392 lines
16 KiB
Python
392 lines
16 KiB
Python
from __future__ import unicode_literals
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from django.apps import AppConfig
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from django.apps.registry import Apps, apps as global_apps
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from django.db import models
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from django.db.models.options import DEFAULT_NAMES, normalize_together
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from django.db.models.fields.related import do_pending_lookups
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from django.db.models.fields.proxy import OrderWrt
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from django.conf import settings
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from django.utils import six
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from django.utils.encoding import force_text, smart_text
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from django.utils.module_loading import import_string
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from django.utils.version import get_docs_version
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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, real_apps=None):
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self.models = models or {}
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self.apps = None
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# Apps to include from main registry, usually unmigrated ones
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self.real_apps = real_apps or []
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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={k: v.clone() for k, v in self.models.items()},
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real_apps=self.real_apps,
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)
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def render(self, include_real=None, ignore_swappable=False, skip_cache=False):
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"Turns the project state into actual models in a new Apps"
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if self.apps is None or skip_cache:
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# Any apps in self.real_apps should have all their models included
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# in the render. We don't use the original model instances as there
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# are some variables that refer to the Apps object.
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# FKs/M2Ms from real apps are also not included as they just
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# mess things up with partial states (due to lack of dependencies)
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real_models = []
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for app_label in self.real_apps:
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app = global_apps.get_app_config(app_label)
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for model in app.get_models():
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real_models.append(ModelState.from_model(model, exclude_rels=True))
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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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self.apps = Apps([AppConfigStub(label) for label in sorted(self.real_apps + list(app_labels))])
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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()) + real_models
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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(
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"Cannot resolve bases for %r\nThis can happen if you are inheriting models from an "
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"app with migrations (e.g. contrib.auth)\n in an app with no migrations; see "
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"https://docs.djangoproject.com/en/%s/topics/migrations/#dependencies "
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"for more" % (new_unrendered_models, get_docs_version())
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)
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unrendered_models = new_unrendered_models
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# make sure apps has no dangling references
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if self.apps._pending_lookups:
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# There's some lookups left. See if we can first resolve them
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# ourselves - sometimes fields are added after class_prepared is sent
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for lookup_model, operations in self.apps._pending_lookups.items():
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try:
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model = self.apps.get_model(lookup_model[0], lookup_model[1])
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except LookupError:
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app_label = "%s.%s" % (lookup_model[0], lookup_model[1])
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if app_label == settings.AUTH_USER_MODEL and ignore_swappable:
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continue
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# Raise an error with a best-effort helpful message
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# (only for the first issue). Error message should look like:
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# "ValueError: Lookup failed for model referenced by
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# field migrations.Book.author: migrations.Author"
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msg = "Lookup failed for model referenced by field {field}: {model[0]}.{model[1]}"
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raise ValueError(msg.format(field=operations[0][1], model=lookup_model))
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else:
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do_pending_lookups(model)
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try:
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return self.apps
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finally:
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if skip_cache:
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self.apps = None
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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(include_swapped=True):
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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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if set(self.real_apps) != set(other.real_apps):
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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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# Not used, but required by AppConfig.__init__
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path = ''
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def __init__(self, label):
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self.label = label
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# App-label and app-name are not the same thing, so technically passing
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# in the label here is wrong. In practice, migrations don't care about
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# the app name, but we need something unique, and the label works fine.
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super(AppConfigStub, self).__init__(label, 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, managers=None):
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self.app_label = app_label
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self.name = force_text(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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self.managers = managers or []
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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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# Sanity-check that fields are NOT already bound to a model.
