[Python] ConvertToSequenceAndInferSize leaks a reference to a list and the items when iterator raises an Exception #50591

def test_failing_iterator_does_not_leak():
    # ConvertToSequenceAndInferSize builds an intermediate list.  If the
    # iterator raises, that list and everything already stored in it leaks.
    import gc

    # Create an arbitrary long int that is probably not cached by the interpreter
    value = 10**20

    def raising_iter():
        for _ in range(5):
            yield value
        raise ValueError("boom")

    gc.collect()
    original_refcount = sys.getrefcount(value)

    with pytest.raises(ValueError, match="boom"):
        pa.array(raising_iter(), size=100)

    gc.collect()
    assert sys.getrefcount(value) == original_refcount