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# Copyright (c) 2010 Mark Sandstrom
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import re
import sys
from containers import AttributeBuilder, DeclarationDict, ObjectParamsWrapper, StubObject
from declarations import OrderedDeclaration
# Strategies
BUILD_STRATEGY = 'build'
CREATE_STRATEGY = 'create'
STUB_STRATEGY = 'stub'
# Creation functions. Use Factory.set_creation_function() to set a creation function appropriate for your ORM.
DJANGO_CREATION = lambda class_to_create, **kwargs: class_to_create.objects.create(**kwargs)
# Special declarations
FACTORY_CLASS_DECLARATION = 'FACTORY_FOR'
# Factory class attributes
CLASS_ATTRIBUTE_DECLARATIONS = '_declarations'
CLASS_ATTRIBUTE_ASSOCIATED_CLASS = '_associated_class'
# Factory metaclasses
def get_factory_base(bases):
return [b for b in bases if isinstance(b, BaseFactoryMetaClass)]
class BaseFactoryMetaClass(type):
"""Factory metaclass for handling ordered declarations."""
def __call__(cls, **kwargs):
"""Create an associated class instance using the default build strategy. Never create a Factory instance."""
if cls.default_strategy == BUILD_STRATEGY:
return cls.build(**kwargs)
elif cls.default_strategy == CREATE_STRATEGY:
return cls.create(**kwargs)
elif cls.default_strategy == STUB_STRATEGY:
return cls.stub(**kwargs)
else:
raise BaseFactory.UnknownStrategy('Unknown default_strategy: {0}'.format(cls.default_strategy))
def __new__(cls, class_name, bases, attrs, extra_attrs={}):
"""Record attributes (unordered declarations) and ordered declarations for construction of
an associated class instance at a later time."""
parent_factories = get_factory_base(bases)
if not parent_factories or attrs.get('ABSTRACT_FACTORY', False):
# If this isn't a subclass of Factory, don't do anything special.
return super(BaseFactoryMetaClass, cls).__new__(cls, class_name, bases, attrs)
declarations = DeclarationDict()
#Add parent declarations in reverse order.
for base in reversed(parent_factories):
declarations.update_with_public(getattr(base, CLASS_ATTRIBUTE_DECLARATIONS, {}))
non_factory_attrs = declarations.update_with_public(attrs)
non_factory_attrs[CLASS_ATTRIBUTE_DECLARATIONS] = declarations
non_factory_attrs.update(extra_attrs)
return super(BaseFactoryMetaClass, cls).__new__(cls, class_name, bases, non_factory_attrs)
class FactoryMetaClass(BaseFactoryMetaClass):
"""Factory metaclass for handling class association and ordered declarations."""
ERROR_MESSAGE = """Could not determine what class this factory is for.
Use the {0} attribute to specify a class."""
ERROR_MESSAGE_AUTODISCOVERY = ERROR_MESSAGE + """
Also, autodiscovery failed using the name '{1}'
based on the Factory name '{2}' in {3}."""
def __new__(cls, class_name, bases, attrs):
"""Determine the associated class based on the factory class name. Record the associated class
for construction of an associated class instance at a later time."""
parent_factories = get_factory_base(bases)
if not parent_factories or attrs.get('ABSTRACT_FACTORY', False):
# If this isn't a subclass of Factory, don't do anything special.
return super(FactoryMetaClass, cls).__new__(cls, class_name, bases, attrs)
base = parent_factories[0]
inherited_associated_class = getattr(base, CLASS_ATTRIBUTE_ASSOCIATED_CLASS, None)
own_associated_class = None
used_auto_discovery = False
if FACTORY_CLASS_DECLARATION in attrs:
own_associated_class = attrs.pop(FACTORY_CLASS_DECLARATION)
else:
factory_module = sys.modules[attrs['__module__']]
match = re.match(r'^(\w+)Factory$', class_name)
if match:
used_auto_discovery = True
associated_class_name = match.group(1)
try:
own_associated_class = getattr(factory_module, associated_class_name)
except AttributeError:
pass
if own_associated_class is None and inherited_associated_class is not None:
own_associated_class = inherited_associated_class
attrs['_base_factory'] = base
if not own_associated_class:
if used_auto_discovery:
format_args = FACTORY_CLASS_DECLARATION, associated_class_name, class_name, factory_module
raise Factory.AssociatedClassError(FactoryMetaClass.ERROR_MESSAGE_AUTODISCOVERY.format(*format_args))
else:
raise Factory.AssociatedClassError(FactoryMetaClass.ERROR_MESSAGE.format(FACTORY_CLASS_DECLARATION))
extra_attrs = {CLASS_ATTRIBUTE_ASSOCIATED_CLASS: own_associated_class}
return super(FactoryMetaClass, cls).__new__(cls, class_name, bases, attrs, extra_attrs=extra_attrs)
# Factory base classes
class BaseFactory(object):
"""Factory base support for sequences, attributes and stubs."""
