django/core/checks/model_checks.py
import inspect
import types
from collections import defaultdict
from itertools import chain
from django.apps import apps
from django.conf import settings
from django.core.checks import Error, Tags, Warning, register
@register(Tags.models)
def check_all_models(app_configs=None, **kwargs):
db_table_models = defaultdict(list)
indexes = defaultdict(list)
constraints = defaultdict(list)
errors = []
if app_configs is None:
models = apps.get_models()
else:
models = chain.from_iterable(
app_config.get_models() for app_config in app_configs
)
for model in models:
if model._meta.managed and not model._meta.proxy:
db_table_models[model._meta.db_table].append(model._meta.label)
if not inspect.ismethod(model.check):
errors.append(
Error(
"The '%s.check()' class method is currently overridden by %r."
% (model.__name__, model.check),
obj=model,
id="models.E020",
)
)
else:
errors.extend(model.check(**kwargs))
for model_index in model._meta.indexes:
indexes[model_index.name].append(model._meta.label)
for model_constraint in model._meta.constraints:
constraints[model_constraint.name].append(model._meta.label)
if settings.DATABASE_ROUTERS:
error_class, error_id = Warning, "models.W035"
error_hint = (
"You have configured settings.DATABASE_ROUTERS. Verify that %s "
"are correctly routed to separate databases."
)
else:
error_class, error_id = Error, "models.E028"
error_hint = None
for db_table, model_labels in db_table_models.items():
if len(model_labels) != 1:
model_labels_str = ", ".join(model_labels)
errors.append(
error_class(
"db_table '%s' is used by multiple models: %s."
% (db_table, model_labels_str),
obj=db_table,
hint=(error_hint % model_labels_str) if error_hint else None,
id=error_id,
)
)
for index_name, model_labels in indexes.items():
if len(model_labels) > 1:
model_labels = set(model_labels)
errors.append(
Error(
"index name '%s' is not unique %s %s."
% (
index_name,
"for model" if len(model_labels) == 1 else "among models:",
", ".join(sorted(model_labels)),
),
id="models.E029" if len(model_labels) == 1 else "models.E030",
),
)
for constraint_name, model_labels in constraints.items():
if len(model_labels) > 1:
model_labels = set(model_labels)
errors.append(
Error(
"constraint name '%s' is not unique %s %s."
% (
constraint_name,
"for model" if len(model_labels) == 1 else "among models:",
", ".join(sorted(model_labels)),
),
id="models.E031" if len(model_labels) == 1 else "models.E032",
),
)
return errors
def _check_lazy_references(apps, ignore=None):
"""
Ensure all lazy (i.e. string) model references have been resolved.
Lazy references are used in various places throughout Django, primarily in
related fields and model signals. Identify those common cases and provide
more helpful error messages for them.
The ignore parameter is used by StateApps to exclude swappable models from
this check.
"""
pending_models = set(apps._pending_operations) - (ignore or set())
# Short circuit if there aren't any errors.
if not pending_models:
return []
from django.db.models import signals
model_signals = {
signal: name
for name, signal in vars(signals).items()
if isinstance(signal, signals.ModelSignal)
}
def extract_operation(obj):
"""
Take a callable found in Apps._pending_operations and identify the
original callable passed to Apps.lazy_model_operation(). If that
callable was a partial, return the inner, non-partial function and
any arguments and keyword arguments that were supplied with it.
obj is a callback defined locally in Apps.lazy_model_operation() and
annotated there with a `func` attribute so as to imitate a partial.
"""
operation, args, keywords = obj, [], {}
while hasattr(operation, "func"):
args.extend(getattr(operation, "args", []))
keywords.update(getattr(operation, "keywords", {}))
operation = operation.func
return operation, args, keywords
def app_model_error(model_key):
try:
apps.get_app_config(model_key[0])
model_error = "app '%s' doesn't provide model '%s'" % model_key
except LookupError:
model_error = "app '%s' isn't installed" % model_key[0]
return model_error
# Here are several functions which return CheckMessage instances for the
# most common usages of lazy operations throughout Django. These functions
# take the model that was being waited on as an (app_label, modelname)
# pair, the original lazy function, and its positional and keyword args as
# determined by extract_operation().
def field_error(model_key, func, args, keywords):
error_msg = (
"The field %(field)s was declared with a lazy reference "
"to '%(model)s', but %(model_error)s."
)
params = {
"model": ".".join(model_key),
"field": keywords["field"],
"model_error": app_model_error(model_key),
}
return Error(error_msg % params, obj=keywords["field"], id="fields.E307")
def signal_connect_error(model_key, func, args, keywords):
error_msg = (
"%(receiver)s was connected to the '%(signal)s' signal with a "
"lazy reference to the sender '%(model)s', but %(model_error)s."
)
receiver = args[0]
# The receiver is either a function or an instance of class
# defining a `__call__` method.
if isinstance(receiver, types.FunctionType):
description = "The function '%s'" % receiver.__name__
elif isinstance(receiver, types.MethodType):
description = "Bound method '%s.%s'" % (
receiver.__self__.__class__.__name__,
receiver.__name__,
)
else:
description = "An instance of class '%s'" % receiver.__class__.__name__
signal_name = model_signals.get(func.__self__, "unknown")
params = {
"model": ".".join(model_key),
"receiver": description,
"signal": signal_name,
"model_error": app_model_error(model_key),
}
return Error(error_msg % params, obj=receiver.__module__, id="signals.E001")
def default_error(model_key, func, args, keywords):
error_msg = (
"%(op)s contains a lazy reference to %(model)s, but %(model_error)s."
)
params = {
"op": func,
"model": ".".join(model_key),
"model_error": app_model_error(model_key),
}
return Error(error_msg % params, obj=func, id="models.E022")
# Maps common uses of lazy operations to corresponding error functions
# defined above. If a key maps to None, no error will be produced.
# default_error() will be used for usages that don't appear in this dict.
known_lazy = {
("django.db.models.fields.related", "resolve_related_class"): field_error,
("django.db.models.fields.related", "set_managed"): None,
("django.dispatch.dispatcher", "connect"): signal_connect_error,
}
def build_error(model_key, func, args, keywords):
key = (func.__module__, func.__name__)
error_fn = known_lazy.get(key, default_error)
return error_fn(model_key, func, args, keywords) if error_fn else None
return sorted(
filter(
None,
(
build_error(model_key, *extract_operation(func))
for model_key in pending_models
for func in apps._pending_operations[model_key]
),
),
key=lambda error: error.msg,
)
@register(Tags.models)
def check_lazy_references(app_configs=None, **kwargs):
return _check_lazy_references(apps)