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Enso-Bot/venv/Lib/site-packages/south/orm.py

408 lines
15 KiB
Python

"""
South's fake ORM; lets you not have to write SQL inside migrations.
Roughly emulates the real Django ORM, to a point.
"""
from __future__ import print_function
import inspect
from django.db import models
from django.db.models.loading import cache
from django.core.exceptions import ImproperlyConfigured
from south.db import db
from south.utils import ask_for_it_by_name, datetime_utils
from south.hacks import hacks
from south.exceptions import UnfreezeMeLater, ORMBaseNotIncluded, ImpossibleORMUnfreeze
from south.utils.py3 import string_types
class ModelsLocals(object):
"""
Custom dictionary-like class to be locals();
falls back to lowercase search for items that don't exist
(because we store model names as lowercase).
"""
def __init__(self, data):
self.data = data
def __getitem__(self, key):
try:
return self.data[key]
except KeyError:
return self.data[key.lower()]
# Stores already-created ORMs.
_orm_cache = {}
def FakeORM(*args):
"""
Creates a Fake Django ORM.
This is actually a memoised constructor; the real class is _FakeORM.
"""
if not args in _orm_cache:
_orm_cache[args] = _FakeORM(*args)
return _orm_cache[args]
class LazyFakeORM(object):
"""
In addition to memoising the ORM call, this function lazily generates them
for a Migration class. Assign the result of this to (for example)
.orm, and as soon as .orm is accessed the ORM will be created.
"""
def __init__(self, *args):
self._args = args
self.orm = None
def __get__(self, obj, type=None):
if not self.orm:
self.orm = FakeORM(*self._args)
return self.orm
class _FakeORM(object):
"""
Simulates the Django ORM at some point in time,
using a frozen definition on the Migration class.
"""
def __init__(self, cls, app):
self.default_app = app
self.cls = cls
# Try loading the models off the migration class; default to no models.
self.models = {}
try:
self.models_source = cls.models
except AttributeError:
return
# Start a 'new' AppCache
hacks.clear_app_cache()
# Now, make each model's data into a FakeModel
# We first make entries for each model that are just its name
# This allows us to have circular model dependency loops
model_names = []
for name, data in self.models_source.items():
# Make sure there's some kind of Meta
if "Meta" not in data:
data['Meta'] = {}
try:
app_label, model_name = name.split(".", 1)
except ValueError:
app_label = self.default_app
model_name = name
# If there's an object_name in the Meta, use it and remove it
if "object_name" in data['Meta']:
model_name = data['Meta']['object_name']
del data['Meta']['object_name']
name = "%s.%s" % (app_label, model_name)
self.models[name.lower()] = name
model_names.append((name.lower(), app_label, model_name, data))
# Loop until model_names is entry, or hasn't shrunk in size since
# last iteration.
# The make_model method can ask to postpone a model; it's then pushed
# to the back of the queue. Because this is currently only used for
# inheritance, it should thus theoretically always decrease by one.
last_size = None
while model_names:
# First, make sure we've shrunk.
if len(model_names) == last_size:
raise ImpossibleORMUnfreeze()
last_size = len(model_names)
# Make one run through
postponed_model_names = []
for name, app_label, model_name, data in model_names:
try:
self.models[name] = self.make_model(app_label, model_name, data)
except UnfreezeMeLater:
postponed_model_names.append((name, app_label, model_name, data))
# Reset
model_names = postponed_model_names
# And perform the second run to iron out any circular/backwards depends.
self.retry_failed_fields()
# Force evaluation of relations on the models now
for model in self.models.values():
model._meta.get_all_field_names()
# Reset AppCache
hacks.unclear_app_cache()
def __iter__(self):
return iter(self.models.values())
def __getattr__(self, key):
fullname = (self.default_app+"."+key).lower()
try:
return self.models[fullname]
except KeyError:
raise AttributeError("The model '%s' from the app '%s' is not available in this migration. (Did you use orm.ModelName, not orm['app.ModelName']?)" % (key, self.default_app))
def __getitem__(self, key):
# Detect if they asked for a field on a model or not.
if ":" in key:
key, fname = key.split(":")
else:
fname = None
# Now, try getting the model
key = key.lower()
try:
model = self.models[key]
except KeyError:
try:
app, model = key.split(".", 1)
except ValueError:
raise KeyError("The model '%s' is not in appname.modelname format." % key)
else:
raise KeyError("The model '%s' from the app '%s' is not available in this migration." % (model, app))
# If they asked for a field, get it.
if fname:
return model._meta.get_field_by_name(fname)[0]
else:
return model
def eval_in_context(self, code, app, extra_imports={}):
"Evaluates the given code in the context of the migration file."
# Drag in the migration module's locals (hopefully including models.py)
# excluding all models from that (i.e. from modern models.py), to stop pollution
fake_locals = dict(
(key, value)
for key, value in inspect.getmodule(self.cls).__dict__.items()
if not (
isinstance(value, type)
and issubclass(value, models.Model)
and hasattr(value, "_meta")
)
)
# We add our models into the locals for the eval
fake_locals.update(dict([
(name.split(".")[-1], model)
for name, model in self.models.items()
]))
# Make sure the ones for this app override.
fake_locals.update(dict([
(name.split(".")[-1], model)
for name, model in self.models.items()
if name.split(".")[0] == app
]))
# Ourselves as orm, to allow non-fail cross-app referencing
fake_locals['orm'] = self
# And a fake _ function
fake_locals['_'] = lambda x: x
# Datetime; there should be no datetime direct accesses
fake_locals['datetime'] = datetime_utils
# Now, go through the requested imports and import them.
for name, value in extra_imports.items():
# First, try getting it out of locals.
parts = value.split(".")
