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""" Classes to make it easier to create commands with large numbers of
subcommands (e.g., bcfg2-admin, bcfg2-info). """
import re
import cmd
import sys
import copy
import shlex
import logging
from Bcfg2.Compat import StringIO
from Bcfg2.Options import PositionalArgument
from Bcfg2.Options.OptionGroups import Subparser
from Bcfg2.Options.Parser import Parser, setup as master_setup
__all__ = ["Subcommand", "HelpCommand", "CommandRegistry", "register_commands"]
class Subcommand(object):
""" Base class for subcommands. This must be subclassed to create
commands.
Specifically, you must override
:func:`Bcfg2.Options.Subcommand.run`. You may want to override:
* The docstring, which will be used as the short help.
* :attr:`Bcfg2.Options.Subcommand.options`
* :attr:`Bcfg2.Options.Subcommand.help`
* :attr:`Bcfg2.Options.Subcommand.interactive`
*
* :func:`Bcfg2.Options.Subcommand.shutdown`
You should not need to override
:func:`Bcfg2.Options.Subcommand.__call__` or
:func:`Bcfg2.Options.Subcommand.usage`.
A ``Subcommand`` subclass constructor must not take any arguments.
"""
#: Options this command takes
options = []
#: Longer help message
help = None
#: Whether or not to expose this command in an interactive
#: :class:`cmd.Cmd` shell, if one is used. (``bcfg2-info`` uses
#: one, ``bcfg2-admin`` does not.)
interactive = True
_ws_re = re.compile(r'\s+', flags=re.MULTILINE)
def __init__(self):
self.core = None
description = "%s: %s" % (self.__class__.__name__.lower(),
self.__class__.__doc__)
#: The :class:`Bcfg2.Options.Parser` that will be used to
#: parse options if this subcommand is called from an
#: interactive :class:`cmd.Cmd` shell.
self.parser = Parser(
prog=self.__class__.__name__.lower(),
description=description,
components=[self],
add_base_options=False,
epilog=self.help)
self._usage = None
#: A :class:`logging.Logger` that can be used to produce
#: logging output for this command.
self.logger = logging.getLogger(self.__class__.__name__.lower())
def __call__(self, args=None):
""" Perform option parsing and other tasks necessary to
support running ``Subcommand`` objects as part of a
:class:`cmd.Cmd` shell. You should not need to override
``__call__``.
:param args: Arguments given in the interactive shell
:type args: list of strings
:returns: The return value of :func:`Bcfg2.Options.Subcommand.run`
"""
if args is not None:
self.parser.namespace = copy.copy(master_setup)
alist = shlex.split(args)
try:
setup = self.parser.parse(alist)
except SystemExit:
return sys.exc_info()[1].code
return self.run(setup)
else:
return self.run(master_setup)
def usage(self):
""" Get the short usage message. """
if self._usage is None:
sio = StringIO()
self.parser.print_usage(file=sio)
usage = self._ws_re.sub(' ', sio.getvalue()).strip()[7:]
doc = self._ws_re.sub(' ', getattr(self, "__doc__")).strip()
if doc is None:
self._usage = usage
else:
self._usage = "%s - %s" % (usage, doc)
return self._usage
def run(self, setup):
""" Run the command.
:param setup: A namespace giving the options for this command.
This must be used instead of
:attr:`Bcfg2.Options.setup` because this command
may have been called from an interactive
:class:`cmd.Cmd` shell, and thus has its own
option parser and its own (private) namespace.
``setup`` is guaranteed to contain all of the
options in the global
:attr:`Bcfg2.Options.setup` namespace, in
addition to any local options given to this
command from the interactive shell.
:type setup: argparse.Namespace
"""
raise NotImplementedError
def shutdown(self):
""" Perform any necessary shtudown tasks for this command This
is called to when the program exits (*not* when this command
is finished executing). """
pass
class HelpCommand(Subcommand):
""" Get help on a specific subcommand. This must be subclassed to
create the actual help command by overriding
:func:`Bcfg2.Options.HelpCommand.command_registry` and giving the
command access to a :class:`Bcfg2.Options.CommandRegistry`. """
options = [PositionalArgument("command", nargs='?')]
# the interactive shell has its own help
interactive = False
def command_registry(self):
""" Return a :class:`Bcfg2.Options.CommandRegistry` class.
All commands registered with the class will be included in the
help message. """
raise NotImplementedError
def run(self, setup):
commands = self.command_registry()
if setup.command:
try:
commands[setup.command].parser.print_help()
return 0
except KeyError:
print("No such command: %s" % setup.command)
for command in sorted(commands.keys()):
print(commands[command].usage())
class CommandRegistry(object):
""" A ``CommandRegistry`` is used to register subcommands and
provides a single interface to run them. It's also used by
:class:`Bcfg2.Options.HelpCommand` to produce help messages for
all available commands. """
#: A dict of registered commands. Keys are the class names,
#: lowercased (i.e., the command names), and values are instances
#: of the command objects.
commands = dict()
options = []
def runcommand(self):
""" Run the single command named in
``Bcfg2.Options.setup.subcommand``, which is where
:class:`Bcfg2.Options.Subparser` groups store the
subcommand. """
try:
return self.commands[master_setup.subcommand].run(master_setup)
finally:
self.shutdown()
def shutdown(self):
""" Perform shutdown tasks. This calls the ``shutdown``
method of all registered subcommands. """
self.commands[master_setup.subcommand].shutdown()
@classmethod
def register_command(cls, cmdcls):
""" Register a single command.
:param cmdcls: The command class to register
:type cmdcls: type
:returns: An instance of ``cmdcls``
"""
cmd_obj = cmdcls()
name = cmdcls.__name__.lower()
cls.commands[name] = cmd_obj
# py2.5 can't mix *magic and non-magical keyword args, thus
# the **dict(...)
cls.options.append(
Subparser(*cmdcls.options, **dict(name=name, help=cmdcls.__doc__)))
if issubclass(cls, cmd.Cmd) and cmdcls.interactive:
setattr(cls, "do_%s" % name, cmd_obj)
setattr(cls, "help_%s" % name, cmd_obj.parser.print_help)
return cmd_obj
def register_commands(registry, candidates, parent=Subcommand):
""" Register all subcommands in ``candidates`` against the
:class:`Bcfg2.Options.CommandRegistry` subclass given in
``registry``. A command is registered if and only if:
* It is a subclass of the given ``parent`` (by default,
:class:`Bcfg2.Options.Subcommand`);
* It is not the parent class itself; and
* Its name does not start with an underscore.
:param registry: The :class:`Bcfg2.Options.CommandRegistry`
subclass against which commands will be
registered.
:type registry: Bcfg2.Options.CommandRegistry
:param candidates: A list of objects that will be considered for
registration. Only objects that meet the
criteria listed above will be registered.
:type candidates: list
:param parent: Specify a parent class other than
:class:`Bcfg2.Options.Subcommand` that all
registered commands must subclass.
:type parent: type
"""
for attr in candidates:
try:
if (issubclass(attr, parent) and
attr != parent and
not attr.__name__.startswith("_")):
registry.register_command(attr)
except TypeError:
pass
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