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patch_handler.py
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Thu, Dec 12, 9:39 AM

patch_handler.py

"""Handler for PATCH requests.
This supports PATCH request in the sense described by William Durand:
http://williamdurand.fr/2014/02/14/please-do-not-patch-like-an-idiot/
Each PATCH should be a JSON dict with at least a key 'op' with the
name of the operation to perform.
"""
import logging
import flask
from pillar.api.utils import authorization
log = logging.getLogger(__name__)
class AbstractPatchHandler:
"""Abstract PATCH handler supporting multiple operations.
Each operation, i.e. possible value of the 'op' key in the PATCH body,
should be matched to a similarly named "patch_xxx" function in a subclass.
For example, the operation "set-owner" is mapped to "patch_set_owner".
:cvar route: the Flask/Werkzeug route to attach this handler to.
For most handlers, the default will be fine.
:cvar item_name: the name of the things to patch, like "job", "task" etc.
Only used for logging.
"""
route: str = '/<object_id>'
item_name: str = None
def __init_subclass__(cls, **kwargs):
if not cls.route:
raise ValueError('Subclass must set route')
if not cls.item_name:
raise ValueError('Subclass must set item_name')
def __init__(self, blueprint: flask.Blueprint):
self.log: logging.Logger = log.getChild(self.__class__.__name__)
self.patch_handlers = {
name[6:].replace('_', '-'): getattr(self, name)
for name in dir(self)
if name.startswith('patch_') and callable(getattr(self, name))
}
if self.log.isEnabledFor(logging.INFO):
self.log.info('Creating PATCH handler %s.%s%s for operations: %s',
blueprint.name, self.patch.__name__, self.route,
sorted(self.patch_handlers.keys()))
blueprint.add_url_rule(self.route,
self.patch.__name__,
self.patch,
methods=['PATCH'])
@authorization.require_login()
def patch(self, object_id: str):
from flask import request
import werkzeug.exceptions as wz_exceptions
from pillar.api.utils import str2id, authentication
# Parse the request
real_object_id = str2id(object_id)
patch = request.get_json()
if not patch:
self.log.info('Bad PATCH request, did not contain JSON')
raise wz_exceptions.BadRequest('Patch must contain JSON')
try:
patch_op = patch['op']
except KeyError:
self.log.info("Bad PATCH request, did not contain 'op' key")
raise wz_exceptions.BadRequest("PATCH should contain 'op' key to denote operation.")
log.debug('User %s wants to PATCH "%s" %s %s',
authentication.current_user_id(), patch_op, self.item_name, real_object_id)
# Find the PATCH handler for the operation.
try:
handler = self.patch_handlers[patch_op]
except KeyError:
log.warning('No %s PATCH handler for operation %r', self.item_name, patch_op)
raise wz_exceptions.BadRequest('Operation %r not supported' % patch_op)
# Let the PATCH handler do its thing.
response = handler(real_object_id, patch)
if response is None:
return '', 204
return response

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