markers: support new ident '|'

[hfudev]

Hi pytest team!

While I'm developing a new feature to the pytest-embedded plugin, I realize that | is not allowed in pytest markers. (Inside the pytest-embedded plugin, I'm using | as a separator.)

ERROR: Wrong expression passed to '-m': esp32|esp32p4: at column 6: unexpected character "|"

I'm wondering the reason behind this. so I'm opening this PR.

Thanks!
Hanxi

EDIT

actually use | is better than : (which is supported now)

I didn't find a way to define a marker with : inside, since everything past after the first : will be considered as a optional description.

so pytest -m "a:b" will try to search a marker called a:b, but if I put

[pytest]
  a:b: test

only marker a will be added

if we support |, we could define with

[pytest]
  a|b: test

(tested with --strict-marker)

[hfudev]

The test cases are failing, I'll fix them once the idea got approved by you.

[RonnyPfannschmidt]

It's unclear to me what exactly this solves

Marker names currently are limited to identifiers

The pipe is commonly used as logic operator in python and im under the impression that using those like that can be costly later