cmd.Cmd completion fails in some cases, must allow the definition of readline completion delimiters

[diegorubert]

Bug report

Bug description:

cmd.Cmd does not allow the definition of readline completion delimiters, therefore, complete_*() methods will fail with completion options containing dashes (or other characters in readline's default list of delimiters).

Defining a Cmd.completer_delims (by default None) and then calling readline.set_completer_delims(self.completer_delims) (if Cmd.completer_delims is not None) after importing readline will do the trick.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[ZeroIntensity]

I was unable to reproduce this. By this report, the following should fail (it does not on Python 3.12):

import cmd


class ReproShell(cmd.Cmd):
    def do_foo(self, s):
        pass

    def complete_foo(self, *args):
        return [
            "-hello",
            "world",
        ]  # This should "fail" -- the report did not clarify if that meant an exception, or what


if __name__ == "__main__":
    ReproShell().cmdloop()  # Type "foo " and then tab

[catherinedevlin]

I think I understand (and confirmed, on 3.15.0a0) @diegorubert 's issue. Stealing the sample from https://pymotw.com/3/cmd/

import cmd

class ReproShell(cmd.Cmd):
    def do_greet(self, s):
        print(f"Greetings, {s}!")

    FRIENDS = ["chelnik", "-cheuk", "--chicago"]

    def complete_greet(self, text_passed, line, begidx, endidx):
        print(f"\n{text_passed=}\n")
        if not text_passed:
            completions = self.FRIENDS[:]
        else:
            completions = [
                f
                for f in self.FRIENDS
                if f.startswith(text_passed)
            ]
        return completions
    
if __name__ == "__main__":
    ReproShell().cmdloop()  # Type "foo " and then tab

If you type greet -c or greet --c, the text_passed to .complete_greet is stripped of leading hyphens. If you type greet -c<TAB>, you get autocompleted to "chelnik" instead of "cheuk", because .complete_greet got just "c".