WIP hack around mark object [skip ci]

[nicoddemus]

Hey @RonnyPfannschmidt,

The topic of mark objects came up at work again, and I decided to be a bit of hacking to see how far I could get based on the discussion in #5424.

I basically removed some checks and made MarkDecorator callable, so this is possible:

import attr

import pytest


@attr.s
class MyMark:
    name = attr.ib(type=str)
    x = attr.ib(type=int)


@pytest.mark(MyMark('mymark', 10))
def test(request):
    m = request.node.get_closest_marker(name='mymark')
    assert isinstance(MyMark)
    assert m.x == 10

No registration necessary, just a plain object with the only restriction that it needs to have a name: str attribute (which can also be lifted easily).

Wanted to share because I'm excited that this was possible with so little work (thanks to all the previous work you've done here of course).

[RonnyPfannschmidt]

lovely start, i believe we mainly need tests and a good setup for the unpacking/repacking

we might want to add a keyword only parameter called instance_of for the iteration functions

[RonnyPfannschmidt]

for safety, this should only extract markdecorators

[nicoddemus]

Note: combination should be diallowed, so this:

pytest.mark(obj)(1)

Should raise a `TypeError.

[nicoddemus]

Closing for now as this was mostly an experiment. I have no plans to continue working on this on the near term, but of course others are free to use this as basis to implement the whole thing! 👍