Should modify() method be updated as well?
Should new argument be mentioned in the base abstract class?

After this change, we could pass more eventmask in, even wrong ones (not before since only read/write allowed). What to do with them?

@zhangyangyu

In select module, people use it by passing event mask directly.
So, I think it's necessary to check the extra_events.

Regarding to check for invalid event mask: the underlying call to epoll (or another poller API) should raise an exception for invalid mask bits.
Why check them again in selectors?

I commented on the bug tracker.

Why check them again in selectors?

@asvetlov It's the current status of register and modify, see their docs:

This returns a new SelectorKey instance, or raises a ValueError in case of invalid event mask or file descriptor, or KeyError if the file object is already registered.

And IMHO, a ValueError is easier to identify the root cause of the error than an OSError of poll. And as my test and understanding the manual, both poll and epoll_wait won't return error for invalid bitmask, it seems just pick the bitmask it thinks valid.

But it seems it's somewhat messy to implement the check. Relying on the users to always use constants in select module is also acceptable.

@Zheaoli, would you mind to resolve the conflicts and pull in main?

This PR is stale because it has been open for 30 days with no activity.