def to_python(self, value):
"""Return a ProjectSignature value from the field contents.
Args:
value (object):
The current value assigned to the field. This might be
serialized string content or a
:py:class:`~django_evolution.signatures.ProjectSignature`
instance.
Returns:
django_evolution.signatures.ProjectSignature:
The project signature stored in the field.
Raises:
django.core.exceptions.ValidationError:
The field contents are of an unexpected type.
"""
if isinstance(value, six.string_types):
if value.startswith('json!'):
loaded_value = json.loads(value[len('json!'):],
object_pairs_hook=OrderedDict)
else:
loaded_value = pickle_loads(value)
return ProjectSignature.deserialize(loaded_value)
elif isinstance(value, ProjectSignature):
return value
else:
raise ValidationError(
'Unsupported serialized signature type %s' % type(value),
code='invalid',
params={
'value': value,
})
def to_python(self, value):
"""Return a ProjectSignature value from the field contents.
Args:
value (object):
The current value assigned to the field. This might be
serialized string content or a
:py:class:`~django_evolution.signatures.ProjectSignature`
instance.
Returns:
django_evolution.signatures.ProjectSignature:
The project signature stored in the field.
Raises:
django.core.exceptions.ValidationError:
The field contents are of an unexpected type.
"""
if isinstance(value, six.string_types):
return ProjectSignature.deserialize(pickle_loads(value))
elif isinstance(value, ProjectSignature):
return value
else:
raise ValidationError('Unsupported serialized signature type %s' %
type(value),
code='invalid',
params={
'value': value,
})
def simulate(self, simulation):
"""Simulate a mutation for an application.
This will run the :py:attr:`update_func` provided when instantiating
the mutation, passing it ``app_label`` and ``project_sig``. It should
then modify the signature to match what the SQL statement would do.
Args:
simulation (Simulation):
The state for the simulation.
Raises:
django_evolution.errors.CannotSimulate:
:py:attr:`update_func` was not provided or was not a function.
django_evolution.errors.SimulationFailure:
The simulation failed. The reason is in the exception's
message. This would be run by :py:attr:`update_func`.
"""
if callable(self.update_func):
if hasattr(inspect, 'getfullargspec'):
# Python 3
argspec = inspect.getfullargspec(self.update_func)
else:
# Python 2
argspec = inspect.getargspec(self.update_func)
if len(argspec.args) == 1 and argspec.args[0] == 'simulation':
# New-style simulation function.
self.update_func(simulation)
return
elif len(argspec.args) == 2:
# Legacy simulation function.
project_sig = simulation.project_sig
serialized_sig = project_sig.serialize(sig_version=1)
self.update_func(simulation.app_label, serialized_sig)
new_project_sig = ProjectSignature.deserialize(serialized_sig)
# We have to reconstruct the existing project signature's state
# based on this.
app_sig_ids = [
app_sig.app_id for app_sig in new_project_sig.app_sigs
]
for app_sig_id in app_sig_ids:
project_sig.remove_app_sig(app_sig_id)
for app_sig in new_project_sig.app_sigs:
project_sig.add_app_sig(app_sig)
return
raise CannotSimulate(
'SQLMutations must provide an update_func(simulation) or '
'legacy update_func(app_label, project_sig) parameter '
'in order to be simulated.')
