In some cases `PromptSession.promt()` returns None

I am reporting a very elusive and hard-to-reproduce issue.

While using ipdb.set_trace() inside https://github.com/isaac-sim/IsaacLab (with docker), I discovered that the debugger hard breaks if used inside the simulation loop (e.g. simulation app is launched and running). Regular pdb does not have such issues.

After some tracing, I figured that parsing of promts by Ipython/terminal/debugger.py somehow returns None here. This line essentially relies on PromptSession.promt() of python-prompt-toolkit, here.

After downgrading to prompt-toolkit==3.0.36 the issue went away.

So,

this combination of ipython with promt_toolkit does not work

ipython==8.26.0
prompt_toolkit==3.0.47

but this one does

ipython==8.26.0
prompt-toolkit==3.0.36

I am fully aware that this an awful bug report, as it is not reproducible without running some 3rd party tools in a docker. But at least it's some documentation of the issue.

Start by comparing prompt-toolkit 3.0.36 and 3.0.47 with IPython 8.26.0, focusing on PromptSession.prompt() in src/prompt_toolkit/shortcuts/prompt.py and the caller in IPython/terminal/debugger.py. Reproduce the None result in the IsaacLab Docker simulation-loop context if possible, then identify the version-related behavior and verify the fix against that scenario.