[Django] #36833: HttpRequest.accepted_types incorrectly splits Accept header on commas inside quoted parameter values

[Django]

#36833: HttpRequest.accepted_types incorrectly splits Accept header on commas
inside quoted parameter values
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Reporter: Naveed Qadir | Owner: Naveed Qadir
Type: Bug | Status: assigned
Component: HTTP handling | Version: dev
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 1
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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The `accepted_types` property in `HttpRequest` uses `str.split(",")` to
parse the Accept header, which incorrectly splits on commas that appear
inside quoted parameter values.

== Example ==

{{{#!python
# Accept header with quoted parameter containing comma
header = 'text/plain; param="a,b", application/json'

# Current behavior (WRONG):
header.split(",")
# Returns: ['text/plain; param="a', 'b"', ' application/json']
# 3 parts - comma inside quotes was incorrectly treated as separator

# Expected behavior (per RFC 7231):
# Should return 2 media types:
# 1. text/plain; param="a,b"
# 2. application/json
}}}

== RFC Reference ==

RFC 7231 Section 5.3.2 specifies that media-type parameters can contain
quoted-string values, and RFC 7230 Section 3.2.6 allows commas within
quoted strings.

== Proposed Fix ==

Add a `split_header_words()` helper function to `django/utils/http.py`
that splits on commas while respecting quoted strings, similar to how
`_parseparam()` handles semicolons.

A patch with tests is available.
--
Ticket URL: <https://code.djangoproject.com/ticket/36833>
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