twilio/flask-restful — pull request #270 by gdbelvin (2014-07-11 06:05:52+00:00)
Title: Update reqparse.clone to make a deep copy of the arglist.

self.put_parser = parser.copy()
self.post_parser = parser.copy()
self.post_parser.replace_argument('email', type = str, required = True, location = 'json')

In this example, the change to post_parse, pollutes the arguments in put_parser because, underneath, both put_parser and post_parser point to the same argument list.

Inserting list() creates a new, distinct list object, and solves the issue.