io/wait: wait_readable/writable working different than IO.select when descriptor not open
Coming from this pending issue:
Gist of it:
f = IO.popen("/bin/sh","r+")
f.wait_writable #=> IOError: not opened for writing
IO.select(nil,[f],nil,10) #=> no error
The way I see it, it should have the same behaviour, i.e. either IO.select should complain, or wait_writable should just return nil.
Updated by jeremyevans0 (Jeremy Evans) about 2 months ago
I don't think this is a bug. It makes sense for
IO#wait_writable to raise an exception, because the specific
IO instance will never be writable after
close_write. As the documentation for
IO.select indicates, it calls
select(2), and returns arrays showing which
IO objects you can take action on. I don't think that it would make sense for
IO.select to go through all input or output read and write arrays and check if the file descriptors are still open for the appropriate direction. Even if it could, raising in that case would not be helpful, as you would lose information on which other file descriptors you could take action on.
One thing that may be helpful would be the addition of
IO#write_closed?, as currently I'm not sure how you can determine if an
IO instance is closed in a given direction. However, that would be a feature request, not a bug fix.