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for name, field in fields:
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if hasattr(field, 'model'):
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raise ValueError(
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'ModelState.fields cannot be bound to a model - "%s" is.' % name
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)
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@classmethod
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def from_model(cls, model, exclude_rels=False):
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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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if getattr(field, "rel", None) and exclude_rels:
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continue
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if isinstance(field, OrderWrt):
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continue
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name, path, args, kwargs = field.deconstruct()
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field_class = import_string(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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if not exclude_rels:
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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_string(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_together(ut))
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elif name == "index_together":
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it = model._meta.original_attrs["index_together"]
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options[name] = set(normalize_together(it))
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else:
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options[name] = model._meta.original_attrs[name]
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# Force-convert all options to text_type (#23226)
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options = cls.force_text_recursive(options)
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# If we're ignoring relationships, remove all field-listing model
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# options (that option basically just means "make a stub model")
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if exclude_rels:
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for key in ["unique_together", "index_together", "order_with_respect_to"]:
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if key in options:
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del options[key]
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def flatten_bases(model):
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bases = []
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for base in model.__bases__:
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if hasattr(base, "_meta") and base._meta.abstract:
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bases.extend(flatten_bases(base))
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else:
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bases.append(base)
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return bases
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# We can't rely on __mro__ directly because we only want to flatten
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# abstract models and not the whole tree. However by recursing on
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# __bases__ we may end up with duplicates and ordering issues, we
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# therefore discard any duplicates and reorder the bases according
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# to their index in the MRO.
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flattened_bases = sorted(set(flatten_bases(model)), key=lambda x: model.__mro__.index(x))
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# Make our record
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bases = tuple(
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(
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"%s.%s" % (base._meta.app_label, base._meta.model_name)
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if hasattr(base, "_meta") else
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base
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)
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for base in flattened_bases
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)
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# Ensure at least one base inherits from models.Model
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if not any((isinstance(base, six.string_types) or issubclass(base, models.Model)) for base in bases):
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bases = (models.Model,)
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# Constructs all managers on the model
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managers = {}
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def reconstruct_manager(mgr):
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as_manager, manager_path, qs_path, args, kwargs = mgr.deconstruct()
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if as_manager:
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qs_class = import_string(qs_path)
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instance = qs_class.as_manager()
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else:
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manager_class = import_string(manager_path)
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instance = manager_class(*args, **kwargs)
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# We rely on the ordering of the creation_counter of the original
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# instance
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managers[mgr.name] = (mgr.creation_counter, instance)
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default_manager_name = model._default_manager.name
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# Make sure the default manager is always the first
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if model._default_manager.use_in_migrations:
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reconstruct_manager(model._default_manager)
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else:
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# Force this manager to be the first and thus default
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managers[default_manager_name] = (0, models.Manager())
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# Sort all managers by their creation counter
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for _, manager, _ in sorted(model._meta.managers):
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if manager.name == '_base_manager' or not manager.use_in_migrations:
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continue
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reconstruct_manager(manager)
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# Sort all managers by their creation counter but take only name and
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# instance for further processing
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managers = [
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(name, instance) for name, (cc, instance) in
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sorted(managers.items(), key=lambda v: v[1])
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]
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if managers == [(default_manager_name, models.Manager())]:
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managers = []
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# Construct the new ModelState
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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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managers,
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)
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@classmethod
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def force_text_recursive(cls, value):
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if isinstance(value, six.string_types):
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return smart_text(value)
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elif isinstance(value, list):
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return [cls.force_text_recursive(x) for x in value]
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elif isinstance(value, tuple):
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return tuple(cls.force_text_recursive(x) for x in value)
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elif isinstance(value, set):
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return set(cls.force_text_recursive(x) for x in value)
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elif isinstance(value, dict):
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return {
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cls.force_text_recursive(k): cls.force_text_recursive(v)
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for k, v in value.items()
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}
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return value
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def construct_fields(self):
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"Deep-clone the fields using deconstruction"
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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_string(path)
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yield name, field_class(*args, **kwargs)
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def clone(self):
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"Returns an exact copy of this ModelState"
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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=list(self.construct_fields()),
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options=dict(self.options),
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bases=self.bases,
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managers=self.managers,
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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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meta = type(str("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) 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.construct_fields())
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body['Meta'] = meta
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body['__module__'] = "__fake__"
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# Restore managers
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for mgr_name, manager in self.managers:
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body[mgr_name] = manager
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# Then, make a Model object
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return type(
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str(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 __repr__(self):
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return "<ModelState: '%s.%s'>" % (self.app_label, 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:]))
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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) and
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(self.managers == other.managers)
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)
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def __ne__(self, other):
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return not (self == other)
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