Support coverage plugins with sys.monitoring

[scoder]

Is your feature request related to a problem? Please describe.

Running coverage.py on Cython code with sys.monitoring in Py3.13 disables the Cython coverage plugin:

coveragepy/coverage/control.py

Lines 565 to 568 in 7f33622

	# Early warning if we aren't going to be able to support plugins.
	if self._plugins.file_tracers and not self._collector.supports_plugins:
	self._warn(
	"Plugin file tracers ({}) aren't supported with {}".format(

Describe the solution you'd like
Plugins should work the same with the old tracing and new monitoring infrastructure.

Additional context
I'm currently working on getting Cython to use the monitoring C-API, but found that coverage.py doesn't support both together as it stands.

[scoder]

Ping @nedbat. Any hint on what's missing to make this work?

[nedbat]

Hi, sorry to let this sit. What plugin behavior in particular are you looking for? The key idea of sys.monitoring that makes it fast is to disable an event once it's fired, but some plugin methods would need the events to be re-enabled. This is extra choreography that I haven't really thought through yet, and I hope it doesn't completely nullify the speed benefits.

[scoder]

Our coverage plugin is here:
https://github.com/cython/cython/blob/master/Cython/Coverage.py

We don't need access to events, we just do file lookups and line matching.