class UnknownStrategy(RuntimeError): pass
class UnsupportedStrategy(RuntimeError): pass
def __new__(cls, *args, **kwargs):
raise RuntimeError('You cannot instantiate BaseFactory')
_next_sequence = None
_base_factory = None
@classmethod
def _setup_next_sequence(cls):
"""Set up an initial sequence value for Sequence attributes."""
return 0
@classmethod
def _generate_next_sequence(cls):
if cls._base_factory:
return cls._base_factory._generate_next_sequence()
if cls._next_sequence is None:
cls._next_sequence = cls._setup_next_sequence()
next_sequence = cls._next_sequence
cls._next_sequence += 1
return next_sequence
@classmethod
def attributes(cls, create=False, extra=None):
"""Build a dict of attribute values, respecting declaration order.
The process is:
- Handle 'orderless' attributes, overriding defaults with provided
kwargs when applicable
- Handle ordered attributes, overriding them with provided kwargs when
applicable; the current list of computed attributes is available
to the currently processed object.
"""
return AttributeBuilder(cls, extra).build(create)
@classmethod
def declarations(cls, extra_defs=None):
return getattr(cls, CLASS_ATTRIBUTE_DECLARATIONS).copy(extra_defs)
@classmethod
def build(cls, **kwargs):
raise cls.UnsupportedStrategy()
@classmethod
def create(cls, **kwargs):
raise cls.UnsupportedStrategy()
@classmethod
def stub(cls, **kwargs):
stub_object = StubObject()
for name, value in cls.attributes(**kwargs).iteritems():
setattr(stub_object, name, value)
return stub_object
class StubFactory(BaseFactory):
__metaclass__ = BaseFactoryMetaClass
default_strategy = STUB_STRATEGY
class Factory(BaseFactory):
"""Factory base with build and create support.
This class has the ability to support multiple ORMs by using custom creation functions."""
__metaclass__ = FactoryMetaClass
default_strategy = CREATE_STRATEGY
class AssociatedClassError(RuntimeError): pass
_creation_function = (DJANGO_CREATION,) # Using a tuple to keep the creation function from turning into an instance method
@classmethod
def set_creation_function(cls, creation_function):
cls._creation_function = (creation_function,)
@classmethod
def get_creation_function(cls):
return cls._creation_function[0]
@classmethod
def _prepare(cls, create, **kwargs):
"""Prepare an object for this factory.
Args:
create: bool, whether to create or to build the object
**kwargs: arguments to pass to the creation function
"""
if create:
return cls.get_creation_function()(getattr(cls, CLASS_ATTRIBUTE_ASSOCIATED_CLASS), **kwargs)
else:
return getattr(cls, CLASS_ATTRIBUTE_ASSOCIATED_CLASS)(**kwargs)
@classmethod
def _build(cls, **kwargs):
return cls._prepare(create=False, **kwargs)
@classmethod
def _create(cls, **kwargs):
return cls._prepare(create=True, **kwargs)
@classmethod
def build(cls, **kwargs):
return cls._build(**cls.attributes(create=False, extra=kwargs))
@classmethod
def create(cls, **kwargs):
return cls._create(**cls.attributes(create=True, extra=kwargs))
class DjangoModelFactory(Factory):
"""Factory for django models.
This makes sure that the 'sequence' field of created objects is an unused id.
Possible improvement: define a new 'attribute' type, AutoField, which would
handle those for non-numerical primary keys.
"""
ABSTRACT_FACTORY = True
@classmethod
def _setup_next_sequence(cls):
try:
return cls._associated_class.objects.values_list('id', flat=True).order_by('-id')[0] + 1
except IndexError:
return 1
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