bug#28580: python.el: native completion setup failed

[Noam Postavsky <npostavs@users.sourceforge.net>]

Андрей Парамонов <cmr.pent@gmail.com> writes:

> It didn't help, unfortunately: I was indeed missing pyreadline, but
> installing it from conda repo made no difference :-(
> Neither did using "-i -u" as interactive Python arg.
>
> I vaguely remember this working with older Pythons -- what could
> probably change?

Hmm, can you try running the python code from
python-shell-completion-native-setup manually from a prompt and see what
comes out? (or where it goes wrong)

def __PYTHON_EL_native_completion_setup():
    try:
        import readline

        try:
            import __builtin__
        except ImportError:
            # Python 3
            import builtins as __builtin__

        builtins = dir(__builtin__)
        is_ipython = ('__IPYTHON__' in builtins or
                      '__IPYTHON__active' in builtins)

        class __PYTHON_EL_Completer:
            '''Completer wrapper that prints candidates to stdout.

            It wraps an existing completer function and changes its behavior so
            that the user input is unchanged and real candidates are printed to
            stdout.

            Returned candidates are '0__dummy_completion__' and
            '1__dummy_completion__' in that order ('0__dummy_completion__' is
            returned repeatedly until all possible candidates are consumed).

            The real candidates are printed to stdout so that they can be
            easily retrieved through comint output redirect trickery.
            '''

            PYTHON_EL_WRAPPED = True

            def __init__(self, completer):
                self.completer = completer
                self.last_completion = None
                self.print_mode = True

            def __call__(self, text, state):
                if state == 0:
                    # Set the first dummy completion.
                    self.last_completion = None
                    completion = '0__dummy_completion__'
                else:
                    completion = self.completer(text, state - 1)

                if not completion:
                    if self.last_completion != '1__dummy_completion__':
                        # When no more completions are available, returning a
                        # dummy with non-sharing prefix allow ensuring output
                        # while preventing changes to current input.
                        # Coincidentally it's also the end of output.
                        completion = '1__dummy_completion__'
                elif completion.endswith('('):
                    # Remove parens on callables as it breaks completion on
                    # arguments (e.g. str(Ari<tab>)).
                    completion = completion[:-1]
                self.last_completion = completion

                if completion in (
                        '0__dummy_completion__', '1__dummy_completion__'):
                    return completion
                elif completion:
                    # For every non-dummy completion, return a repeated dummy
                    # one and print the real candidate so it can be retrieved
                    # by comint output filters.
                    if self.print_mode:
                        print (completion)
                        return '0__dummy_completion__'
                    else:
                        return completion
                else:
                    return completion

        completer = readline.get_completer()

        if not completer:
            # Used as last resort to avoid breaking customizations.
            import rlcompleter
            completer = readline.get_completer()

        if completer and not getattr(completer, 'PYTHON_EL_WRAPPED', False):
            # Wrap the existing completer function only once.
            new_completer = __PYTHON_EL_Completer(completer)
            if not is_ipython:
                readline.set_completer(new_completer)
            else:
                # Try both initializations to cope with all IPython versions.
                # This works fine for IPython 3.x but not for earlier:
                readline.set_completer(new_completer)
                # IPython<3 hacks readline such that `readline.set_completer`
                # won't work.  This workaround injects the new completer
                # function into the existing instance directly:
                instance = getattr(completer, 'im_self', completer.__self__)
                instance.rlcomplete = new_completer

        if readline.__doc__ and 'libedit' in readline.__doc__:
            readline.parse_and_bind('bind ^I rl_complete')
        else:
            readline.parse_and_bind('tab: complete')
            # Require just one tab to send output.
            readline.parse_and_bind('set show-all-if-ambiguous on')

        print ('python.el: native completion setup loaded')
    except:
        print ('python.el: native completion setup failed')

__PYTHON_EL_native_completion_setup()