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ba7206cd81
Returning None on errors required unpythonic error checking and was inconsistent with get_app_config. get_model was a private API until the previous commit, but given that it was certainly used in third party software, the change is explained in the release notes. Applied the same change to get_registered_model, which is a new private API introduced during the recent refactoring.
231 lines
8.6 KiB
Python
231 lines
8.6 KiB
Python
from django.apps import AppConfig
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from django.apps.registry import Apps
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from django.db import models
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from django.db.models.options import DEFAULT_NAMES, normalize_unique_together
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from django.utils import six
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from django.utils.module_loading import import_by_path
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class InvalidBasesError(ValueError):
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pass
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class ProjectState(object):
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"""
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Represents the entire project's overall state.
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This is the item that is passed around - we do it here rather than at the
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app level so that cross-app FKs/etc. resolve properly.
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"""
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def __init__(self, models=None):
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self.models = models or {}
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self.apps = None
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def add_model_state(self, model_state):
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self.models[(model_state.app_label, model_state.name.lower())] = model_state
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def clone(self):
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"Returns an exact copy of this ProjectState"
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return ProjectState(
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models=dict((k, v.clone()) for k, v in self.models.items())
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)
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def render(self):
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"Turns the project state into actual models in a new Apps"
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if self.apps is None:
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self.apps = Apps()
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# Populate the app registry with a stub for each application.
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app_labels = set(model_state.app_label for model_state in self.models.values())
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app_configs = [AppConfigStub(label) for label in sorted(app_labels)]
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self.apps.populate_apps(app_configs)
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self.apps.populate_models()
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# We keep trying to render the models in a loop, ignoring invalid
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# base errors, until the size of the unrendered models doesn't
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# decrease by at least one, meaning there's a base dependency loop/
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# missing base.
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unrendered_models = list(self.models.values())
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while unrendered_models:
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new_unrendered_models = []
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for model in unrendered_models:
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try:
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model.render(self.apps)
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except InvalidBasesError:
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new_unrendered_models.append(model)
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if len(new_unrendered_models) == len(unrendered_models):
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raise InvalidBasesError("Cannot resolve bases for %r" % new_unrendered_models)
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unrendered_models = new_unrendered_models
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return self.apps
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@classmethod
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def from_apps(cls, apps):
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"Takes in an Apps and returns a ProjectState matching it"
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app_models = {}
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for model in apps.get_models():
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model_state = ModelState.from_model(model)
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app_models[(model_state.app_label, model_state.name.lower())] = model_state
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return cls(app_models)
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def __eq__(self, other):
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if set(self.models.keys()) != set(other.models.keys()):
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return False
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return all(model == other.models[key] for key, model in self.models.items())
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def __ne__(self, other):
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return not (self == other)
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class AppConfigStub(AppConfig):
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"""
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Stubs a Django AppConfig. Only provides a label and a dict of models.
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"""
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def __init__(self, label):
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self.label = label
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self.path = None
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super(AppConfigStub, self).__init__(None, None)
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def import_models(self, all_models):
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self.models = all_models
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class ModelState(object):
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"""
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Represents a Django Model. We don't use the actual Model class
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as it's not designed to have its options changed - instead, we
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mutate this one and then render it into a Model as required.
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Note that while you are allowed to mutate .fields, you are not allowed
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to mutate the Field instances inside there themselves - you must instead
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assign new ones, as these are not detached during a clone.
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"""
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def __init__(self, app_label, name, fields, options=None, bases=None):
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self.app_label = app_label
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self.name = name
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self.fields = fields
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self.options = options or {}
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self.bases = bases or (models.Model, )
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# Sanity-check that fields is NOT a dict. It must be ordered.
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if isinstance(self.fields, dict):
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raise ValueError("ModelState.fields cannot be a dict - it must be a list of 2-tuples.")
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@classmethod
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def from_model(cls, model):
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"""
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Feed me a model, get a ModelState representing it out.
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"""
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# Deconstruct the fields
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fields = []
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for field in model._meta.local_fields:
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name, path, args, kwargs = field.deconstruct()
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field_class = import_by_path(path)
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try:
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fields.append((name, field_class(*args, **kwargs)))
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except TypeError as e:
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raise TypeError("Couldn't reconstruct field %s on %s.%s: %s" % (
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name,
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model._meta.app_label,
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model._meta.object_name,
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e,
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))
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for field in model._meta.local_many_to_many:
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name, path, args, kwargs = field.deconstruct()
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field_class = import_by_path(path)
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try:
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fields.append((name, field_class(*args, **kwargs)))
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except TypeError as e:
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raise TypeError("Couldn't reconstruct m2m field %s on %s: %s" % (
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name,
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model._meta.object_name,
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e,
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))
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# Extract the options
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options = {}
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for name in DEFAULT_NAMES:
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# Ignore some special options
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if name in ["apps", "app_label"]:
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continue
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elif name in model._meta.original_attrs:
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if name == "unique_together":
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ut = model._meta.original_attrs["unique_together"]
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options[name] = set(normalize_unique_together(ut))
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else:
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options[name] = model._meta.original_attrs[name]
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# Make our record
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bases = tuple(
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("%s.%s" % (base._meta.app_label, base._meta.object_name.lower()) if hasattr(base, "_meta") else base)
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for base in model.__bases__
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if (not hasattr(base, "_meta") or not base._meta.abstract)
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)
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if not bases:
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bases = (models.Model, )
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return cls(
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model._meta.app_label,
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model._meta.object_name,
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fields,
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options,
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bases,
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)
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def clone(self):
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"Returns an exact copy of this ModelState"
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# We deep-clone the fields using deconstruction
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fields = []
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for name, field in self.fields:
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_, path, args, kwargs = field.deconstruct()
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field_class = import_by_path(path)
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fields.append((name, field_class(*args, **kwargs)))
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# Now make a copy
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return self.__class__(
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app_label=self.app_label,
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name=self.name,
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fields=fields,
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options=dict(self.options),
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bases=self.bases,
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)
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def render(self, apps):
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"Creates a Model object from our current state into the given apps"
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# First, make a Meta object
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meta_contents = {'app_label': self.app_label, "apps": apps}
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meta_contents.update(self.options)
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if "unique_together" in meta_contents:
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meta_contents["unique_together"] = list(meta_contents["unique_together"])
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meta = type("Meta", tuple(), meta_contents)
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# Then, work out our bases
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try:
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bases = tuple(
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(apps.get_model(*base.split(".", 1)) if isinstance(base, six.string_types) else base)
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for base in self.bases
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)
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except LookupError:
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raise InvalidBasesError("Cannot resolve one or more bases from %r" % (self.bases,))
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# Turn fields into a dict for the body, add other bits
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body = dict(self.fields)
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body['Meta'] = meta
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body['__module__'] = "__fake__"
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# Then, make a Model object
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return type(
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self.name,
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bases,
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body,
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)
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def get_field_by_name(self, name):
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for fname, field in self.fields:
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if fname == name:
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return field
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raise ValueError("No field called %s on model %s" % (name, self.name))
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def __eq__(self, other):
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return (
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(self.app_label == other.app_label) and
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(self.name == other.name) and
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(len(self.fields) == len(other.fields)) and
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all((k1 == k2 and (f1.deconstruct()[1:] == f2.deconstruct()[1:])) for (k1, f1), (k2, f2) in zip(self.fields, other.fields)) and
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(self.options == other.options) and
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(self.bases == other.bases)
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)
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def __ne__(self, other):
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return not (self == other)
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