): app_config.apps = clone # No need to actually clone them, they'll never change clone.real_models = self.real_models return clone def register_model(self, app_label, model): self.all_models[app_label][model._meta.model_name] = model if app_label not in self.app_configs: self.app_configs[app_label] = AppConfigStub(app_label) self.app_configs[app_label].apps = self self.app_configs[app_label].models = {} self.app_configs[app_label].models[model._meta.model_name] = model self.do_pending_operations(model) self.clear_cache() def unregister_model(self, app_label, model_name): try: del self.all_models[app_label][model_name] del self.app_configs[app_label].models[model_name] except KeyError: pass class ModelState: """ Represent a Django Model. Don't use the actual Model class as it's not designed to have its options changed - instead, mutate this one and then render it into a Model as required. Note that while you are allowed to mutate .fields, you are not allowed to mutate the Field instances inside there themselves - you must instead assign new ones, as these are not detached during a clone. """ def __init__(self, app_label, name, fields, options=None, bases=None, managers=None): self.app_label = app_label self.name = name self.fields = fields self.options = options or {} self.options.setdefault('indexes', []) self.options.setdefault('constraints', []) self.bases = bases or (models.Model,) self.managers = managers or [] # Sanity-check that fields is NOT a dict. It must be ordered. if isinstance(self.fields, dict): raise ValueError("ModelState.fields cannot be a dict - it must be a list of 2-tuples.") for name, field in fields: # Sanity-check that fields are NOT already bound to a model. if hasattr(field, 'model'): raise ValueError( 'ModelState.fields cannot be bound to a model - "%s" is.' % name ) # Sanity-check that relation fields are NOT referring to a model class. if field.is_relation and hasattr(field.related_model, '_meta'): raise ValueError( 'ModelState.fields cannot refer to a model class - "%s.to" does. ' 'Use a string reference instead.' % name ) if field.many_to_many and hasattr(field.remote_field.through, '_meta'): raise ValueError( 'ModelState.fields cannot refer to a model class - "%s.through" does. ' 'Use a string reference instead.' % name ) # Sanity-check that indexes have their name set. for index in self.options['indexes']: if not index.name: raise ValueError( "Indexes passed to ModelState require a name attribute. " "%r doesn't have one." % index ) @cached_property def name_lower(self): return self.name.lower() @classmethod def from_model(cls, model, exclude_rels=False): """Given a model, return a ModelState representing it.""" # Deconstruct the fields fields = [] for field in model._meta.local_fields: if getattr(field, "remote_field", None) and exclude_rels: continue if isinstance(field, OrderWrt): continue name = field.name try: fields.append((name, field.clone())) except TypeError as e: raise TypeError("Couldn't reconstruct field %s on %s: %s" % ( name, model._meta.label, e, )) if not exclude_rels: for field in model._meta.local_many_to_many: name = field.name try: fields.append((name, field.clone())) except TypeError as e: raise TypeError("Couldn't reconstruct m2m field %s on %s: %s" % ( name, model._meta.object_name, e, )) # Extract the options options = {} for name in DEFAULT_NAMES: # Ignore some special options if name in ["apps", "app_label"]: continue elif name in model._meta.original_attrs: if name == "unique_together": ut = model._meta.original_attrs["unique_together"] options[name] = set(normalize_together(ut)) elif name == "index_together": it = model._meta.original_attrs["index_together"] options[name] = set(normalize_together(it)) elif name == "indexes": indexes = [idx.clone() for idx in model._meta.indexes] for index in indexes: if not index.name: index.set_name_with_model(model) options['indexes'] = indexes elif name == 'constraints': options['constraints'] = [con.clone() for con in model._meta.constraints] else: options[name] = model._meta.original_attrs[name] # If we're ignoring relationships, remove all field-listing model # options (that option basically just means "make a stub model") if exclude_rels: for key in ["unique_together", "index_together", "order_with_respect_to"]: if key in options: del options[key] # Private fields are ignored, so remove options that refer to them. elif options.get('order_with_respect_to') in {field.name for field in model._meta.private_fields}: del options['order_with_respect_to'] def flatten_bases(model): bases = [] for base in model.