Correctly handle positional only arguments

[tristanlatr]

Describe the bug
Currently, docspec_python does not create correct Argument objects because it adds an argument like:

{
 "name": "/",
"type": "POSITIONAL"
}

and does not use the arguement kind Argument.Type.PositionalOnly.

To Reproduce

@pytest.mark.skipif(sys.version_info < (3, 8), reason="requires python3.8 or higher")
@docspec_test()
def test_funcdef_7_posonly_args():
  """
  def func1(x, y=3, /, z=5, w=7): pass
  def func2(x, /, *v, a=1, b=2): pass
  def func3(x, /, *, a=1, b=2, **kwargs): pass
  """

  return [
    mkfunc('func1', None, [
      Argument('x', Argument.Type.PositionalOnly),
      Argument('y', Argument.Type.PositionalOnly, default_value='3'),
      Argument('z', Argument.Type.Positional, default_value='5'),
      Argument('w', Argument.Type.Positional, default_value='7'),
    ]),
    mkfunc('func2', None, [
      Argument('x', Argument.Type.PositionalOnly),
      Argument('v', Argument.Type.PositionalRemainder),
      Argument('a', Argument.Type.KeywordOnly, default_value='1'),
      Argument('b', Argument.Type.KeywordOnly, default_value='2'),
    ]),
    mkfunc('func3', None, [
      Argument('x', Argument.Type.PositionalOnly),
      Argument('a', Argument.Type.KeywordOnly, default_value='1'),
      Argument('b', Argument.Type.KeywordOnly, default_value='2'),
      Argument('kwargs', Argument.Type.KeywordRemainder),
    ]),
  ]

Then run tests and see the diff:

E         {
E           "name": "funcdef_7_posonly_args",
E           "location": null,
E           "docstring": null,
E           "members": [
E             {
E               "name": "func1",
E               "location": null,
E               "docstring": null,
E               "modifiers": null,
E               "args": [
E                 {
E                   "name": "x",
E       -           "type": "POSITIONAL"
E       +           "type": "POSITIONAL_ONLY"
E       ?                              +++++
E                 },
E                 {
E                   "name": "y",
E       -           "type": "POSITIONAL",
E       +           "type": "POSITIONAL_ONLY",
E       ?                              +++++
E                   "default_value": "3"
E       -         },
E       -         {
E       -           "name": "/",
E       -           "type": "POSITIONAL"
E                 },
E                 {
E                   "name": "z",
E                   "type": "POSITIONAL",
E                   "default_value": "5"
E                 },
E                 {
E                   "name": "w",
E                   "type": "POSITIONAL",
E                   "default_value": "7"
E                 }
E               ],
E               "return_type": null,
E               "decorations": [],
E               "type": "function"
E             },
E             {
E               "name": "func2",
E               "location": null,
E               "docstring": null,
E               "modifiers": null,
E               "args": [
E                 {
E                   "name": "x",
E       -           "type": "POSITIONAL"
E       +           "type": "POSITIONAL_ONLY"
E       ?                              +++++
E       -         },
E       -         {
E       -           "name": "/",
E       -           "type": "POSITIONAL"
E                 },
E                 {
E                   "name": "v",
E                   "type": "POSITIONAL_REMAINDER"
E                 },
E                 {
E                   "name": "a",
E                   "type": "KEYWORD_ONLY",
E                   "default_value": "1"
E                 },
E                 {
E                   "name": "b",
E                   "type": "KEYWORD_ONLY",
E                   "default_value": "2"
E                 }
E               ],
E               "return_type": null,
E               "decorations": [],
E               "type": "function"
E             },
E             {
E               "name": "func3",
E               "location": null,
E               "docstring": null,
E               "modifiers": null,
E               "args": [
E                 {
E                   "name": "x",
E       -           "type": "POSITIONAL"
E       +           "type": "POSITIONAL_ONLY"
E       ?                              +++++
E       -         },
E       -         {
E       -           "name": "/",
E       -           "type": "POSITIONAL"
E                 },
E                 {
E                   "name": "a",
E                   "type": "KEYWORD_ONLY",
E                   "default_value": "1"
E                 },
E                 {
E                   "name": "b",
E                   "type": "KEYWORD_ONLY",
E                   "default_value": "2"
E                 },
E                 {
E                   "name": "kwargs",
E                   "type": "KEYWORD_REMAINDER"
E                 }
E               ],
E               "return_type": null,
E               "decorations": [],
E               "type": "function"
E             }
E           ]
E         }

Expected behavior
The expected behaviour would be to produce Argument with kind POSITIONAL_ONLY and do not have the extra / argument in the list.

[NiklasRosenstein]

Hey @tristanlatr , thank you for reporting this and even providing a test case. Integrating the test case now and looking into a fix.