path: root/cmd2/decorators.py

# coding=utf-8
"""Decorators for ``cmd2`` commands"""
import argparse
from typing import Any, Callable, Dict, List, Optional, Union

from . import constants
from .exceptions import Cmd2ArgparseError
from .parsing import Statement


def with_category(category: str) -> Callable:
    """A decorator to apply a category to a ``do_*`` command method.

    :param category: the name of the category in which this command should
                     be grouped when displaying the list of commands.

    :Example:

    >>> class MyApp(cmd2.Cmd):
    >>>   @cmd2.with_category('Text Functions')
    >>>   def do_echo(self, args)
    >>>     self.poutput(args)

    For an alternative approach to categorizing commands using a function, see
    :func:`~cmd2.utils.categorize`
    """
    def cat_decorator(func):
        from .utils import categorize
        categorize(func, category)
        return func
    return cat_decorator


def with_argument_list(*args: List[Callable], preserve_quotes: bool = False) -> Callable[[List], Optional[bool]]:
    """
    A decorator to alter the arguments passed to a ``do_*`` method. Default
    passes a string of whatever the user typed. With this decorator, the
    decorated method will receive a list of arguments parsed from user input.

    :param args: Single-element positional argument list containing ``do_*`` method
                 this decorator is wrapping
    :param preserve_quotes: if ``True``, then argument quotes will not be stripped
    :return: function that gets passed a list of argument strings

    :Example:

    >>> class MyApp(cmd2.Cmd):
    >>>     @cmd2.with_argument_list
    >>>     def do_echo(self, arglist):
    >>>         self.poutput(' '.join(arglist)
    """
    import functools

    def arg_decorator(func: Callable):
        @functools.wraps(func)
        def cmd_wrapper(cmd2_app, statement: Union[Statement, str], **kwargs: Dict[str, Any]) -> Optional[bool]:
            """
            Command function wrapper which translates command line into an argument list and calls actual command function

            :param cmd2_app: CLI instance passed as self parameter to command function
            :param statement: command line string or already generated Statement
            :param kwargs: any keyword arguments being passed to command function
            :return: return value of command function
            """
            _, parsed_arglist = cmd2_app.statement_parser.get_command_arg_list(command_name,
                                                                               statement,
                                                                               preserve_quotes)

            return func(cmd2_app, parsed_arglist, **kwargs)

        command_name = func.__name__[len(constants.COMMAND_FUNC_PREFIX):]
        cmd_wrapper.__doc__ = func.__doc__
        return cmd_wrapper

    if len(args) == 1 and callable(args[0]):
        # noinspection PyTypeChecker
        return arg_decorator(args[0])
    else:
        # noinspection PyTypeChecker
        return arg_decorator


# noinspection PyProtectedMember
def _set_parser_prog(parser: argparse.ArgumentParser, prog: str):
    """
    Recursively set prog attribute of a parser and all of its subparsers so that the root command
    is a command name and not sys.argv[0].
    :param parser: the parser being edited
    :param prog: value for the current parsers prog attribute
    """
    # Set the prog value for this parser
    parser.prog = prog

    # Set the prog value for the parser's subcommands
    for action in parser._actions:
        if isinstance(action, argparse._SubParsersAction):

            # Set the prog value for each subcommand
            for sub_cmd, sub_cmd_parser in action.choices.items():
                sub_cmd_prog = parser.prog + ' ' + sub_cmd
                _set_parser_prog(sub_cmd_parser, sub_cmd_prog)

            # We can break since argparse only allows 1 group of subcommands per level
            break


def with_argparser_and_unknown_args(parser: argparse.ArgumentParser, *,
                                    ns_provider: Optional[Callable[..., argparse.Namespace]] = None,
                                    preserve_quotes: bool = False) -> \
        Callable[[argparse.Namespace, List], Optional[bool]]:
    """A decorator to alter a cmd2 method to populate its ``args`` argument by parsing
    arguments with the given instance of argparse.ArgumentParser, but also returning
    unknown args as a list.

    :param parser: unique instance of ArgumentParser
    :param ns_provider: An optional function that accepts a cmd2.Cmd object as an argument
                        and returns an argparse.Namespace. This is useful if the Namespace
                        needs to be prepopulated with state data that affects parsing.
    :param preserve_quotes: if ``True``, then arguments passed to argparse maintain their quotes
    :return: function that gets passed argparse-parsed args in a ``Namespace`` and a list
             of unknown argument strings. A member called ``__statement__`` is added to the
             ``Namespace`` to provide command functions access to the :class:`cmd2.Statement`
             object. This can be useful if the command function needs to know the command line.

