Python `bytearray` not accepted for Cython `bytes` argument

This seems like a mistake, as Python’s bytearray is a strict superset of Python’s bytes — so when accepting a bytes argument, I can’t think of a good reason not to accept a bytearray object, but right now this fails:

# iscsi.pyx

cdef class Task:
    cdef scsi_task *_task

    def __init__(self, bytes cdb, scsi_xfer_dir direction, size_t xferlen):
        self._task = scsi_create_task(len(cdb), cdb, direction, xferlen)

    @property
    def status(self):
        return scsi_task_get_status(self._task, NULL)

# iscsi_test.py
class TaskTest(unittest.TestCase):
    def test_bytearray(self):
        task = iscsi.Task(
            bytearray(b"\x12\x00\x00\x00\x60\x00"), iscsi.SCSI_XFER_READ, 96
        )
        self.assertIsNotNone(task)

Output:

self = <tests.iscsi_test.TaskTest testMethod=test_bytearray>

    def test_bytearray(self):
>       task = iscsi.Task(
            bytearray(b"\x12\x00\x00\x00\x60\x00"), iscsi.SCSI_XFER_READ, 96
        )
E       TypeError: Argument 'cdb' has incorrect type (expected bytes, got bytearray)

tests/iscsi_test.py:28: TypeError

[da-woods]

It looks like there’s already something to this effect in the documentation:

https://cython.readthedocs.io/en/latest/src/tutorial/strings.html#accepting-strings-from-python-code

In the case that the API only deals with byte strings, i.e. binary data or encoded text, it is best not to type the input argument as something like bytes, because that would restrict the allowed input to exactly that type and exclude both subtypes and other kinds of byte containers, e.g. bytearray objects or memory views.

The challenge is always to find the place in the documentation where the information will be seen might the right people who need to see it. I’m sure improvements to the documentation are welcome (although I won’t be the one deciding if they’re accepted)

[scoder]

I’ll close this ticket since it works as designed. Feel free to send a PR for the docs.