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from __future__ import unicode_literals
import copy
from collections import OrderedDict
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 import six
from django.utils.encoding import force_text, smart_text
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, six.string_types):
split = model.split('.', 1)
return (tuple(split) if len(split) == 2 else (app_label, split[0]))
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, six.string_types):
# 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:
return related_models
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:
seen.add((rel_app_label, rel_model_name))
return seen - {(model._meta.app_label, model._meta.model_name)}
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 {}
# Apps to include from main registry, usually unmigrated ones
self.real_apps = real_apps or []
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)
def reload_model(self, app_label, model_name):
if 'apps' in self.__dict__: # hasattr would cache the property
old_model = self.apps.get_model(app_label, model_name)
except LookupError:
related_models = set()
# Get all relations to and from the old model before reloading,
# as _meta.apps may change
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:
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.
for rel_app_label, rel_model_name in direct_related_models:
rel_model = self.apps.get_model(rel_app_label, rel_model_name)
except LookupError:
# Include the model itself
related_models.add((app_label, model_name))
# 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:
# 2. All related models of migrated apps
for rel_app_label, rel_model_name in related_models:
model_state = self.models[rel_app_label, rel_model_name]
except KeyError:
# Render all models
def clone(self):
"Returns an exact copy of this ProjectState"
new_state = ProjectState(
models={k: v.clone() for k, v in self.models.items()},
if 'apps' in self.__dict__:
new_state.apps = self.apps.clone()
return new_state
def apps(self):
return StateApps(self.real_apps, self.models)
def concrete_apps(self):
self.apps = StateApps(self.real_apps, self.models, ignore_swappable=True)
return self.apps
def from_apps(cls, apps):
"Takes in an Apps and returns 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):
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):
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(AppConfigStub, self).__init__(label, None)
def import_models(self, all_models):
self.models = all_models
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 + list(app_labels))]
super(StateApps, self).__init__(app_configs)
self.render_multiple(list(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))
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
self.ready = ready
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:
# 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:
except InvalidBasesError:
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 "
" "
"for more" % (new_unrendered_models, get_docs_version())
unrendered_models = new_unrendered_models
def clone(self):
Return a clone of this registry, mainly used by the migration framework.
clone = StateApps([], {})
clone.all_models = copy.deepcopy(self.all_models)
clone.app_configs = copy.deepcopy(self.app_configs)
# 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].models = OrderedDict()
self.app_configs[app_label].models[model._meta.model_name] = model
def unregister_model(self, app_label, model_name):
del self.all_models[app_label][model_name]
del self.app_configs[app_label].models[model_name]
except KeyError:
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, managers=None):
self.app_label = app_label = force_text(name)
self.fields = fields
self.options = options or {}
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 - "" 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
def name_lower(self):
def from_model(cls, model, exclude_rels=False):
Feed me a model, get a ModelState representing it out.
# Deconstruct the fields
fields = []
for field in model._meta.local_fields:
if getattr(field, "remote_field", None) and exclude_rels:
if isinstance(field, OrderWrt):
name = force_text(, strings_only=True)
fields.append((name, field.clone()))
except TypeError as e:
raise TypeError("Couldn't reconstruct field %s on %s: %s" % (
if not exclude_rels:
for field in model._meta.local_many_to_many:
name = force_text(, strings_only=True)
fields.append((name, field.clone()))
except TypeError as e:
raise TypeError("Couldn't reconstruct m2m field %s on %s: %s" % (
# Extract the options
options = {}
for name in DEFAULT_NAMES:
# Ignore some special options
if name in ["apps", "app_label"]:
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))
options[name] = model._meta.original_attrs[name]
# Force-convert all options to text_type (#23226)
options = cls.force_text_recursive(options)
# 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 { 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:
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(
if hasattr(base, "_meta") else
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,)
managers = []
# Make sure the default manager is always first since ordering chooses
# the default manager.
if not model._default_manager.auto_created:
if model._default_manager.use_in_migrations:
default_manager = copy.copy(model._default_manager)
# If the default manager doesn't have `use_in_migrations = True`,
# shim a default manager so another manager isn't promoted in its
# place.
default_manager = models.Manager()
default_manager.model = model =
managers.append((force_text(, default_manager))
for manager in model._meta.managers:
if manager.use_in_migrations and manager is not model._default_manager:
manager = copy.copy(manager)
managers.append((force_text(, manager))
# Construct the new ModelState
return cls(
def force_text_recursive(cls, value):
if isinstance(value, six.string_types):
return smart_text(value)
elif isinstance(value, list):
return [cls.force_text_recursive(x) for x in value]
elif isinstance(value, tuple):
return tuple(cls.force_text_recursive(x) for x in value)
elif isinstance(value, set):
return set(cls.force_text_recursive(x) for x in value)
elif isinstance(value, dict):
return {
cls.force_text_recursive(k): cls.force_text_recursive(v)
for k, v in value.items()
return value
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:
mgr_name = force_text(mgr_name)
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()
manager_class = import_string(manager_path)
yield mgr_name, manager_class(*args, **kwargs)
def clone(self):
"Returns an exact copy of this ModelState"
return self.__class__(
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 = type(str("Meta"), tuple(), meta_contents)
# Then, work out our bases
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 = {name: field.clone() for name, field in self.fields}
body['Meta'] = meta
body['__module__'] = "__fake__"
# Restore managers
# Then, make a Model object (apps.register_model is called in __new__)
return type(
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,
def __repr__(self):
return "<ModelState: '%s.%s'>" % (self.app_label,
def __eq__(self, other):
return (
(self.app_label == other.app_label) and
( == 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)
def __ne__(self, other):
return not (self == other)
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