Deprecate support of false values in urllib.parse.parse_qsl()

[serhiy-storchaka]

urllib.parse.parse_qsl() returns [] for any false value. There were no tests for this, so it was broken by accident in #115771 and restored in #116764.

Historically, the special case was needed to circumvent the fact that ''.split('&') returns [''] instead of []. parse_qsl('') and parse_qsl(b'') should return []. But zero numbers and empty sequences (like parse_qsl(0) and parse_qsl([])) should be errors. So I propose to deprecate the current behavior for general false values and make them errors in future.

There is an open question about None. There is a code in the wild that expects parse_qsl(None) to work. Although it is not difficult to add workarounds for this, it may be more convenient if None is accepted as a valid value.

Linked PRs

• gh-116897: Deprecate generic false values in urllib.parse.parse_qsl() #116903