GH-145378: Use PyREPL as the default input console for pdb

[gaogaotiantian]

• Issue: Use pyrepl as the default input console for pdb #145378

[gaogaotiantian]

@pablogsal and @ambv as the original author for the new interactive shell. Could you take a look when you have some time, thanks!

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #32477993 | 📁 Comparing b04b192 against main (d71e3bc)

  🔍 Preview build  

4 files changed

± contents.html
± download.html
± whatsnew/3.15.html
± whatsnew/changelog.html

[corona10]

Suggested change

	if begidx>0:
	if begidx > 0:

[corona10]

This is not redundant declaration from L2486?

[corona10]

Nit: Please declare as common variables

banner = "*pdb interact start*"
exitmsg = "*exit from pdb interact command*"

[corona10]

def do_interact(self, arg):
    """..."""
    ns = {**self.curframe.f_globals, **self.curframe.f_locals}
    console = _PdbInteractiveConsole(ns, message=self.message)
    banner = "*pdb interact start*"
    exitmsg = "*exit from pdb interact command*"
    if self.pyrepl_input is not None:
        console.run_interact(banner, exitmsg, use_pyrepl=True)
    else:
        with self._enable_rlcompleter(ns):
            console.run_interact(banner, exitmsg, use_pyrepl=False)

[corona10]

Suggested change

	if not os.getenv("PYTHON_BASIC_REPL"):
	from _pyrepl.main import CAN_USE_PYREPL
	return CAN_USE_PYREPL
	return False
	if os.getenv('PYTHON_BASIC_REPL'):
	CAN_USE_PYREPL = False
	else:
	try:
	from _pyrepl.main import CAN_USE_PYREPL
	except ModuleNotFoundError:
	CAN_USE_PYREPL = False
	return CAN_USE_PYREPL

[corona10]

So this should be something like this:

class _PdbInteractiveConsole(code.InteractiveConsole):
    def __init__(self, ns=None, message=None):
        self._message = message
        super().__init__(locals=ns, local_exit=True)

    def write(self, data):
        if self._message is not None:
            self._message(data, end='')
        else:
            super().write(data)

    def _more_lines(self, text):
        # Generic Python multi-line completeness heuristic.
        # Strips pyrepl's trailing auto-indent before compiling.
        src = text.rstrip(" \t")
        n = len(src)
        if n > 0 and text[n-1] == '\n':
            text = src
        try:
            code_obj = self.compile(text, "<stdin>", "single")
        except (OverflowError, SyntaxError, ValueError):
            lines = text.splitlines(keepends=True)
            if len(lines) == 1:
                return False
            last = lines[-1]
            return ((last.startswith((" ", "\t")) or last.strip() != "")
                    and not last.endswith("\n"))
        return code_obj is None

[corona10]

Suggested change

	self.console = code.InteractiveConsole()
	self.console = _PdbInteractiveConsole()

[corona10]

Left some comments to avoid making this fragile against future _pyrepl changes.
Let’s depend only on APIs that asyncio already uses.

[bedevere-app]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[gaogaotiantian]

@corona10 I addressed most of the comments. There are a few things left to discuss:

1. for do_interact, we have to use run_multiline_interactive_console anyway. If you want a clearer entry I can put this logic into _PdbInteractiveConsole but we won't be able to get rid of the dependency of _pyrepl.
2. I added the history for pdb. I think one of the pain point users have is that pdb lost all the history when it restarts. For now pdb shares the same history file with python interpreter - I don't think that's a big deal right? It kind of makes sense. We can of course use a separate file, but the existing file is controlled by PYTHON_HISTORY env var and we support it natively if we just use the same history file.

[corona10]

for do_interact, we have to use run_multiline_interactive_console anyway. If you want a clearer entry I can put this logic into _PdbInteractiveConsole but we won't be able to get rid of the dependency of _pyrepl.

I think that it would be fine. asyncio already depends on it.

cpython/Lib/asyncio/__main__.py

Line 125 in 1695221

run_multiline_interactive_console,

I added the history for pdb.

Could we separate the PR for this? I think that it would be another feature.
I would like to see just pdb using pyrepl feature before the beta branch cut off, but this new feature would make another noise.

[gaogaotiantian]

Could we separate the PR for this? I think that it would be another feature.

Yeah sure. I was kind of hoping this could make it way it because that's one of the reasons that I wanted to use pyrepl for pdb - the inherited history. However, if you think it's a bit risky to onboard both, we can do only pyrepl for 3.15.

[corona10]

lgtm!

Let's fix upcoming bug during the beta period
Thanks you @gaogaotiantian