partial_prepare incorrectly handles Django QueryDict, causes values to become lists

[slav0nic]

When using partial pipeline steps in Django projects, the partial_prepare function in social_core/pipeline/utils.py incorrectly converts QueryDict (and similar mapping types?) to a plain dict, causing all values to become lists. This breaks expected behavior: instead of scalar values, downstream code and extra_data receive lists (e.g. {"id": ["123"]} instead of {"id": "123"}).

Cause:

• The line value = dict(value) if is_dict_type(value) else value in partial_prepare loses the scalar/flat semantics. For QueryDict, dict(qd) always returns lists.

>>> from django.http.request import QueryDict
>>> d = QueryDict("a=1&b=2")
>>> dict(d)
{'a': ['1'], 'b': ['2']}
>>> d.dict()
{'a': '1', 'b': '2'}

Impact (observed in a Django app): After a partial pipeline resume, the backend (e.g. TelegramAuth) passes response straight to extra_data. Because response was turned into a plain dict with list values, the stored extra_data becomes:

Before partial (expected):

{
  "id": "123456789",
  "username": "demo_user",
  "first_name": "Alice",
  "hash": "<redacted_hash>"
}

After partial (actual):

{
  "id": ["123456789"],
  "username": ["demo_user"],
  "first_name": ["Alice"],
  "hash": ["<redacted_hash>"]
}

[nijel]

is_dict_type was apparently supposed to catch this:

social-core/social_core/pipeline/utils.py

Lines 4 to 11 in 5d98d92

	def is_dict_type(value):
	"""Treat any dict, MergeDict, MultiDict instance as dict type"""
	# Check by class name to avoid importing Django MergeDict or
	# Werkzeug MultiDict
	return isinstance(value, dict) or value.__class__.__name__ in (
	"MergeDict",
	"MultiDict",
	)

Maybe it no longer works with current Django version?

This most likely affects only a few backends that return query data as extra data (pocket and telegram showed up in a quick grep).

[slav0nic]

>>> d = QueryDict("a=1&b=2")
>>> is_dict_type(d)
True

as i said before, problem is here

social-core/social_core/pipeline/utils.py

Line 36 in 5d98d92

value = dict(value) if is_dict_type(value) else value

>>> dict(d)
{'a': ['1'], 'b': ['2']}

django.http.QueryDict.dict
method implementation django.utils.datastructures.MultiValueDict.dict()

Also django MergeDict was removed from 1.9 version