python/mach/mach/dispatcher.py
author Mike Hommey <mh+mozilla@glandium.org>
Tue, 07 Oct 2014 07:36:27 +0900
changeset 232299 4e8f29e386bda1cb17ffb0e02e62cf6ece3cc000
parent 223571 041030a16baefe2127c4b4d672a2942816b35a0d
child 232719 c547a8d0f0768da36ecaa73bcf0e4fb71f65fe14
permissions -rw-r--r--
Bug 1076649 - Remove the '+' prefixing from mach commands with allow_all_arguments=True. r=gps The reason to use '+' prefixing was to distinguish between options to the mach command itself, and options that are passed down to whatever the command does (like mach run passing down args to the built application). That makes things unnecessarily awkward, and quite non-standard. Instead, use standard '-' prefixing, and pass all the unknown arguments down. If there is overlap between the known arguments and arguments supported by the underlying tool (like -remote when using mach run), it is possible to use '--' to mark all following arguments as being targetted at the underlying tool. For instance: mach run -- -remote something would run firefox -remote something while mach run -remote something would run firefox something As allow_all_arguments is redundant with the presence of a argparse.REMAINDER CommandArgument, allow_all_arguments is removed. The only mach command with a argparse.REMAINDER CommandArgument without allow_all_arguments was "mach dmd", and it did so because it didn't want to use '+' prefixes.

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

from __future__ import unicode_literals

import argparse
import difflib
import sys

from operator import itemgetter

from .base import (
    NoCommandError,
    UnknownCommandError,
    UnrecognizedArgumentError,
)


class CommandFormatter(argparse.HelpFormatter):
    """Custom formatter to format just a subcommand."""

    def add_usage(self, *args):
        pass


class CommandAction(argparse.Action):
    """An argparse action that handles mach commands.

    This class is essentially a reimplementation of argparse's sub-parsers
    feature. We first tried to use sub-parsers. However, they were missing
    features like grouping of commands (http://bugs.python.org/issue14037).

    The way this works involves light magic and a partial understanding of how
    argparse works.

    Arguments registered with an argparse.ArgumentParser have an action
    associated with them. An action is essentially a class that when called
    does something with the encountered argument(s). This class is one of those
    action classes.

    An instance of this class is created doing something like:

        parser.add_argument('command', action=CommandAction, registrar=r)

    Note that a mach.registrar.Registrar instance is passed in. The Registrar
    holds information on all the mach commands that have been registered.

    When this argument is registered with the ArgumentParser, an instance of
    this class is instantiated. One of the subtle but important things it does
    is tell the argument parser that it's interested in *all* of the remaining
    program arguments. So, when the ArgumentParser calls this action, we will
    receive the command name plus all of its arguments.

    For more, read the docs in __call__.
    """
    def __init__(self, option_strings, dest, required=True, default=None,
        registrar=None, context=None):
        # A proper API would have **kwargs here. However, since we are a little
        # hacky, we intentionally omit it as a way of detecting potentially
        # breaking changes with argparse's implementation.
        #
        # In a similar vein, default is passed in but is not needed, so we drop
        # it.
        argparse.Action.__init__(self, option_strings, dest, required=required,
            help=argparse.SUPPRESS, nargs=argparse.REMAINDER)

        self._mach_registrar = registrar
        self._context = context

    def __call__(self, parser, namespace, values, option_string=None):
        """This is called when the ArgumentParser has reached our arguments.

        Since we always register ourselves with nargs=argparse.REMAINDER,
        values should be a list of remaining arguments to parse. The first
        argument should be the name of the command to invoke and all remaining
        arguments are arguments for that command.

