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# -*- coding: utf-8 -*-
from django.db import models
from django.db.models.fields import related
from mockups import constraints, generators, signals, factory
from mockups.helpers import get_mockup
class IGNORE_FIELD(object):
pass
class CreateInstanceError(Exception):
pass
class Link(object):
'''
Handles logic of following or generating foreignkeys and m2m relations.
'''
def __init__(self, fields=None, default=None):
self.fields = {}
self.subfields = {}
self.default = default
fields = fields or {}
if fields is True:
fields = {'ALL': None}
if not isinstance(fields, dict):
fields = dict([(v, None) for v in fields])
for field, value in fields.items():
try:
fieldname, subfield = field.split('__', 1)
self.subfields.setdefault(fieldname, {})[subfield] = value
except ValueError:
self.fields[field] = value
def __getitem__(self, key):
return self.fields.get(key,
self.fields.get('ALL', self.default))
def __iter__(self):
for field in self.fields:
yield field
for key, value in self.subfields.items():
yield '%s__%s' % (key, value)
def __contains__(self, value):
if 'ALL' in self.fields:
return True
if value in self.fields:
return True
return False
def get_deep_links(self, field):
if 'ALL' in self.fields:
fields = {'ALL': self.fields['ALL']}
else:
fields = self.subfields.get(field, {})
if 'ALL' in fields:
fields = {'ALL': fields['ALL']}
return Link(fields, default=self.default)
class Mockup(object):
'''
.. We don't support the following fields yet:
* ``XMLField``
* ``FileField``
* ``ImageField``
Patches are welcome.
'''
follow_fk = True
generate_fk = False
follow_m2m = {'ALL': (1,5)}
generate_m2m = False
creation_tries = 1000
default_constraints = [ constraints.unique_constraint,
constraints.unique_together_constraint]
factory = factory.Factory
def __init__(self, model, constraints=None, follow_fk=None,
generate_fk=None, follow_m2m=None, generate_m2m=None,
factory=None):
'''
Parameters:
``model``: A model class which is used to create the test data.
``constraints``: A list of callables. The constraints are used to
verify if the created model instance may be used. The callable
gets the actual model as first and the instance as second
parameter. The instance is not populated yet at this moment. The
callable may raise an :exc:`InvalidConstraint` exception to
indicate which fields violate the constraint.
``follow_fk``: A boolean value indicating if foreign keys should be
set to random, already existing, instances of the related model.
``generate_fk``: A boolean which indicates if related models should
also be created with random values. The *follow_fk* parameter will
be ignored if *generate_fk* is set to ``True``.
``follow_m2m``: A tuple containing minium and maximum of model
instances that are assigned to ``ManyToManyField``. No new
instances will be created. Default is (1, 5). You can ignore
``ManyToManyField`` fields by setting this parameter to ``False``.
``generate_m2m``: A tuple containing minimum and maximum number of
model instance that are newly created and assigned to the
``ManyToManyField``. Default is ``False`` which disables the
generation of new related instances. The value of ``follow_m2m``
will be ignored if this parameter is set.
``factory``: A Factory *instance*, overriding the one defined in the
Mockup class.
'''
self.model = model
self.constraints = constraints or []
# instantiate the factory class
if factory is not None:
self.factory = factory.__class__
self._factory = factory
else:
self._factory = self.factory()
if follow_fk is not None:
self.follow_fk = follow_fk
if not isinstance(self.follow_fk, Link):
self.follow_fk = Link(self.follow_fk)
if generate_fk is not None:
self.generate_fk = generate_fk
if not isinstance(self.generate_fk, Link):
self.generate_fk = Link(self.generate_fk)
if follow_m2m is not None:
if not isinstance(follow_m2m, dict):
if follow_m2m:
follow_m2m = Link({'ALL': follow_m2m})
else:
follow_m2m = Link(False)
self.follow_m2m = follow_m2m
if not isinstance(self.follow_m2m, Link):
self.follow_m2m = Link(self.follow_m2m)
if generate_m2m is not None:
if not isinstance(generate_m2m, dict):
if generate_m2m:
generate_m2m = Link({'ALL': generate_m2m})
else:
generate_m2m = Link(False)
self.generate_m2m = generate_m2m
if not isinstance(self.generate_m2m, Link):
self.generate_m2m = Link(self.generate_m2m)
for constraint in self.default_constraints:
self.add_constraint(constraint)
self._fieldname_to_generator = {}
self.prepare_class()
def prepare_class(self):
'''
This method is called after the :meth:`__init__` method. It has no
semantic by default.
'''
pass
def update_fieldname_generator(self, **kwargs):
'''
Updates the factory instance with new generators
'''
self._factory.fieldname_to_generator.update(kwargs)
def add_constraint(self, constraint):
'''
Add a *constraint* to the mockup.
