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from rest_framework import exceptions
from rest_framework.settings import api_settings
from rest_framework.utils.mediatypes import order_by_precedence, media_type_matches
class BaseContentNegotiation(object):
def negotiate(self, request, renderers, format=None, force=False):
raise NotImplementedError('.negotiate() must be implemented')
class DefaultContentNegotiation(object):
settings = api_settings
def negotiate(self, request, renderers, format=None, force=False):
"""
Given a request and a list of renderers, return a two-tuple of:
(renderer, media type).
If force is set, then suppress exceptions, and forcibly return a
fallback renderer and media_type.
"""
try:
return self.unforced_negotiate(request, renderers, format)
except (exceptions.InvalidFormat, exceptions.NotAcceptable):
if force:
return (renderers[0], renderers[0].media_type)
raise
def unforced_negotiate(self, request, renderers, format=None):
"""
As `.negotiate()`, but does not take the optional `force` agument,
or suppress exceptions.
"""
# Allow URL style format override. eg. "?format=json
format = format or request.GET.get(self.settings.URL_FORMAT_OVERRIDE)
if format:
renderers = self.filter_renderers(renderers, format)
accepts = self.get_accept_list(request)
# Check the acceptable media types against each renderer,
# attempting more specific media types first
# NB. The inner loop here isn't as bad as it first looks :)
# Worst case is we're looping over len(accept_list) * len(self.renderers)
for media_type_set in order_by_precedence(accepts):
for renderer in renderers:
for media_type in media_type_set:
if media_type_matches(renderer.media_type, media_type):
# Return the most specific media type as accepted.
if len(renderer.media_type) > len(media_type):
# Eg client requests '*/*'
# Accepted media type is 'application/json'
return renderer, renderer.media_type
else:
# Eg client requests 'application/json; indent=8'
# Accepted media type is 'application/json; indent=8'
return renderer, media_type
raise exceptions.NotAcceptable(available_renderers=renderers)
def filter_renderers(self, renderers, format):
"""
If there is a '.json' style format suffix, filter the renderers
so that we only negotiation against those that accept that format.
"""
renderers = [renderer for renderer in renderers
if renderer.format == format]
if not renderers:
raise exceptions.InvalidFormat(format)
return renderers
def get_accept_list(self, request):
"""
Given the incoming request, return a tokenised list of media
type strings.
Allows URL style accept override. eg. "?accept=application/json"
"""
header = request.META.get('HTTP_ACCEPT', '*/*')
header = request.GET.get(self.settings.URL_ACCEPT_OVERRIDE, header)
return [token.strip() for token in header.split(',')]
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