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# cmd2.argparse_completer

## `` cmd2.argparse_completer

Module defines the ArgparseCompleter class which provides argparse-based completion to cmd2 apps.

See the header of argparse_utils.py for instructions on how to use these features.

### `` ARG_TOKENS `module-attribute`

    ARG_TOKENS = 'arg_tokens'

### `` DEFAULT_ARGPARSE_COMPLETER `module-attribute`

    DEFAULT_ARGPARSE_COMPLETER = ArgparseCompleter

### `` ArgparseCompleter

    ArgparseCompleter(parser, cmd_app, *, parent_tokens=None)

Automatic command line completion based on argparse parameters.

Create an ArgparseCompleter.

PARAMETER | DESCRIPTION
--- | ---
`parser` | Cmd2ArgumentParser instance TYPE: `Cmd2ArgumentParser`
`cmd_app` | reference to the cmd2.Cmd instance that owns this ArgparseCompleter TYPE: `Cmd`
`parent_tokens` | optional Mapping of parent parsers' arg names to their tokens This is only used by ArgparseCompleter when recursing on subcommand parsers Defaults to None TYPE: `Mapping[str, MutableSequence[str]] | None` DEFAULT: `None`

Source code in `cmd2/argparse_completer.py`

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    def __init__(
        self,
        parser: Cmd2ArgumentParser,
        cmd_app: "Cmd",
        *,
        parent_tokens: Mapping[str, MutableSequence[str]] | None = None,
    ) -> None:
        """Create an ArgparseCompleter.

        :param parser: Cmd2ArgumentParser instance
        :param cmd_app: reference to the cmd2.Cmd instance that owns this ArgparseCompleter
        :param parent_tokens: optional Mapping of parent parsers' arg names to their tokens
                              This is only used by ArgparseCompleter when recursing on subcommand parsers
                              Defaults to None
        """
        self._parser = parser
        self._cmd_app = cmd_app

        if parent_tokens is None:
            parent_tokens = {}
        self._parent_tokens = parent_tokens

        # All flags in this command
        self._flags: list[str] = []

        # Maps flags to the argparse action object
        self._flag_to_action: dict[str, argparse.Action] = {}

        # Actions for positional arguments (by position index)
        self._positional_actions: list[argparse.Action] = []

        # This will be set if self._parser has subcommands
        self._subcommand_action: argparse._SubParsersAction[Cmd2ArgumentParser] | None = None

        # Start digging through the argparse structures.
        # _actions is the top level container of parameter definitions
        for action in self._parser._actions:
            # if the parameter is flag based, it will have option_strings
            if action.option_strings:
                # record each option flag
                for option in action.option_strings:
                    self._flags.append(option)
                    self._flag_to_action[option] = action

            # Otherwise this is a positional parameter
            else:
                self._positional_actions.append(action)
                # Check if this action defines subcommands
                if isinstance(action, argparse._SubParsersAction):
                    self._subcommand_action = action

#### `` complete

    complete(text, line, begidx, endidx, tokens, *, cmd_set=None)

Complete text using argparse metadata.

PARAMETER | DESCRIPTION
--- | ---
`text` | the string prefix we are attempting to match (all matches must begin with it) TYPE: `str`
`line` | the current input line with leading whitespace removed TYPE: `str`
`begidx` | the beginning index of the prefix text TYPE: `int`
`endidx` | the ending index of the prefix text TYPE: `int`
`tokens` | Sequence of argument tokens being passed to the parser TYPE: `Sequence[str]`
`cmd_set` | if completing a command, the CommandSet the command's function belongs to, if applicable. Defaults to None. TYPE: `CommandSet[Any] | None` DEFAULT: `None`

RETURNS | DESCRIPTION
--- | ---
`Completions` | a Completions object

RAISES | DESCRIPTION
--- | ---
`CompletionError` | for various types of completion errors

Source code in `cmd2/argparse_completer.py`

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    def complete(
        self,
        text: str,
        line: str,
        begidx: int,
        endidx: int,
        tokens: Sequence[str],
        *,
        cmd_set: CommandSet[Any] | None = None,
    ) -> Completions:
        """Complete text using argparse metadata.

        :param text: the string prefix we are attempting to match (all matches must begin with it)
        :param line: the current input line with leading whitespace removed
        :param begidx: the beginning index of the prefix text
        :param endidx: the ending index of the prefix text
        :param tokens: Sequence of argument tokens being passed to the parser
        :param cmd_set: if completing a command, the CommandSet the command's function belongs to, if applicable.
                        Defaults to None.
        :return: a Completions object
        :raises CompletionError: for various types of completion errors
        """
        if not tokens:
            return Completions()

        # Positionals args that are left to parse
        remaining_positionals = deque(self._positional_actions)

        # This gets set to True when flags will no longer be processed as argparse flags
        # That can happen when -- is used or an argument with nargs=argparse.REMAINDER is used
        skip_remaining_flags = False

