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from django.apps import AppConfig
from django.apps.registry import Apps
from django.db import models
from django.db.models.options import DEFAULT_NAMES, normalize_unique_together
from django.utils import six
from django.utils.module_loading import import_by_path
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):
self.models = models or {}
self.apps = None
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())
)
def render(self):
"Turns the project state into actual models in a new Apps"
if self.apps is None:
# 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(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())
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
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
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.
"""
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_by_path(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_by_path(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_unique_together(ut))
else:
options[name] = model._meta.original_attrs[name]
# Make our record
bases = tuple(
(
"%s.%s" % (base._meta.app_label, base._meta.model_name)
if hasattr(base, "_meta") else
base
)
for base in model.__bases__
if (not hasattr(base, "_meta") or not base._meta.abstract)
)
# 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_by_path(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("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(
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)
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