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