Kernel crashes repetedly if $PS1 does not end in $

[kdelee]

I was using a powerline like shell prompt and tried using the bash kernel. It repeatedly crashed, showing a traceback in the logs that led me to believe you were looking for a prompt that ended in "$"

Traceback (most recent call last):
  File "/home/user/env/lib64/python3.5/site-packages/pexpect/expect.py", line 98, in expect_loop
    incoming = spawn.read_nonblocking(spawn.maxread, timeout)
  File "/home/user/env/lib64/python3.5/site-packages/pexpect/pty_spawn.py", line 466, in read_nonblocking
    raise TIMEOUT('Timeout exceeded.')
pexpect.exceptions.TIMEOUT: Timeout exceeded.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib64/python3.5/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib64/python3.5/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/elijah/envs/chkt/lib64/python3.5/site-packages/bash_kernel/__main__.py", line 3, in <module>
    IPKernelApp.launch_instance(kernel_class=BashKernel)
  File "/home/user/env/lib64/python3.5/site-packages/traitlets/config/application.py", line 657, in launch_instance
    app.initialize(argv)
  File "<decorator-gen-123>", line 2, in initialize
  File "/home/user/env/lib64/python3.5/site-packages/traitlets/config/application.py", line 87, in catch_config_error
    return method(app, *args, **kwargs)
  File "/home/user/env/lib64/python3.5/site-packages/ipykernel/kernelapp.py", line 457, in initialize
    self.init_kernel()
  File "/home/user/env/lib64/python3.5/site-packages/ipykernel/kernelapp.py", line 368, in init_kernel
    user_ns=self.user_ns,
  File "/home/user/env/lib64/python3.5/site-packages/traitlets/config/configurable.py", line 412, in instance
    inst = cls(*args, **kwargs)
  File "/home/user/envlib64/python3.5/site-packages/bash_kernel/kernel.py", line 81, in __init__
    self._start_bash()
  File "/home/user/env/lib64/python3.5/site-packages/bash_kernel/kernel.py", line 104, in _start_bash
    line_output_callback=self.process_output)
  File "/home/user/envlib64/python3.5/site-packages/bash_kernel/kernel.py", line 33, in __init__
    prompt_change, extra_init_cmd=extra_init_cmd)
  File "/home/user/env/lib64/python3.5/site-packages/pexpect/replwrap.py", line 51, in __init__
    prompt_change.format(new_prompt, continuation_prompt))
  File "/home/elijah/envs/chkt/lib64/python3.5/site-packages/pexpect/replwrap.py", line 61, in set_prompt
    self.child.expect(orig_prompt)
  File "/home/user/env/lib64/python3.5/site-packages/pexpect/spawnbase.py", line 327, in expect
    timeout, searchwindowsize, async_)
  File "/home/user/env/lib64/python3.5/site-packages/pexpect/spawnbase.py", line 355, in expect_list
    return exp.expect_loop(timeout)
  File "/home/user/env/lib64/python3.5/site-packages/pexpect/expect.py", line 106, in expect_loop
    return self.timeout(e)
  File "/home/user/envlib64/python3.5/site-packages/pexpect/expect.py", line 70, in timeout
    raise TIMEOUT(msg)
pexpect.exceptions.TIMEOUT: Timeout exceeded.
<pexpect.pty_spawn.spawn object at 0x7ff254664240>
command: /usr/bin/bash
args: [b'/usr/bin/bash', b'--rcfile', b'/home/user/env/lib64/python3.5/site-packages/pexpect/bashrc.sh']
buffer (last 100 chars): '5;250;48;5;240msfw\xa0\x1b[0;38;5;245;48;5;240;22m\ue0b1\xa0\x1b[0;38;5;252;48;5;240;1mchkt\xa0\x1b[0;38;5;240;49;22m\ue0b0\xa0\x1b[0m'
before (last 100 chars): '5;250;48;5;240msfw\xa0\x1b[0;38;5;245;48;5;240;22m\ue0b1\xa0\x1b[0;38;5;252;48;5;240;1mchkt\xa0\x1b[0;38;5;240;49;22m\ue0b0\xa0\x1b[0m'
after: <class 'pexpect.exceptions.TIMEOUT'>
match: None
match_index: None
exitstatus: None
flag_eof: False
pid: 28695
child_fd: 46
closed: False
timeout: 30
delimiter: <class 'pexpect.exceptions.EOF'>
logfile: None
logfile_read: None
logfile_send: None
maxread: 2000
ignorecase: False
searchwindowsize: None
delaybeforesend: 0.05
delayafterclose: 0.1
delayafterterminate: 0.1
searcher: searcher_re:
    0: re.compile("\$")

It started working once I disabled my powerline by commenting out the part of my .bashrc that makes me use thep powerline and putting a more "traditional" PS1 prompt in there. i.e. export PS1="$USER@$HOSTNAME:${PWD} \$ "

Ideally, I'd like not to have to do this to use this plugin, which I really like the idea of!

I took a quick look and it was not immediately obvious how this regex is getting formed because it is not verbatim in the code. If you have tips on how it gets made, I would make a PR to fix this.

[takluyver]

It's supposed to override your PS1 by starting bash with this script. It might be missing something, though. I'm just working on fixing an issue where PROMPT_COMMAND overrides it - https://github.com/pexpect/pexpect/pull/459