Fix arrow.get() crash when tzinfo kwarg is explicitly None

[mayuriphad]

Summary

Fixes #1259.

ArrowFactory.get() decides whether kwargs should be routed to the direct Arrow(...) constructor (the 3+ positional args path) based on whether the only kwarg present is tzinfo. It did this by checking tz is None, which cannot distinguish between "tzinfo was not passed at all" and "tzinfo=None was passed explicitly". As a result:

arrow.get('2013-01-01', 'YYYY-MM-DD', tzinfo=None)

was routed to self.type(*args, **kwargs) (the constructor path meant for calls like arrow.get(2013, 5, 5, 12, 30, 45)), which raised:

TypeError: Arrow.__init__() missing 1 required positional argument: 'day'

This is a real-world footgun for callers that pass an optional, possibly-None, timezone straight through as a kwarg (e.g. arrow.get(value, fmt, tzinfo=account.timezone) where account.timezone can be None).

Fix

Check for the key's presence rather than its value:

# tzinfo kwarg is not provided
if len(kwargs) == 1 and "tzinfo" not in kwargs:
    arg_count = 3

Now tzinfo=None behaves the same as omitting tzinfo entirely (defaults to UTC), while an explicit non-tzinfo single kwarg still correctly routes to the constructor path, and tzinfo=<value> still works as before.

Test plan

• Added test_kwarg_tzinfo_none_with_string_and_format to tests/test_factory.py, asserting arrow.get(str, fmt, tzinfo=None) produces the same result as arrow.get(str, fmt) (UTC).
• python -m pytest tests/test_factory.py -q → 49 passed, 1 skipped.
• Manually verified before the fix this raised TypeError, and after the fix arrow.get('2025-01-01', 'YYYY-MM-DD', tzinfo=None), tzinfo='US/Pacific', and omitted-tzinfo all behave correctly.
• python -m black --check arrow/factory.py tests/test_factory.py → clean.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2224255) to head (dc73690).
✅ All tests successful. No failed tests found.

Additional details and impacted files

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