{Core} Make parser compatible with Python 3.11's argparse

[jiasli]

Description

Fix #23015
A rework of #24109

Azure CLI fails on Python 3.11:

> az version
...
argparse.ArgumentError: argument _command_package: conflicting subparser: version

Python 3.11 updated argparse's behavior:

https://docs.python.org/3.11/whatsnew/changelog.html#id50

bpo-39716: Raise an ArgumentError when the same subparser name is added twice to an argparse.ArgumentParser. This is consistent with the (default) behavior when the same option string is added twice to an ArgumentParser.

The PR for this change is python/cpython#18605

Per Git blame,

• subparser.choices[command_verb] = command_verb was renamed from subparser.choices[command_name] = command_name by 517872a
• subparser.choices[command_name] = command_name was introduced as early as 2a6f545

Running this line makes subparser.choices a str:str mapping.

In argparse._SubParsersAction, self.choices is the same dict object as self._name_parser_map:

https://github.com/python/cpython/blob/v3.10.8/Lib/argparse.py#L1159

class _SubParsersAction(Action):
    ...
    def __init__(self,
        ....
        super(_SubParsersAction, self).__init__(
            ...
            choices=self._name_parser_map,

https://github.com/python/cpython/blob/v3.10.8/Lib/argparse.py#L769

class Action(_AttributeHolder):
    ...
    def __init__(self,
        ...
        self.choices = choices

Later, in argparse._SubParsersAction.add_parser, self._name_parser_map's command_verb key is overwritten as a str:parser mapping:

azure-cli/src/azure-cli-core/azure/cli/core/parser.py

Line 100 in 110f7b4

command_parser = subparser.add_parser(command_verb,

https://github.com/python/cpython/blob/v3.10.8/Lib/argparse.py#L1179

    def add_parser(self, name, **kwargs):
        ...
        self._name_parser_map[name] = parser

Before running this line:

After running this line:

So subparser.choices[command_verb] = command_verb is basically a no-op, but it starts to cause failure in Python 3.11 due to the new duplication check.

I am not sure why subparser.choices[command_verb] = command_verb was introduced by 2a6f545 6 years ago, possibly due to some Python 2 argparse's limitation?

I checked http://bugs.python.org/issue9253 mentioned in the comment, but didn't see how it is related to this workaround.

We can think it in another way. Since Python 3.11's argparse has no functionality change (only an additional check), if this line should be removed for Python 3.11, it should also be removed for Python 3.10-.

[yonzhan]

Core