try:
obj = fake_locals[parts[0]]
for part in parts[1:]:
obj = getattr(obj, part)
except (KeyError, AttributeError):
pass
else:
fake_locals[name] = obj
continue
# OK, try to import it directly
try:
fake_locals[name] = ask_for_it_by_name(value)
except ImportError:
if name == "SouthFieldClass":
raise ValueError("Cannot import the required field '%s'" % value)
else:
print("WARNING: Cannot import '%s'" % value)
# Use ModelsLocals to make lookups work right for CapitalisedModels
fake_locals = ModelsLocals(fake_locals)
return eval(code, globals(), fake_locals)
def make_meta(self, app, model, data, stub=False):
"Makes a Meta class out of a dict of eval-able arguments."
results = {'app_label': app}
for key, code in data.items():
# Some things we never want to use.
if key in ["_bases", "_ormbases"]:
continue
# Some things we don't want with stubs.
if stub and key in ["order_with_respect_to"]:
continue
# OK, add it.
try:
results[key] = self.eval_in_context(code, app)
except (NameError, AttributeError) as e:
raise ValueError("Cannot successfully create meta field '%s' for model '%s.%s': %s." % (
key, app, model, e
))
return type("Meta", tuple(), results)
def make_model(self, app, name, data):
"Makes a Model class out of the given app name, model name and pickled data."
# Extract any bases out of Meta
if "_ormbases" in data['Meta']:
# Make sure everything we depend on is done already; otherwise, wait.
for key in data['Meta']['_ormbases']:
key = key.lower()
if key not in self.models:
raise ORMBaseNotIncluded("Cannot find ORM base %s" % key)
elif isinstance(self.models[key], string_types):
# Then the other model hasn't been unfrozen yet.
# We postpone ourselves; the situation will eventually resolve.
raise UnfreezeMeLater()
bases = [self.models[key.lower()] for key in data['Meta']['_ormbases']]
# Perhaps the old style?
elif "_bases" in data['Meta']:
bases = map(ask_for_it_by_name, data['Meta']['_bases'])
# Ah, bog standard, then.
else:
bases = [models.Model]
# Turn the Meta dict into a basic class
meta = self.make_meta(app, name, data['Meta'], data.get("_stub", False))
failed_fields = {}
fields = {}
stub = False
# Now, make some fields!
for fname, params in data.items():
# If it's the stub marker, ignore it.
if fname == "_stub":
stub = bool(params)
continue
elif fname == "Meta":
continue
elif not params:
raise ValueError("Field '%s' on model '%s.%s' has no definition." % (fname, app, name))
elif isinstance(params, string_types):
# It's a premade definition string! Let's hope it works...
code = params
extra_imports = {}
else:
# If there's only one parameter (backwards compat), make it 3.
if len(params) == 1:
params = (params[0], [], {})
# There should be 3 parameters. Code is a tuple of (code, what-to-import)
if len(params) == 3:
code = "SouthFieldClass(%s)" % ", ".join(
params[1] +
["%s=%s" % (n, v) for n, v in params[2].items()]
)
extra_imports = {"SouthFieldClass": params[0]}
else:
raise ValueError("Field '%s' on model '%s.%s' has a weird definition length (should be 1 or 3 items)." % (fname, app, name))
try:
# Execute it in a probably-correct context.
field = self.eval_in_context(code, app, extra_imports)
except (NameError, AttributeError, AssertionError, KeyError):
# It might rely on other models being around. Add it to the
# model for the second pass.
failed_fields[fname] = (code, extra_imports)
else:
fields[fname] = field
# Find the app in the Django core, and get its module
more_kwds = {}
try:
app_module = models.get_app(app)
more_kwds['__module__'] = app_module.__name__
except ImproperlyConfigured:
# The app this belonged to has vanished, but thankfully we can still
# make a mock model, so ignore the error.
more_kwds['__module__'] = '_south_mock'
more_kwds['Meta'] = meta
# Make our model
fields.update(more_kwds)
model = type(
str(name),
tuple(bases),
fields,
)
# If this is a stub model, change Objects to a whiny class
if stub:
model.objects = WhinyManager()
# Also, make sure they can't instantiate it
model.__init__ = whiny_method
else:
model.objects = NoDryRunManager(model.objects)
if failed_fields:
model._failed_fields = failed_fields
return model
def retry_failed_fields(self):
"Tries to re-evaluate the _failed_fields for each model."
for modelkey, model in self.models.items():
app, modelname = modelkey.split(".", 1)
if hasattr(model, "_failed_fields"):
for fname, (code, extra_imports) in model._failed_fields.items():
try:
field = self.eval_in_context(code, app, extra_imports)
except (NameError, AttributeError, AssertionError, KeyError) as e:
# It's failed again. Complain.
raise ValueError("Cannot successfully create field '%s' for model '%s': %s." % (
fname, modelname, e
))
else:
# Startup that field.
model.add_to_class(fname, field)
class WhinyManager(object):
"A fake manager that whines whenever you try to touch it. For stub models."
def __getattr__(self, key):
raise AttributeError("You cannot use items from a stub model.")
class NoDryRunManager(object):
"""
A manager that always proxies through to the real manager,
unless a dry run is in progress.
"""
def __init__(self, real):
self.real = real
def __getattr__(self, name):
if db.dry_run:
raise AttributeError("You are in a dry run, and cannot access the ORM.\nWrap ORM sections in 'if not db.dry_run:', or if the whole migration is only a data migration, set no_dry_run = True on the Migration class.")
return getattr(self.real, name)
def whiny_method(*a, **kw):
raise ValueError("You cannot instantiate a stub model.")