bug#68559: [PATCH] Improve Python shell completion

[kobarity]

Liu Hui wrote:
> On Thu, Feb 15, 2024 at 10:43 PM Mattias Engdegård
> <mattias.engdegard@gmail.com> wrote:
> >
> > The recent change on master, 0b9c7148fd, causes several failures in 
> > python-tests here (macOS). Log attached.
> >
> > It seems to have something to do with completion. Maybe the new code is 
> > sensitive to details of Python's command line editor? The standard Python 
> > interpreter is unlikely to use GNU readline, for example.
> 
> Hi,
> 
> According to the log, the problem may be related to the json library,
> which is introduced by the patch to convert the completion results
> from Python to elisp. What is the version of Python on macOS? AFAIK
> the json library is added to the Standard library since version 2.6.
> If the library is not available, could you setup a Python virtual
> environment containing the library and run the python tests in it?
> Thanks!

This is caused by the fact that the input is echoed back on MacOS
Python.  This is described in etc/PROBLEMS:

*** In Inferior Python mode, input is echoed and native completion doesn't work.

The following log shows that it tries to parse the echoed back string
as a JSON string.

Test python-completion-at-point-1 backtrace:
  json-parse-string("__PYTHON_EL_eval_file(\"/var/folders/qy/zstv16390
  python--parse-json-array("__PYTHON_EL_eval_file(\"/var/folders/qy/zs

I think the echoed back string were ignored before the patch is
applied.  However, after applying the patch, the returned string is
now parsed as JSON, which I believe is the reason for the error.

So one workaround would be to remove the echoed back string before
parsing as JSON.