django1/django/db/migrations/state.py

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from __future__ import unicode_literals
from collections import OrderedDict
import copy
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.db.models.fields.proxy import OrderWrt
from django.conf import settings
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
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 {}
# 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)
def reload_model(self, app_label, model_name):
if 'apps' in self.__dict__: # hasattr would cache the property
# Get relations before reloading the models, as _meta.apps may change
try:
related_old = {
f.related_model for f in
self.apps.get_model(app_label, model_name)._meta.related_objects
}
except LookupError:
related_old = set()
self._reload_one_model(app_label, model_name)
# Reload models if there are relations
model = self.apps.get_model(app_label, model_name)
related_m2m = {f.related_model for f in model._meta.many_to_many}
for rel_model in related_old.union(related_m2m):
self._reload_one_model(rel_model._meta.app_label, rel_model._meta.model_name)
if related_m2m:
# Re-render this model after related models have been reloaded
self._reload_one_model(app_label, model_name)
def _reload_one_model(self, app_label, model_name):
self.apps.unregister_model(app_label, model_name)
self.models[app_label, model_name].render(self.apps)
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def clone(self):
"Returns 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()
return new_state
@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):
"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)
real_models = []
for app_label in real_apps:
app = global_apps.get_app_config(app_label)
for model in app.get_models():
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)
# 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(models.values()) + real_models
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
# If there are 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._pending_lookups.items():
try:
model = self.get_model(lookup_model[0], lookup_model[1])
except LookupError:
app_label = "%s.%s" % (lookup_model[0], lookup_model[1])
if app_label == settings.AUTH_USER_MODEL and ignore_swappable:
continue
# 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"
msg = "Lookup failed for model referenced by field {field}: {model[0]}.{model[1]}"
raise ValueError(msg.format(field=operations[0][1], model=lookup_model))
else:
do_pending_lookups(model)
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)
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
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
self.clear_cache()
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
self.name = 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.")
# Sanity-check that fields are NOT already bound to a model.
for name, field in fields:
if hasattr(field, 'model'):
raise ValueError(
'ModelState.fields cannot be bound to a model - "%s" is.' % name
)
@cached_property
def name_lower(self):
return self.name.lower()
@classmethod
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, "rel", None) and exclude_rels:
continue
if isinstance(field, OrderWrt):
continue
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,
))
if not exclude_rels:
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
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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))
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else:
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]
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.
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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,)
# Constructs all managers on the model
managers = {}
def reconstruct_manager(mgr):
as_manager, manager_path, qs_path, args, kwargs = mgr.deconstruct()
if as_manager:
qs_class = import_string(qs_path)
instance = qs_class.as_manager()
else:
manager_class = import_string(manager_path)
instance = manager_class(*args, **kwargs)
# We rely on the ordering of the creation_counter of the original
# instance
managers[mgr.name] = (mgr.creation_counter, instance)
default_manager_name = model._default_manager.name
# Make sure the default manager is always the first
if model._default_manager.use_in_migrations:
reconstruct_manager(model._default_manager)
else:
# Force this manager to be the first and thus default
managers[default_manager_name] = (0, models.Manager())
# Sort all managers by their creation counter
for _, manager, _ in sorted(model._meta.managers):
if manager.name == '_base_manager' or not manager.use_in_migrations:
continue
reconstruct_manager(manager)
# Sort all managers by their creation counter but take only name and
# instance for further processing
managers = [
(name, instance) for name, (cc, instance) in
sorted(managers.items(), key=lambda v: v[1])
]
if managers == [(default_manager_name, models.Manager())]:
managers = []
# Construct the new ModelState
return cls(
model._meta.app_label,
model._meta.object_name,
fields,
options,
bases,
managers,
)
@classmethod
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_fields(self):
"Deep-clone the fields using deconstruction"
for name, field in self.fields:
_, path, args, kwargs = field.deconstruct()
field_class = import_string(path)
yield name, field_class(*args, **kwargs)
def clone(self):
"Returns an exact copy of this ModelState"
return self.__class__(
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app_label=self.app_label,
name=self.name,
fields=list(self.construct_fields()),
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options=dict(self.options),
bases=self.bases,
managers=self.managers,
)
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)
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.construct_fields())
body['Meta'] = meta
body['__module__'] = "__fake__"
# Restore managers
for mgr_name, manager in self.managers:
body[mgr_name] = manager
# Then, make a Model object (apps.register_model is called in __new__)
return type(
str(self.name),
bases,
body,
)
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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 __repr__(self):
return "<ModelState: '%s.%s'>" % (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)
)
def __ne__(self, other):
return not (self == other)