        The gist of the flow is that we look at the command being invoked. If
        it's *help*, we handle that specially (because argparse's default help
        handler isn't satisfactory). Else, we create a new, independent
        ArgumentParser instance for just the invoked command (based on the
        information contained in the command registrar) and feed the arguments
        into that parser. We then merge the results with the main
        ArgumentParser.
        """
        if namespace.help:
            # -h or --help is in the global arguments.
            self._handle_main_help(parser, namespace.verbose)
            sys.exit(0)
        elif values:
            command = values[0].lower()
            args = values[1:]

            if command == 'help':
                if args and args[0] not in ['-h', '--help']:
                    # Make sure args[0] is indeed a command.
                    self._handle_subcommand_help(parser, args[0])
                else:
                    self._handle_main_help(parser, namespace.verbose)
                sys.exit(0)
            elif '-h' in args or '--help' in args:
                # -h or --help is in the command arguments.
                self._handle_subcommand_help(parser, command)
                sys.exit(0)
        else:
            raise NoCommandError()

        # Command suggestion
        if command not in self._mach_registrar.command_handlers:
            # We first try to look for a valid command that is very similar to the given command.
            suggested_commands = difflib.get_close_matches(command, self._mach_registrar.command_handlers.keys(), cutoff=0.8)
            # If we find more than one matching command, or no command at all, we give command suggestions instead
            # (with a lower matching threshold). All commands that start with the given command (for instance: 'mochitest-plain',
            # 'mochitest-chrome', etc. for 'mochitest-') are also included.
            if len(suggested_commands) != 1:
                suggested_commands = set(difflib.get_close_matches(command, self._mach_registrar.command_handlers.keys(), cutoff=0.5))
                suggested_commands |= {cmd for cmd in self._mach_registrar.command_handlers if cmd.startswith(command)}
                raise UnknownCommandError(command, 'run', suggested_commands)
            sys.stderr.write("We're assuming the '%s' command is '%s' and we're executing it for you.\n\n" % (command, suggested_commands[0]))
            command = suggested_commands[0]

        handler = self._mach_registrar.command_handlers.get(command)

        # FUTURE
        # If we wanted to conditionally enable commands based on whether
        # it's possible to run them given the current state of system, here
        # would be a good place to hook that up.

        # We create a new parser, populate it with the command's arguments,
        # then feed all remaining arguments to it, merging the results
        # with ourselves. This is essentially what argparse subparsers
        # do.

        parser_args = {
            'add_help': False,
            'usage': '%(prog)s [global arguments] ' + command +
                ' [command arguments]',
        }

        if handler.parser:
            subparser = handler.parser
        else:
            subparser = argparse.ArgumentParser(**parser_args)

        remainder = None

        for arg in handler.arguments:
            if arg[1].get('nargs') == argparse.REMAINDER:
                # parse_known_args expects all argparse.REMAINDER ('...')
                # arguments to be all stuck together. Instead, we want them to
                # pick any extra argument, wherever they are.
                # Assume a limited CommandArgument for those arguments.
                assert len(arg[0]) == 1
                assert all(k in ('default', 'nargs', 'help') for k in arg[1])
                remainder = arg
            else:
                subparser.add_argument(*arg[0], **arg[1])

        # We define the command information on the main parser result so as to
        # not interfere with arguments passed to the command.
        setattr(namespace, 'mach_handler', handler)
        setattr(namespace, 'command', command)

        command_namespace, extra = subparser.parse_known_args(args)
        setattr(namespace, 'command_args', command_namespace)
        if remainder:
            (name,), options = remainder
            # parse_known_args usefully puts all arguments after '--' in
            # extra, but also puts '--' there. We don't want to pass it down
            # to the command handler. Note that if multiple '--' are on the
            # command line, only the first one is removed, so that subsequent
            # ones are passed down.
            if '--' in extra:
                extra.remove('--')

