Machine port close might hang

[user202729]

Sometimes Plover GUI does not respond, and it's hard to debug it.

In my particular case, I isolated the issue to this line being run while Plover is not responding

  File "plover/machine/base.py", line 219, in _error
    self._close_port()
  File "plover/machine/base.py", line 225, in _close_port
    self.serial_port.close()
  File "lib/python3.9/site-packages/serial/serialposix.py", line 451, in close
    os.close(self.fd)

which

• keeps the join() call to stop the machine thread hanging, which
• keeps the engine lock locked, which
• prevents the GUI thread from acquiring the engine lock, which
• freezes the GUI.

Suggestions...

• Perhaps Plover should have a developer-help mode to help developers figuring out which thread does not behave properly.

  (perhaps this is already done with the hanging-threads Python package, or plover-debugging-console)

• Or, in this particular case, gives a warning if some thread (most commonly the machine thread) is not responding, or other unexpected behavior happens [1].

---

I can't find any way to reproduce this reliably.

I'm not sure that this is a Plover bug because I don't know if

• it's related to one of the previous serial issues that I encountered, or

• it's caused by my workaround (see post)

• "ERROR: discarding incomplete packet: b'80'" whenever Georgi keyboard is used to wake up machine from sleep state #1208

• Serial port stopped working after suspend (sleep) and resume (wake up) #1273

Might be related issue in pyserial's repository: pyserial/pyserial#226

[1]: For example, extension plugin raises error on stop(), which prevents Plover from exiting.