        # _ArgumentState of the current positional
        pos_arg_state: _ArgumentState | None = None

        # _ArgumentState of the current flag
        flag_arg_state: _ArgumentState | None = None

        # Non-reusable flags that we've parsed
        used_flags: set[str] = set()

        # Keeps track of arguments we've seen and any tokens they consumed
        consumed_arg_values: dict[str, list[str]] = {}

        # Completed mutually exclusive groups
        completed_mutex_groups: dict[argparse._MutuallyExclusiveGroup, argparse.Action] = {}

        def consume_argument(arg_state: _ArgumentState, arg_token: str) -> None:
            """Consume token as an argument."""
            arg_state.count += 1
            consumed_arg_values.setdefault(arg_state.action.dest, []).append(arg_token)

        #############################################################################################
        # Parse all but the last token
        #############################################################################################
        for token_index, token in enumerate(tokens[:-1]):
            # If we're in a positional REMAINDER arg, force all future tokens to go to that
            if pos_arg_state is not None and pos_arg_state.is_remainder:
                consume_argument(pos_arg_state, token)
                continue

            # If we're in a flag REMAINDER arg, force all future tokens to go to that until a double dash is hit
            if flag_arg_state is not None and flag_arg_state.is_remainder:
                if token == "--":  # noqa: S105
                    flag_arg_state = None
                else:
                    consume_argument(flag_arg_state, token)
                continue

            # Handle '--' which tells argparse all remaining arguments are non-flags
            if token == "--" and not skip_remaining_flags:  # noqa: S105
                # Check if there is an unfinished flag
                if (
                    flag_arg_state is not None
                    and isinstance(flag_arg_state.min, int)
                    and flag_arg_state.count < flag_arg_state.min
                ):
                    raise _UnfinishedFlagError(flag_arg_state)

                # Otherwise end the current flag
                flag_arg_state = None
                skip_remaining_flags = True
                continue

            # Check if token is a flag
            if _looks_like_flag(token, self._parser) and not skip_remaining_flags:
                # Check if there is an unfinished flag
                if (
                    flag_arg_state is not None
                    and isinstance(flag_arg_state.min, int)
                    and flag_arg_state.count < flag_arg_state.min
                ):
                    raise _UnfinishedFlagError(flag_arg_state)

                # Reset flag arg state but not positional tracking because flags can be
                # interspersed anywhere between positionals
                flag_arg_state = None
                action = None

                # Does the token match a known flag?
                if token in self._flag_to_action:
                    action = self._flag_to_action[token]
                elif self._parser.allow_abbrev:
                    candidates_flags = [flag for flag in self._flag_to_action if flag.startswith(token)]
                    if len(candidates_flags) == 1:
                        action = self._flag_to_action[candidates_flags[0]]

                if action is not None:
                    self._update_mutex_groups(action, completed_mutex_groups, used_flags, remaining_positionals)

                    # Check if the action type allows the same flag to be provided multiple times.
                    # Reusable actions (append, count, extend) preserve their history so the
                    # completion logic knows which values have already been 'consumed'.
                    if not isinstance(
                        action,
                        (
                            argparse._AppendAction,
                            argparse._AppendConstAction,
                            argparse._CountAction,
                            argparse._ExtendAction,
                        ),
                    ):
                        # For standard 'overwrite' actions (e.g., --store), providing the flag
                        # again resets its state. We mark the flags as 'used' to potentially
                        # filter them from future completion results and clear any previously
                        # recorded values for this destination.
                        used_flags.update(action.option_strings)
                        consumed_arg_values[action.dest] = []

                    new_arg_state = _ArgumentState(action)

                    # Keep track of this flag if it can receive arguments
                    if new_arg_state.max > 0:
                        flag_arg_state = new_arg_state
                        skip_remaining_flags = flag_arg_state.is_remainder

            # Check if token is a flag's argument
            elif flag_arg_state is not None:
                consume_argument(flag_arg_state, token)

                # Check if we have finished with this flag
                if flag_arg_state.count >= flag_arg_state.max:
                    flag_arg_state = None

            # Otherwise treat token as a positional argument
            else:
                # If we aren't current tracking a positional, then get the next positional arg to handle this token
                if pos_arg_state is None and remaining_positionals:
                    action = remaining_positionals.popleft()

                    # Are we at a subcommand? If so, forward to the matching completer
                    if self._subcommand_action is not None and action == self._subcommand_action:
                        if token in self._subcommand_action.choices:
                            parent_tokens = {**self._parent_tokens, **consumed_arg_values}

                            # Include the subcommand name if its destination was set
                            if action.dest != argparse.SUPPRESS:
                                parent_tokens[action.dest] = [token]

                            parser = self._subcommand_action.choices[token]
                            completer = parser.completer_class(parser, self._cmd_app, parent_tokens=parent_tokens)
                            return completer.complete(text, line, begidx, endidx, tokens[token_index + 1 :], cmd_set=cmd_set)