            # Commands with argparse.REMAINDER arguments used to force the
            # other arguments to be '+' prefixed. If a user now passes such
            # an argument, if will silently end up in extra. So, check if any
            # of the allowed arguments appear in a '+' prefixed form, and error
            # out if that's the case.
            for args, _ in handler.arguments:
                for arg in args:
                    arg = arg.replace('-', '+', 1)
                    if arg in extra:
                        raise UnrecognizedArgumentError(command, [arg])

            if extra:
                setattr(command_namespace, name, extra)
            else:
                setattr(command_namespace, name, options.get('default', []))
        elif extra:
            raise UnrecognizedArgumentError(command, extra)

    def _handle_main_help(self, parser, verbose):
        # Since we don't need full sub-parser support for the main help output,
        # we create groups in the ArgumentParser and populate each group with
        # arguments corresponding to command names. This has the side-effect
        # that argparse renders it nicely.
        r = self._mach_registrar
        disabled_commands = []

        cats = [(k, v[2]) for k, v in r.categories.items()]
        sorted_cats = sorted(cats, key=itemgetter(1), reverse=True)
        for category, priority in sorted_cats:
            group = None

            for command in sorted(r.commands_by_category[category]):
                handler = r.command_handlers[command]

                # Instantiate a handler class to see if it should be filtered
                # out for the current context or not. Condition functions can be
                # applied to the command's decorator.
                if handler.conditions:
                    if handler.pass_context:
                        instance = handler.cls(self._context)
                    else:
                        instance = handler.cls()

                    is_filtered = False
                    for c in handler.conditions:
                        if not c(instance):
                            is_filtered = True
                            break
                    if is_filtered:
                        description = handler.description
                        disabled_command = {'command': command, 'description': description}
                        disabled_commands.append(disabled_command)
                        continue

                if group is None:
                    title, description, _priority = r.categories[category]
                    group = parser.add_argument_group(title, description)

                description = handler.description
                group.add_argument(command, help=description,
                    action='store_true')

        if disabled_commands and 'disabled' in r.categories:
            title, description, _priority = r.categories['disabled']
            group = parser.add_argument_group(title, description)
            if verbose == True:
                for c in disabled_commands:
                    group.add_argument(c['command'], help=c['description'],
                                       action='store_true')

        parser.print_help()

    def _handle_subcommand_help(self, parser, command):
        handler = self._mach_registrar.command_handlers.get(command)

        if not handler:
            raise UnknownCommandError(command, 'query')

        # This code is worth explaining. Because we are doing funky things with
        # argument registration to allow the same option in both global and
        # command arguments, we can't simply put all arguments on the same
        # parser instance because argparse would complain. We can't register an
        # argparse subparser here because it won't properly show help for
        # global arguments. So, we employ a strategy similar to command
        # execution where we construct a 2nd, independent ArgumentParser for
        # just the command data then supplement the main help's output with
        # this 2nd parser's. We use a custom formatter class to ignore some of
        # the help output.
        parser_args = {
            'formatter_class': CommandFormatter,
            'add_help': False,
        }

        if handler.parser:
            c_parser = handler.parser
            c_parser.formatter_class = NoUsageFormatter
            # Accessing _action_groups is a bit shady. We are highly dependent
            # on the argparse implementation not changing. We fail fast to
            # detect upstream changes so we can intelligently react to them.
            group = c_parser._action_groups[1]

            # By default argparse adds two groups called "positional arguments"
            # and "optional arguments". We want to rename these to reflect standard
            # mach terminology.
            c_parser._action_groups[0].title = 'Command Parameters'
            c_parser._action_groups[1].title = 'Command Arguments'

            if not handler.description:
                handler.description = c_parser.description
                c_parser.description = None
        else:
            c_parser = argparse.ArgumentParser(**parser_args)
            group = c_parser.add_argument_group('Command Arguments')

        for arg in handler.arguments:
            group.add_argument(*arg[0], **arg[1])

        # This will print the description of the command below the usage.
        description = handler.description
        if description:
            parser.description = description

        parser.usage = '%(prog)s [global arguments] ' + command + \
            ' [command arguments]'
        parser.print_help()
        print('')
        c_parser.print_help()

class NoUsageFormatter(argparse.HelpFormatter):
    def _format_usage(self, *args, **kwargs):
        return ""