Automatic handling of OPTIONS during POST

[AdrianTeng]

Say I have a route that expects some json POST body:

@view_config(route_name='foo', renderer='json')
def foo(request):
    return fancy_transform(request.json_body)

It works all and well in a standard scenario, as shown in the documentation here. But if you are doing a Cross-Origin Resource Sharing, then the standard is to first run a OPTIONS request to get server's approval, then execute the POST request.

In my particular case, I'm using AngularJS's $http to run POST with some json body onto the route foo. AngularJS then first run a OPTIONS, which has no body, and the route return a 500, since request.json_body fails to decode empty body.

There are currently few workaround:

• Make function foo only handles request_method='POST', add another function that has same route_name and handle request_method='OPTIONS'. The extra function can return an empty dict. Alternatively just extend function foo to handle cases with different request_method
• On AngularJS, use customised header {'Content-Type': 'application/x-www-form-urlencoded'}. This will make $http skipping OPTIONS and go straight into POST

I feel the handling of OPTIONS request should be done by Pyramid automatically.

[tseaver]

The OPTIONS method is sent as part of a CORS preflighted request. Pyramid cannot handle it automatically, because it involves application policy (what headers to set on the response). This issue needs to be addressed by a custom decorator (defined in your app) or a higher-level framework (e.g., Cornice or rest-toolkit).

[digitalresistor]

@AdrianTeng Your first "workaround" is actually the only and correct answer for Pyramid.

[AdrianTeng]

@tseaver Fair enough, but I think this is worth documenting. I'll add some examples to here later.