                        # Invalid subcommand entered, so no way to complete remaining tokens
                        return Completions()

                    # Otherwise keep track of the argument
                    pos_arg_state = _ArgumentState(action)

                # Check if we have a positional to consume this token
                if pos_arg_state is not None:
                    self._update_mutex_groups(pos_arg_state.action, completed_mutex_groups, used_flags, remaining_positionals)
                    consume_argument(pos_arg_state, token)

                    # No more flags are allowed if this is a REMAINDER argument
                    if pos_arg_state.is_remainder:
                        skip_remaining_flags = True

                    # Check if we have finished with this positional
                    elif pos_arg_state.count >= pos_arg_state.max:
                        pos_arg_state = None

                        # Check if the next positional has nargs set to argparse.REMAINDER.
                        # At this point argparse allows no more flags to be processed.
                        if remaining_positionals and remaining_positionals[0].nargs == argparse.REMAINDER:
                            skip_remaining_flags = True

        #############################################################################################
        # We have parsed all but the last token and have enough information to complete it
        #############################################################################################
        return self._handle_last_token(
            text,
            line,
            begidx,
            endidx,
            flag_arg_state,
            pos_arg_state,
            remaining_positionals,
            consumed_arg_values,
            used_flags,
            skip_remaining_flags,
            cmd_set,
        )

#### `` complete_subcommand_help

    complete_subcommand_help(text, line, begidx, endidx, tokens)

Supports cmd2's help command in the completion of subcommand names.

PARAMETER | DESCRIPTION
--- | ---
`text` | the string prefix we are attempting to match (all matches must begin with it) TYPE: `str`
`line` | the current input line with leading whitespace removed TYPE: `str`
`begidx` | the beginning index of the prefix text TYPE: `int`
`endidx` | the ending index of the prefix text TYPE: `int`
`tokens` | arguments passed to command/subcommand TYPE: `Sequence[str]`

RETURNS | DESCRIPTION
--- | ---
`Completions` | a Completions object

Source code in `cmd2/argparse_completer.py`

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    def complete_subcommand_help(self, text: str, line: str, begidx: int, endidx: int, tokens: Sequence[str]) -> Completions:
        """Supports cmd2's help command in the completion of subcommand names.

        :param text: the string prefix we are attempting to match (all matches must begin with it)
        :param line: the current input line with leading whitespace removed
        :param begidx: the beginning index of the prefix text
        :param endidx: the ending index of the prefix text
        :param tokens: arguments passed to command/subcommand
        :return: a Completions object
        """
        # If our parser has subcommands, we must examine the tokens and check if they are subcommands
        # If so, we will let the subcommand's parser handle the rest of the tokens via another ArgparseCompleter.
        if self._subcommand_action is not None:
            for token_index, token in enumerate(tokens):
                if token in self._subcommand_action.choices:
                    parser = self._subcommand_action.choices[token]
                    completer = parser.completer_class(parser, self._cmd_app)
                    return completer.complete_subcommand_help(text, line, begidx, endidx, tokens[token_index + 1 :])

                if token_index == len(tokens) - 1:
                    # Since this is the last token, we will attempt to complete it
                    return self._cmd_app.basic_complete(text, line, begidx, endidx, self._subcommand_action.choices)
                break
        return Completions()

#### `` print_help

    print_help(tokens, file=None)

Supports cmd2's help command in the printing of help text.

PARAMETER | DESCRIPTION
--- | ---
`tokens` | arguments passed to help command TYPE: `Sequence[str]`
`file` | optional file object where the argparse should write help text If not supplied, argparse will write to sys.stdout. TYPE: `IO[str] | None` DEFAULT: `None`

Source code in `cmd2/argparse_completer.py`

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    def print_help(self, tokens: Sequence[str], file: IO[str] | None = None) -> None:
        """Supports cmd2's help command in the printing of help text.

        :param tokens: arguments passed to help command
        :param file: optional file object where the argparse should write help text
                     If not supplied, argparse will write to sys.stdout.
        """
        # If our parser has subcommands, we must examine the tokens and check if they are subcommands.
        # If so, we will let the subcommand's parser handle the rest of the tokens via another ArgparseCompleter.
        if tokens and self._subcommand_action is not None:
            parser = self._subcommand_action.choices.get(tokens[0])
            if parser is not None:
                completer = parser.completer_class(parser, self._cmd_app)
                completer.print_help(tokens[1:], file)
                return
        self._parser.print_help(file)

### `` set_default_argparse_completer

    set_default_argparse_completer(completer_class)

Set the default ArgparseCompleter class for a cmd2 app.

PARAMETER | DESCRIPTION
--- | ---
`completer_class` | Type that is a subclass of ArgparseCompleter. TYPE: `type[ArgparseCompleter]`

Source code in `cmd2/argparse_completer.py`

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    def set_default_argparse_completer(completer_class: type[ArgparseCompleter]) -> None:
        """Set the default ArgparseCompleter class for a cmd2 app.

        :param completer_class: Type that is a subclass of ArgparseCompleter.
        """
        global DEFAULT_ARGPARSE_COMPLETER  # noqa: PLW0603
        DEFAULT_ARGPARSE_COMPLETER = completer_class