Argument Clinic: a lone optional group generates METH_O

[serhiy-storchaka]

Bug report

If the only parameter of a function is in an optional group, Argument Clinic generates METH_O:

/*[clinic input]
m.f
    [
    a: object
    ]
    /
[clinic start generated code]*/

#define M_F_METHODDEF    \
    {"f", (PyCFunction)m_f, METH_O, m_f__doc__},

static PyObject *
m_f(PyObject *module, int group_right_1, PyObject *a)

The group is ignored: the argument becomes mandatory, and group_right_1 is never computed nor passed.

Linked PRs

• gh-155266: Fix Argument Clinic for a lone optional group #155267