Unexpected behavior for django.utils.http.urlencode

[Johan Lübcke]

The function django.utils.http.urlencode has been changed to give unexpected result for tuple values (and other iterable objects) in the case when no iterations is expected:

>>> django.utils.http.urlencode(dict(a=('a','b')), doseq=False)
'a=%5B%27a%27%2C+%27b%27%5D'

One would expect the same as the standard library version (Note the first and last characters has been replaced by square brackets):

>>> urllib.parse.urlencode(dict(a=('a', 'b')), doseq=False)
'a=%28%27a%27%2C+%27b%27%29'

If the value is a list, the result if what one would expect:

>>> django.utils.http.urlencode(dict(a=['a','b']), doseq=False)
'a=%5B%27a%27%2C+%27b%27%5D'
>>> urllib.parse.urlencode(dict(a=['a', 'b']), doseq=False)
'a=%5B%27a%27%2C+%27b%27%5D'

Note: This is a problem when one has objects that has a __str__ method defined, returning the value one would want to be in the urlencode result, but the object by coincidence is also iterable.

[Carlton Gibson]

Asking François to comment. This is related to #28679.

[Carlton Gibson]

OK, having conferred with Mariusz, I'm going to Accept this as a bug on 2.2, to be fixed in master, rather than backported to 2.2. (We'll look at the final patch before deciding finally there.)

[Carlton Gibson <carlton.gibson@…>]

In 0670b1b4:

Fixed #30485 -- Adjusted django.utils.http.urlencode for doseq=False case.

[Mariusz Felisiak <felisiak.mariusz@…>]

In df46b329:

Refs #30485 -- Avoided unnecessary instance checks in urlencode.

Given doseq defaults to False it should avoid an unnecessary instance
check in most cases.

[Carlton Gibson <carlton.gibson@…>]

In b903bb43:

Refs #30485 -- Removed non-representative test that emitted a warning.

Previously, when running the Django test suite with warnings enabled,
the following was emitted:

/usr/lib64/python3.7/urllib/parse.py:915: BytesWarning: str() on a bytearray instance

v = quote_via(str(v), safe, encoding, errors)

This occurred due to the bytearray() being passed to
urllib.parse.urlencode() which eventually calls str() on it. The test
does not represent desired real world behavior. Rather than test for and
assert strange unspecified behavior that emits a warning, remove it.

This was also discussed in PR #11374.