TX stops after a few bytes - unless port is being read elsewhere about pyserial HOT 3 OPEN

Mmmkaay. It doesn't seem to be limited to FT232 chips or Sonoma.

I tried the script above with a Raspberry Pi and the same FT232 - worked flawlessly.
Then I downgraded a Mac to Ventura - same issue.
Then I tried an Arduino Pro Micro with USB passthrough firmware - it got more bytes through (like 60 instead of 10) but transfer was still cut short(at seemingly random lenghts) unless I had a cat -v < $serialport running in another window.

... and then I figured it out.

The connection is closed before the last bytes are actually sent - if they're in the buffer when closing I assume they're flushed and that's what's going on here.
At higher speeds I guess it's not a problem but running at 9600 baud like I do here it seems to be.

Considering this is also a problem upstream - even running echo $longstring > /dev/cu.usbserialx has this problem - I'm not sure this is a pyserial bug...

But inserting a 100ms delay before closing seems to be enough of a workaround in my case - dunno if there's a good way to make sure TX buffer is empty before closing on macOS that can or should be implemented.

from pyserial.

Check whether OS autosuspends USB.

from pyserial.

Check whether OS autosuspends USB.

Does not.
The thought did make me consider if the macOS console spits out anything useful, but doesn't seem to be the case.
I might try to downgrade a Mac to see if something went sideways with Sonoma. Already tried FTDI VCP drivers to no avail.
Validating script and dongle on a linux box tomorrow.

from pyserial.