bug#71440: Python Inferior Mode Can’t Recognize My Prompt

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 12 Jun 2024 01:24:39 +0900
> From: kobarity <kobarity@gmail.com>
> Cc: 71440@debbugs.gnu.org
> 
> 
> > Eli Zaretskii wrote:
> > > > > I wonder how PS1 and PS2 are at all relevant when using 
> > > > > python-shell-send-buffer?  That function sends the buffer
> > > > > text to Python, so where do PS1 and PS2 come into play,
> > > > > and why does Python say "__PYTHON_EL_eval is not defined" 
> > > > > just because you have PS1 and PS2 customized?
> 
> PS1 and PS2 are set to `comint-prompt-regexp', and used to identify
> execution completion.  The prompts must also be identified to
> determine if the command can be sent.
> 
> Python REPL cannot accept the Python code as is.  For example, try
> pasting the following code to the REPL:
> 
> if True:
>     print("True")
> print("Hi")
> 
> You should see the message "SyntaxError: invalid syntax".  This is
> because the REPL requires an empty line to recognize the completion of
> a block.  For such reasons, `python-shell-send-*' sends a string as
> the argument to __PYTHON_EL_eval instead of sending the code as is.
> 
> __PYTHON_EL_eval is defined during the initialization of inferior
> Python, but if the prompt is not recognized, its definition cannot be
> done either.
> 
> The prompts are recognized by `python-shell-prompt-detect'.  A small
> Python code sends PS1, etc. to Emacs as an array of JSON strings.
> However, the JSON strings are hand-crafted for compatibility, as noted
> in the comments below.
> 
>                     ;; JSON is built manually for compatibility
> 
> The json package was added in Python 2.6, so I assume it is to support
> Python 2.5 and earlier.  This is fine for prompts consisting only of
> ordinary characters, but will not result in a correct JSON string if
> it contains escape sequences.
> 
> The attached improved patch uses the json package if available, so it
> can handle escape sequences; without the json package, it works as
> before.  It means that prompts containing escape sequences can be
> recognized in Python 2.6 or later.  I have also added an ERT to check
> this.

Thanks, but what do you mean by "json package" here?  Emacs nowadays
has JSON capabilities built in, so no optional features should be
required.  I did I misunderstand what you say above?