from __future__ import unicode_literals from django.apps import AppConfig from django.apps.registry import Apps, apps as global_apps from django.db import models from django.db.models.options import DEFAULT_NAMES, normalize_together from django.db.models.fields.related import do_pending_lookups from django.utils import six from django.utils.module_loading import import_string class InvalidBasesError(ValueError): pass class ProjectState(object): """ Represents the entire project's overall state. This is the item that is passed around - we 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 {} self.apps = None # Apps to include from main registry, usually unmigrated ones self.real_apps = real_apps or [] def add_model_state(self, model_state): self.models[(model_state.app_label, model_state.name.lower())] = model_state def clone(self): "Returns an exact copy of this ProjectState" return ProjectState( models=dict((k, v.clone()) for k, v in self.models.items()), real_apps=self.real_apps, ) def render(self, include_real=None): "Turns the project state into actual models in a new Apps" if self.apps is None: # 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. real_models = [] for app_label in self.real_apps: app = global_apps.get_app_config(app_label) for model in app.get_models(): real_models.append(ModelState.from_model(model)) # Populate the app registry with a stub for each application. app_labels = set(model_state.app_label for model_state in self.models.values()) self.apps = Apps([AppConfigStub(label) for label in sorted(self.real_apps + list(app_labels))]) # 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. unrendered_models = list(self.models.values()) + real_models while unrendered_models: new_unrendered_models = [] for model in unrendered_models: try: model.render(self.apps) except InvalidBasesError: new_unrendered_models.append(model) if len(new_unrendered_models) == len(unrendered_models): raise InvalidBasesError("Cannot resolve bases for %r" % new_unrendered_models) unrendered_models = new_unrendered_models # make sure apps has no dangling references if self.apps._pending_lookups: # There's some lookups left. See if we can first resolve them # ourselves - sometimes fields are added after class_prepared is sent for lookup_model, operations in self.apps._pending_lookups.items(): try: model = self.apps.get_model(lookup_model[0], lookup_model[1]) except LookupError: # Raise an error with a best-effort helpful message # (only for the first issue). Error message should look like: # "ValueError: Lookup failed for model referenced by # field migrations.Book.author: migrations.Author" raise ValueError("Lookup failed for model referenced by field {field}: {model[0]}.{model[1]}".format( field=operations[0][1], model=lookup_model )) else: do_pending_lookups(model) return self.apps @classmethod def from_apps(cls, apps): "Takes in an Apps and returns a ProjectState matching it" app_models = {} for model in apps.get_models(): 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): if set(self.models.keys()) != set(other.models.keys()): return False if set(self.real_apps) != set(other.real_apps): return False return all(model == other.models[key] for key, model in self.models.items()) def __ne__(self, other): return not (self == other) class AppConfigStub(AppConfig): """ Stubs a Django AppConfig. Only provides a label, and a dict of models. """ # Not used, but required by AppConfig.__init__ path = '' def __init__(self, label): super(AppConfigStub, self).__init__(label, None) def import_models(self, all_models): self.models = all_models class ModelState(object): """ Represents a Django Model. We don't use the actual Model class as it's not designed to have its options changed - instead, we 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): self.app_label = app_label self.name = name self.fields = fields self.options = options or {} self.bases = bases or (models.Model, ) # 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.") @classmethod def from_model(cls, model): """ Feed me a model, get a ModelState representing it out. """ # Deconstruct the fields fields = [] for field in model._meta.local_fields: name, path, args, kwargs = field.deconstruct() field_class = import_string(path) try: fields.append((name, field_class(*args, **kwargs))) except TypeError as e: raise TypeError("Couldn't reconstruct field %s on %s.%s: %s" % ( name, model._meta.app_label, model._meta.object_name, e, )) for field in model._meta.local_many_to_many: name, path, args, kwargs = field.deconstruct() field_class = import_string(path) try: fields.append((name, field_class(*args, **kwargs))) 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)) else: options[name] = model._meta.original_attrs[name] 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( ( "%s.%s" % (base._meta.app_label, base._meta.model_name) 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, six.string_types) or issubclass(base, models.Model)) for base in bases): bases = (models.Model,) return cls( model._meta.app_label, model._meta.object_name, fields, options, bases, ) def clone(self): "Returns an exact copy of this ModelState" # We deep-clone the fields using deconstruction fields = [] for name, field in self.fields: _, path, args, kwargs = field.deconstruct() field_class = import_string(path) fields.append((name, field_class(*args, **kwargs))) # Now make a copy return self.__class__( app_label=self.app_label, name=self.name, fields=fields, options=dict(self.options), bases=self.bases, ) def render(self, apps): "Creates 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} meta_contents.update(self.options) if "unique_together" in meta_contents: meta_contents["unique_together"] = list(meta_contents["unique_together"]) meta = type(str("Meta"), tuple(), meta_contents) # Then, work out our bases try: bases = tuple( (apps.get_model(base) if isinstance(base, six.string_types) 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 = dict(self.fields) body['Meta'] = meta body['__module__'] = "__fake__" # Then, make a Model object return type( str(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 __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) ) def __ne__(self, other): return not (self == other)