def get_task_type(job=None,
file_cacher=None,
dataset=None,
task_type_name=None):
"""Given a job, instantiate the corresponding TaskType class.
job (Job): the job to perform.
file_cacher (FileCacher): a file cacher object.
dataset (Dataset): if we don't want to grade, but just to get
information, we can provide only the
dataset and not the submission.
task_type_name (string): again, if we only need the class, we can
give only the task type name.
return (object): an instance of the correct TaskType class.
"""
# Validate arguments.
if [x is not None
for x in [job, dataset, task_type_name]].count(True) != 1:
raise ValueError("Need exactly one way to get the task type.")
elif [x is not None for x in [job, file_cacher]].count(True) not in [0, 2]:
raise ValueError("Need file cacher to perform a job.")
# Recover information from the arguments.
task_type_parameters = None
if job is not None:
task_type_name = job.task_type
if dataset is not None:
task_type_name = dataset.task_type
try:
task_type_parameters = json.loads(dataset.task_type_parameters)
except json.decoder.JSONDecodeError as error:
logger.error("Cannot decode task type parameters.\n%r." % error)
raise
job = Job()
job.task_type = task_type_name
job.task_type_parameters = task_type_parameters
cls = plugin_lookup(task_type_name, "cms.grading.tasktypes", "tasktypes")
return cls(job, file_cacher)
