Using PyCSH to create an APM extension for CSH

Example APM for CSH made using PyCSH

""" Python APM test """

from __future__ import annotations

# Import pycsh, which will be linked to CSH when imported as an APM
import pycsh


def inform(name: str) -> None:
    """ This is the function that our slash command will execute,
        notice that it accepts the argument <name> """

    print(f"Hej {name}, nu kan du lave APMer i Python :)")


# Calls to pycsh.PythonSlashCommand() create new slash commands.
# Here we create a command called "inform" that runs the function inform().
# Optionally an 'argument' string may be specified, which is what "help" in CSH will show.
# When commands are instantiated on global scope,
# they will not be recreated if their module is imported/executed multiple times.
_inform = pycsh.PythonSlashCommand("inform", inform, "<name>")


def main() -> None:
    """ The "py run" command in CSH will currently execute main() by default,
        this may be changed by the "-f" argument """

    # Our slash command may also be invoked here through Python
    _inform("mig selv")

Extending an existing slash command:

_original_command = pycsh.SlashCommand(<COMMAND NAME>)

def command(*args: tuple[str]) -> None:
    """ This is Python command that extends an existing command """

    # ... Extend original command here ...

    # Extending command may of course opt out of calling the original.
    if <GUARD CLAUSE>:
        return

    # Call the original slash command, with whatever argument we received.
    _original_reboot(*args)

    # ... Perhaps do something after the original command has executed ...

_command = pycsh.PythonSlashCommand(<COMMAND NAME>, command, _original_command.args)

Here is a concrete example

_original_reboot = pycsh.SlashCommand("reboot")

def reboot(*args: tuple[str]) -> None:
    reboot_self = False
    if '-n' in args and args[args.index('-n' + 1)] == '0':
        reboot_self = True
    elif args[0] == '0':
        reboot_self = True

    
    if reboot_self:
        # Refuse to reboot node 0
        print("Refusing to reboot self")
    else:
        # Execute original (overridden) command, with whatever arguments we were given
        _original_reboot(*args)

_reboot = pycsh.PythonSlashCommand("reboot", reboot, _original_reboot.args)