'''
self.constraints.append(constraint)
def get_generator(self, field):
'''
Return a value generator based on the field instance that is passed to
this method. This function may return ``None`` which means that the
specified field will be ignored (e.g. if no matching generator was
found).
'''
params = {
'follow_fk': self.follow_fk,
'generate_fk': self.generate_fk,
'follow_m2m': self.follow_m2m,
'generate_m2m': self.generate_m2m,
}
return self._factory.get_generator(field, **params)
def get_value(self, field):
'''
Return a random value that can be assigned to the passed *field*
instance.
'''
if field not in self._fieldname_to_generator:
self._fieldname_to_generator[field] = self.get_generator(field)
generator = self._fieldname_to_generator[field]
if generator is None:
return IGNORE_FIELD
return generator.get_value()
def process_field(self, instance, field):
value = self.get_value(field)
if value is not IGNORE_FIELD:
setattr(instance, field.name, value)
def process_m2m(self, instance, field):
# check django's version number to determine how intermediary models
# are checked if they are auto created or not.
from django import VERSION
auto_created_through_model = False
through = field.rel.through
if VERSION < (1, 2):
if through:
if isinstance(through, basestring):
bits = through.split('.')
if len(bits) < 2:
bits = [instance._meta.app_label] + bits
through = models.get_model(*bits)
else:
auto_created_through_model = True
else:
auto_created_through_model = through._meta.auto_created
if auto_created_through_model:
return self.process_field(instance, field)
# if m2m relation has intermediary model:
# * only generate relation if 'generate_m2m' is given
# * first generate intermediary model and assign a newly created
# related model to the foreignkey
if field.name in self.generate_m2m:
# get fk to related model on intermediary model
related_fks = [fk
for fk in through._meta.fields
if isinstance(fk, related.ForeignKey) and \
fk.rel.to is field.rel.to]
self_fks = [fk
for fk in through._meta.fields
if isinstance(fk, related.ForeignKey) and \
fk.rel.to is self.model]
assert len(related_fks) == 1
assert len(self_fks) == 1
related_fk = related_fks[0]
self_fk = self_fks[0]
min_count, max_count = self.generate_m2m[field.name]
related_mockup = get_mockup(field.rel.to)
related_generator = generators.InstanceGenerator(related_mockup)
through_mockup = get_mockup(through)
# update the through mockup factory
params = {
self_fk.name: generators.StaticGenerator(instance),
related_fk.name: generators.InstanceGenerator(related_mockup),
}
through_mockup.update_fieldname_generator(**params)
generator = generators.MultipleInstanceGenerator(through_mockup,
min_count=min_count, max_count=max_count)
generator.generate()
def check_constrains(self, instance):
'''
Return fieldnames which need recalculation.
'''
recalc_fields = []
for constraint in self.constraints:
try:
constraint(self.model, instance)
except constraints.InvalidConstraint, e:
recalc_fields.extend(e.fields)
return recalc_fields
def post_process_instance(self, instance):
'''
Overwrite this method to modify the created *instance* at the last
possible moment. It gets the generated *instance* and must return the
modified instance.
'''
return instance
def create_one(self, commit=True):
'''
Create and return one model instance. If *commit* is ``False`` the
instance will not be saved and many to many relations will not be
processed.
May raise :exc:`CreateInstanceError` if constraints are not satisfied.
'''
creation_tries = self.creation_tries
instance = self.model()
process = instance._meta.fields
while process and creation_tries > 0:
for field in process:
self.process_field(instance, field)
process = self.check_constrains(instance)
creation_tries -= 1
if creation_tries == 0:
raise CreateInstanceError(
u'Cannot solve constraints for "%s", tried %d times. '
u'Please check value generators or model constraints. '
u'At least the following fields are involved: %s' % (
'%s.%s' % (
self.model._meta.app_label,
self.model._meta.object_name),
self.creation_tries,
', '.join([field.name for field in process]),
))
if commit:
instance.save()
for field in instance._meta.many_to_many:
self.process_m2m(instance, field)
signals.instance_created.send(
sender=self,
model=self.model,
instance=instance,
committed=commit)
return self.post_process_instance(instance)
def create(self, count=1, commit=True):
'''
Create and return ``count`` model instances. If *commit* is ``False``
the instances will not be saved and many to many relations will not be
processed.
May raise ``CreateInstanceError`` if constraints are not satisfied.
The method internally calls :meth:`create_one` to generate instances.
'''
object_list = []
for i in xrange(count):
instance = self.create_one(commit=commit)
object_list.append(instance)
return object_list
def iter(self, count=1, commit=True):
for i in xrange(count):
yield self.create_one(commit=commit)
def __iter__(self):
yield self.create_one()