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Diffstat (limited to 'lib/python2.7/site-packages/south/orm.py')
| -rw-r--r-- | lib/python2.7/site-packages/south/orm.py | 407 |
1 files changed, 407 insertions, 0 deletions
diff --git a/lib/python2.7/site-packages/south/orm.py b/lib/python2.7/site-packages/south/orm.py new file mode 100644 index 0000000..8d46ee7 --- /dev/null +++ b/lib/python2.7/site-packages/south/orm.py @@ -0,0 +1,407 @@ +""" +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.") |