#36447: HttpRequest.get_preferred_type misorders types when more specific
accepted
types have lower q
-------------------------------------+-------------------------------------
Reporter: Anders Kaseorg | Owner: Jake
| Howard
Type: Bug | Status: assigned
Component: HTTP handling | Version: 5.2
Severity: Release blocker | Resolution:
Keywords: preferred media | Triage Stage: Accepted
type |
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by Anders Kaseorg:
Old description:
> Consider this example from [https://www.rfc-
> editor.org/rfc/rfc9110.html#section-12.5.1-18 RFC 9110 §12.5.1]:
>
> The media type quality factor associated with a given type is
> determined by finding the media range with the highest precedence that
> matches the type. For example,
> {{{
> Accept: text/*;q=0.3, text/plain;q=0.7, text/plain;format=flowed,
> text/plain;format=fixed;q=0.4, */*;q=0.5
> }}}
> would cause the following values to be associated:
> ||= Media Type =||= Quality Value =||
> || text/plain;format=flowed || 1 ||
> || text/plain || 0.7 ||
> || text/html || 0.3 ||
> || image/jpeg || 0.5 ||
> || text/plain;format=fixed || 0.4 ||
> || text/html;level=3 || 0.7 ||
>
> Django’s `HttpRequest.get_preferred_type` fails to match this behavior.
>
> {{{
> >>> from django.conf import settings
> >>> from django.http import HttpRequest
> >>> settings.configure()
> >>> request = HttpRequest()
> >>> request.META["HTTP_ACCEPT"] = "text/*;q=0.3, text/plain;q=0.7,
> text/plain;format=flowed, text/plain;format=fixed;q=0.4, */*;q=0.5"
> >>> request.get_preferred_type(['text/plain', 'text/plain;format=fixed'])
> # expected text/plain (0.7 > 0.4)
> 'text/plain;format=fixed'
> >>> request.get_preferred_type(['text/html', 'image/jpeg']) # expected
> image/jpeg (0.3 < 0.5)
> 'text/html'
> >>> request.get_preferred_type(['text/html', 'text/html;level=3']) #
> expected text/html;level=3 (0.3 < 0.7)
> 'text/html'
> >>> request.get_preferred_type(['image/jpeg', 'text/html']) # expected
> image/jpeg (0.5 > 0.3)
> 'text/html'
> >>> request.get_preferred_type(['image/jpeg', 'text/plain;format=fixed'])
> # expected image/jpeg (0.5 > 0.4)
> 'text/plain;format=fixed'
> >>> request.get_preferred_type(['text/plain;format=fixed', 'text/plain'])
> # expected text/plain (0.4 < 0.7)
> 'text/plain;format=fixed'
> >>> request.get_preferred_type(['text/plain;format=fixed', 'image/jpeg'])
> # expected image/jpeg (0.4 < 0.5)
> 'text/plain;format=fixed'
> >>> request.get_preferred_type(['text/plain;format=fixed',
> 'text/html;level=3']) # expected text/html;level=3 (0.4 < 0.7)
> 'text/plain;format=fixed'
> >>> request.get_preferred_type(['text/html;level=3',
> 'text/plain;format=fixed']) # expected text/html;level=3 (0.7 > 0.4)
> 'text/plain;format=fixed'
> }}}
New description:
Consider this example from [https://www.rfc-
editor.org/rfc/rfc9110.html#section-12.5.1-18 RFC 9110 §12.5.1] (adjusted
for [https://www.rfc-editor.org/errata/eid7138 erratum 7138]):
The media type quality factor associated with a given type is determined
by finding the media range with the highest precedence that matches the
type. For example,
{{{
Accept: text/*;q=0.3, text/plain;q=0.7, text/plain;format=flowed,
text/plain;format=fixed;q=0.4, */*;q=0.5
}}}
would cause the following values to be associated:
||= Media Type =||= Quality Value =||
|| text/plain;format=flowed || 1 ||
|| text/plain || 0.7 ||
|| text/html || 0.3 ||
|| image/jpeg || 0.5 ||
|| text/plain;format=fixed || 0.4 ||
|| text/html;level=3 || 0.3 ||
Django’s `HttpRequest.get_preferred_type` fails to match this behavior.
{{{
>>> from django.conf import settings
>>> from django.http import HttpRequest
>>> settings.configure()
>>> request = HttpRequest()
>>> request.META["HTTP_ACCEPT"] = "text/*;q=0.3, text/plain;q=0.7,
text/plain;format=flowed, text/plain;format=fixed;q=0.4, */*;q=0.5"
>>> request.get_preferred_type(['text/plain', 'text/plain;format=fixed'])
# expected text/plain (0.7 > 0.4)
'text/plain;format=fixed'
>>> request.get_preferred_type(['text/html', 'image/jpeg']) # expected
image/jpeg (0.3 < 0.5)
'text/html'
>>> request.get_preferred_type(['image/jpeg', 'text/html']) # expected
image/jpeg (0.5 > 0.3)
'text/html'
>>> request.get_preferred_type(['image/jpeg', 'text/plain;format=fixed'])
# expected image/jpeg (0.5 > 0.4)
'text/plain;format=fixed'
>>> request.get_preferred_type(['image/jpeg', 'text/html;level=3']) #
expected image/jpeg (0.5 > 0.3)
'text/html;level=3'
>>> request.get_preferred_type(['text/plain;format=fixed', 'text/plain'])
# expected text/plain (0.4 < 0.7)
'text/plain;format=fixed'
>>> request.get_preferred_type(['text/plain;format=fixed', 'image/jpeg'])
# expected image/jpeg (0.4 < 0.5)
'text/plain;format=fixed'
>>> request.get_preferred_type(['text/html;level=3', 'image/jpeg']) #
expected image/jpeg (0.3 < 0.5)
'text/html;level=3'
}}}
--
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Ticket URL: <https://code.djangoproject.com/ticket/36447#comment:9>
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