fix: encode empty list/tuple as (key, '') to clear array fields

[devteamaegis]

Problem

Passing an empty list or tuple for an array field in a Stripe API update call silently does nothing — the field is omitted from the request body and the previously-set values remain unchanged.

Reproduction:

stripe.issuing.Cardholder.modify(
    "ich_...",
    spending_controls={"blocked_categories": []},
)
# blocked_categories is NOT cleared — previous values remain.

The documented workaround is to pass "" instead of []:

spending_controls={"blocked_categories": ""},  # works, but not obvious

This is because _api_encode iterates over the list with enumerate, and an empty list yields zero iterations — no key/value pair is emitted and the field disappears from the request.

Fixes #802.

Fix

Before the indexed loop in _api_encode, detect an empty list/tuple and emit (key, "") — the same encoding produced by the "" workaround — so the Stripe API receives an explicit signal to clear the field:

elif isinstance(value, list) or isinstance(value, tuple):
    if not value:
        yield (key, "")   # <-- new: clear the array
    for i, sv in enumerate(value):
        ...

Tests

Two new assertions in tests/test_encode.py:

Test	Scenario
test_encode_empty_list_yields_empty_string	[] → [("blocked_categories", "")]
test_encode_empty_tuple_yields_empty_string	() → [("tags", "")]

Both pass; existing list-encoding tests are unchanged.

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[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

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