Sufficiently slow external PROMPT command can cause errors if coreutils is loaded

[chipbuster]

xonfig

Details

xontrib load coreutils # Comment out to fix issue

$XONSH_SHOW_TRACEBACK = True

def prompt():
    return $(sleep 0.5 | echo """Prompt>""" | cat)

$PROMPT = prompt

Expected Behavior

The shell doesn't crash.

Current Behavior

When running a sufficiently slow external command as PROMPT in xonsh, one of two things can happen:

• An error message appears of the form Failed to format prompt <something> -> <class 'TypeError'>:'NoneType' object cannot be interpreted as an integer
• The shell crashes altogether with an exception.

In the output below, I was mashing ENTER at a blank prompt, and the exception occurred after 3 attempts.

The issue completely disappears if xontrib load coreutils is commented.

Traceback (if applicable)

Details

/home/chipbuster/.config/xonsh/rc.xsh:1:8 - xontrib load coreutils # Comment out to fix issue
/home/chipbuster/.config/xonsh/rc.xsh:1:8 + ![xontrib load coreutils] # Comment out to fix issue
Prompt>

Failed to format prompt `<function prompt at 0x7fb8a5665fc0>`-> <class 'TypeError'>:'NoneType' object cannot be interpreted as an integer
Prompt>

Failed to format prompt `<function prompt at 0x7fb8a5665fc0>`-> <class 'TypeError'>:'NoneType' object cannot be interpreted as an integer
Prompt>

Failed to format prompt `<function prompt at 0x7fb8a5665fc0>`-> <class 'TypeError'>:'NoneType' object cannot be interpreted as an integer
xonsh: To log full traceback to a file set: $XONSH_TRACEBACK_LOGFILE = <filename>
Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/xonsh/prompt/__amalgam__.py", line 880, in __call__
    toks = self._format_prompt(template=template, **kwargs)
  File "/usr/lib/python3.10/site-packages/xonsh/ptk_shell/formatter.py", line 46, in _format_prompt
    toks = super()._format_prompt(
  File "/usr/lib/python3.10/site-packages/xonsh/prompt/__amalgam__.py", line 892, in _format_prompt
    tmpl = template() if callable(template) else template
  File "/home/chipbuster/.config/xonsh/rc.xsh", line 6, in prompt
    return $(sleep 0.5 | echo """Prompt>""" | cat)
  File "/usr/lib/python3.10/site-packages/xonsh/built_ins.py", line 166, in subproc_captured_stdout
    return xonsh.procs.specs.run_subproc(cmds, captured="stdout", envs=envs)
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 3582, in run_subproc
    command.end()
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 928, in end
    self._end(tee_output=tee_output)
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 936, in _end
    for _ in self.tee_stdout():
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 838, in tee_stdout
    for line in self.iterraw():
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 723, in iterraw
    task = xj.wait_for_active_job()
  File "/usr/lib/python3.10/site-packages/xonsh/__amalgam__.py", line 11043, in wait_for_active_job
    _, wcode = os.waitpid(obj.pid, os.WUNTRACED)
TypeError: 'NoneType' object cannot be interpreted as an integer

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/xonsh/prompt/__amalgam__.py", line 987, in _failover_template_format
    return template()
  File "/home/chipbuster/.config/xonsh/rc.xsh", line 6, in prompt
    return $(sleep 0.5 | echo """Prompt>""" | cat)
  File "/usr/lib/python3.10/site-packages/xonsh/built_ins.py", line 166, in subproc_captured_stdout
    return xonsh.procs.specs.run_subproc(cmds, captured="stdout", envs=envs)
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 3582, in run_subproc
    command.end()
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 928, in end
    self._end(tee_output=tee_output)
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 936, in _end
    for _ in self.tee_stdout():
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 838, in tee_stdout
    for line in self.iterraw():
  File "/usr/lib/python3.10/site-packages/xonsh/procs/__amalgam__.py", line 723, in iterraw
    task = xj.wait_for_active_job()
  File "/usr/lib/python3.10/site-packages/xonsh/__amalgam__.py", line 11043, in wait_for_active_job
    _, wcode = os.waitpid(obj.pid, os.WUNTRACED)
TypeError: 'NoneType' object cannot be interpreted as an integer
Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/xonsh/__amalgam__.py", line 21797, in main
    sys.exit(main_xonsh(args))
  File "/usr/lib/python3.10/site-packages/xonsh/__amalgam__.py", line 21835, in main_xonsh
    shell.shell.cmdloop()
  File "/usr/lib/python3.10/site-packages/xonsh/ptk_shell/shell.py", line 402, in cmdloop
    line = self.singleline(auto_suggest=auto_suggest)
  File "/usr/lib/python3.10/site-packages/xonsh/ptk_shell/shell.py", line 371, in singleline
    line = self.prompter.prompt(**prompt_args)
  File "/usr/lib/python3.10/site-packages/prompt_toolkit/shortcuts/prompt.py", line 1033, in prompt
    return self.app.run(
  File "/usr/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 937, in run
    return loop.run_until_complete(
  File "/usr/lib/python3.10/asyncio/base_events.py", line 641, in run_until_complete
    return future.result()
  File "/usr/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 856, in run_async
    return await _run_async2()
  File "/usr/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 826, in _run_async2
    result = await _run_async()
  File "/usr/lib/python3.10/site-packages/prompt_toolkit/application/application.py", line 741, in _run_async
    with self.input.raw_mode(), self.input.attach(
  File "/usr/lib/python3.10/site-packages/prompt_toolkit/input/vt100.py", line 266, in __enter__
    termios.tcsetattr(self.fileno, termios.TCSANOW, newattr)
termios.error: (5, 'Input/output error')
Xonsh encountered an issue during launch
Failback to /bin/sh
sh: initialize_job_control: no job control in background: Bad file descriptor
sh-5.1$

Steps to Reproduce

I believe that simply using the config above, launching xonsh, and mashing ENTER at a blank prompt should trigger the bug. However, both systems tested with this bug seem to be using Python 3.10. I attempted to test this with Python 3.8 and I think I got a reproduction, but I'm not 100% certain I did it correctly (I'm not terribly familiar with python environments), so let me know if this fails to reproduce.

For community

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[gforsyth]

Hey @chipbuster -- thanks for reporting! I have to dig in a bit more, but the root cause of this is that the coreutils implementation of cat is doing something a bit fishy with our process runner.

There are two workarounds:

1. Don't load coreutils (especially since it seems like you're on linux or OSX and should have those utils available already)
2. Specifically, don't use cat if you do load coreutils -- that is, ignore the cat alias that gets created by coreutils and directly call the cat binary, e.g. in your example:

def prompt():
    return $(sleep 0.5 | echo  """Prompt>""" | /usr/bin/cat)

[TeddyHuang-00]

1. Don't load coreutils

I tried this workaround and it works well on all of my *nix machine, including native Debian, Debian on WSL2 and OSX. Thanks a lot for that! 😄

[eugenesvk]

Had a similar issue trying to pin down why execx($(starship init xonsh)) would crash the shell on OSX!

Another issue I had was that the fallback /bin/bash process would take a lot of CPU% even after I close the terminal. Any idea how to remove this fallback behavior?

As a workaround, this seems to work (add it after loading coreutils)

del aliases['cat'] # workaround for this bug https://github.com/xonsh/xontrib-coreutils/issues/1