    :Example:

    >>> parser = argparse.ArgumentParser()
    >>> parser.add_argument('-p', '--piglatin', action='store_true', help='atinLay')
    >>> parser.add_argument('-s', '--shout', action='store_true', help='N00B EMULATION MODE')
    >>> parser.add_argument('-r', '--repeat', type=int, help='output [n] times')
    >>>
    >>> class MyApp(cmd2.Cmd):
    >>>     @cmd2.with_argparser_and_unknown_args(parser)
    >>>     def do_argprint(self, args, unknown):
    >>>         "Print the options and argument list this options command was called with."
    >>>         self.poutput('args: {!r}'.format(args))
    >>>         self.poutput('unknowns: {}'.format(unknown))
    """
    import functools

    def arg_decorator(func: Callable):
        @functools.wraps(func)
        def cmd_wrapper(cmd2_app, statement: Union[Statement, str], **kwargs: Dict[str, Any]) -> Optional[bool]:
            """
            Command function wrapper which translates command line into argparse Namespace and calls actual
            command function

            :param cmd2_app: CLI instance passed as self parameter to command function
            :param statement: command line string or already generated Statement
            :param kwargs: any keyword arguments being passed to command function
            :return: return value of command function
            :raises: Cmd2ArgparseError if argparse has error parsing command line
            """
            statement, parsed_arglist = cmd2_app.statement_parser.get_command_arg_list(command_name,
                                                                                       statement,
                                                                                       preserve_quotes)

            if ns_provider is None:
                namespace = None
            else:
                namespace = ns_provider(cmd2_app)

            try:
                args, unknown = parser.parse_known_args(parsed_arglist, namespace)
            except SystemExit:
                raise Cmd2ArgparseError
            else:
                setattr(args, '__statement__', statement)
                return func(cmd2_app, args, unknown, **kwargs)

        # argparser defaults the program name to sys.argv[0], but we want it to be the name of our command
        command_name = func.__name__[len(constants.COMMAND_FUNC_PREFIX):]
        _set_parser_prog(parser, command_name)

        # If the description has not been set, then use the method docstring if one exists
        if parser.description is None and func.__doc__:
            parser.description = func.__doc__

        # Set the command's help text as argparser.description (which can be None)
        cmd_wrapper.__doc__ = parser.description

        # Set some custom attributes for this command
        setattr(cmd_wrapper, constants.CMD_ATTR_ARGPARSER, parser)
        setattr(cmd_wrapper, constants.CMD_ATTR_PRESERVE_QUOTES, preserve_quotes)

        return cmd_wrapper

    # noinspection PyTypeChecker
    return arg_decorator


def with_argparser(parser: argparse.ArgumentParser, *,
                   ns_provider: Optional[Callable[..., argparse.Namespace]] = None,
                   preserve_quotes: bool = False) -> Callable[[argparse.Namespace], Optional[bool]]:
    """A decorator to alter a cmd2 method to populate its ``args`` argument by parsing arguments
    with the given instance of argparse.ArgumentParser.

    :param parser: unique instance of ArgumentParser
    :param ns_provider: An optional function that accepts a cmd2.Cmd object as an argument and returns an
                        argparse.Namespace. This is useful if the Namespace needs to be prepopulated with
                        state data that affects parsing.
    :param preserve_quotes: if True, then arguments passed to argparse maintain their quotes
    :return: function that gets passed the argparse-parsed args in a Namespace
             A member called __statement__ is added to the Namespace to provide command functions access to the
             Statement object. This can be useful if the command function needs to know the command line.

    :Example:

    >>> parser = argparse.ArgumentParser()
    >>> parser.add_argument('-p', '--piglatin', action='store_true', help='atinLay')
    >>> parser.add_argument('-s', '--shout', action='store_true', help='N00B EMULATION MODE')
    >>> parser.add_argument('-r', '--repeat', type=int, help='output [n] times')
    >>> parser.add_argument('words', nargs='+', help='words to print')
    >>>
    >>> class MyApp(cmd2.Cmd):
    >>>     @cmd2.with_argparser(parser, preserve_quotes=True)
    >>>     def do_argprint(self, args):
    >>>         "Print the options and argument list this options command was called with."
    >>>         self.poutput('args: {!r}'.format(args))
    """
    import functools

    def arg_decorator(func: Callable):
        @functools.wraps(func)
        def cmd_wrapper(cmd2_app, statement: Union[Statement, str], **kwargs: Dict[str, Any]) -> Optional[bool]:
            """
            Command function wrapper which translates command line into argparse Namespace and calls actual
            command function

            :param cmd2_app: CLI instance passed as self parameter to command function
            :param statement: command line string or already generated Statement
            :param kwargs: any keyword arguments being passed to command function
            :return: return value of command function
            :raises: Cmd2ArgparseError if argparse has error parsing command line
            """
            statement, parsed_arglist = cmd2_app.statement_parser.get_command_arg_list(command_name,
                                                                                       statement,
                                                                                       preserve_quotes)

            if ns_provider is None:
                namespace = None
            else:
                namespace = ns_provider(cmd2_app)

            try:
                args = parser.parse_args(parsed_arglist, namespace)
            except SystemExit:
                raise Cmd2ArgparseError
            else:
                setattr(args, '__statement__', statement)
                return func(cmd2_app, args, **kwargs)

        # argparser defaults the program name to sys.argv[0], but we want it to be the name of our command
        command_name = func.__name__[len(constants.COMMAND_FUNC_PREFIX):]
        _set_parser_prog(parser, command_name)

        # If the description has not been set, then use the method docstring if one exists
        if parser.description is None and func.__doc__:
            parser.description = func.__doc__

        # Set the command's help text as argparser.description (which can be None)
        cmd_wrapper.__doc__ = parser.description

        # Set some custom attributes for this command
        setattr(cmd_wrapper, constants.CMD_ATTR_ARGPARSER, parser)
        setattr(cmd_wrapper, constants.CMD_ATTR_PRESERVE_QUOTES, preserve_quotes)

        return cmd_wrapper

    # noinspection PyTypeChecker
    return arg_decorator