__bases__: if hasattr(base, "_meta") and base._meta.abstract: bases.extend(flatten_bases(base)) else: bases.append(base) return bases # We can't rely on __mro__ directly because we only want to flatten # abstract models and not the whole tree. However by recursing on # __bases__ we may end up with duplicates and ordering issues, we # therefore discard any duplicates and reorder the bases according # to their index in the MRO. flattened_bases = sorted(set(flatten_bases(model)), key=lambda x: model.__mro__.index(x)) # Make our record bases = tuple( ( base._meta.label_lower if hasattr(base, "_meta") else base ) for base in flattened_bases ) # Ensure at least one base inherits from models.Model if not any((isinstance(base, str) or issubclass(base, models.Model)) for base in bases): bases = (models.Model,) managers = [] manager_names = set() default_manager_shim = None for manager in model._meta.managers: if manager.name in manager_names: # Skip overridden managers. continue elif manager.use_in_migrations: # Copy managers usable in migrations. new_manager = copy.copy(manager) new_manager._set_creation_counter() elif manager is model._base_manager or manager is model._default_manager: # Shim custom managers used as default and base managers. new_manager = models.Manager() new_manager.model = manager.model new_manager.name = manager.name if manager is model._default_manager: default_manager_shim = new_manager else: continue manager_names.add(manager.name) managers.append((manager.name, new_manager)) # Ignore a shimmed default manager called objects if it's the only one. if managers == [('objects', default_manager_shim)]: managers = [] # Construct the new ModelState return cls( model._meta.app_label, model._meta.object_name, fields, options, bases, managers, ) def construct_managers(self): """Deep-clone the managers using deconstruction.""" # Sort all managers by their creation counter sorted_managers = sorted(self.managers, key=lambda v: v[1].creation_counter) for mgr_name, manager in sorted_managers: as_manager, manager_path, qs_path, args, kwargs = manager.deconstruct() if as_manager: qs_class = import_string(qs_path) yield mgr_name, qs_class.as_manager() else: manager_class = import_string(manager_path) yield mgr_name, manager_class(*args, **kwargs) def clone(self): """Return an exact copy of this ModelState.""" return self.__class__( app_label=self.app_label, name=self.name, fields=list(self.fields), # Since options are shallow-copied here, operations such as # AddIndex must replace their option (e.g 'indexes') rather # than mutating it. options=dict(self.options), bases=self.bases, managers=list(self.managers), ) def render(self, apps): """Create a Model object from our current state into the given apps.""" # First, make a Meta object meta_contents = {'app_label': self.app_label, 'apps': apps, **self.options} meta = type("Meta", (), meta_contents) # Then, work out our bases try: bases = tuple( (apps.get_model(base) if isinstance(base, str) else base) for base in self.bases ) except LookupError: raise InvalidBasesError("Cannot resolve one or more bases from %r" % (self.bases,)) # Turn fields into a dict for the body, add other bits body = {name: field.clone() for name, field in self.fields} body['Meta'] = meta body['__module__'] = "__fake__" # Restore managers body.update(self.construct_managers()) # Then, make a Model object (apps.register_model is called in __new__) return type(self.name, bases, body) def get_field_by_name(self, name): for fname, field in self.fields: if fname == name: return field raise ValueError("No field called %s on model %s" % (name, self.name)) def get_index_by_name(self, name): for index in self.options['indexes']: if index.name == name: return index raise ValueError("No index named %s on model %s" % (name, self.name)) def get_constraint_by_name(self, name): for constraint in self.options['constraints']: if constraint.name == name: return constraint raise ValueError('No constraint named %s on model %s' % (name, self.name)) def __repr__(self): return "<%s: '%s.%s'>" % (self.__class__.__name__, self.app_label, self.name) def __eq__(self, other): return ( (self.app_label == other.app_label) and (self.name == other.name) and (len(self.fields) == len(other.fields)) and all((k1 == k2 and (f1.deconstruct()[1:] == f2.deconstruct()[1:])) for (k1, f1), (k2, f2) in zip(self.fields, other.fields)) and (self.options == other.options) and (self.bases == other.bases) and (self.managers == other.managers) )