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.

[cla-assistant]

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[cla-assistant]

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[jar-stripe]

Hi @devteamaegis , thank you for the PR! This fix seems reasonable and we are reviewing. In the mean time we need you to sign our CLA for us to be able to merge it in; can you take a look at that please?

[jar-stripe]

Unfortunately, we are unable to merge PRs from contributors that have not signed our CLA. Closing.