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""" Custom argparse actions """
import sys
import argparse
from Bcfg2.Options.Parser import get_parser
__all__ = ["ConfigFileAction", "ComponentAction", "PluginsAction"]
class ComponentAction(argparse.Action):
""" ComponentAction automatically imports classes and modules
based on the value of the option, and automatically collects
options from the loaded classes and modules. It cannot be used by
itself, but must be subclassed, with either :attr:`mapping` or
:attr:`bases` overridden. See
:class:`Bcfg2.Options.PluginsAction` for an example.
ComponentActions expect to be given a list of class names. If
:attr:`bases` is overridden, then it will attempt to import those
classes from identically named modules within the given bases.
For instance:
.. code-block:: python
class FooComponentAction(Bcfg2.Options.ComponentAction):
bases = ["Bcfg2.Server.Foo"]
class FooLoader(object):
options = [
Bcfg2.Options.Option(
"--foo",
type=Bcfg2.Options.Types.comma_list,
default=["One"],
action=FooComponentAction)]
If "--foo One,Two,Three" were given on the command line, then
``FooComponentAction`` would attempt to import
``Bcfg2.Server.Foo.One.One``, ``Bcfg2.Server.Foo.Two.Two``, and
``Bcfg2.Server.Foo.Three.Three``. (It would also call
:func:`Bcfg2.Options.Parser.add_component` with each of those
classes as arguments.)
Note that, although ComponentActions expect lists of components
(by default; this can be overridden by setting :attr:`islist`),
you must still explicitly specify a ``type`` argument to the
:class:`Bcfg2.Options.Option` constructor to split the value into
a list.
Note also that, unlike other actions, the default value of a
ComponentAction option does not need to be the actual literal
final value. (I.e., you don't have to import
``Bcfg2.Server.Foo.One.One`` and set it as the default in the
example above; the string "One" suffices.)
"""
#: A list of parent modules where modules or classes should be
#: imported from.
bases = []
#: A mapping of ``<name> => <object>`` that components will be
#: loaded from. This can be used to permit much more complex
#: behavior than just a list of :attr:`bases`.
mapping = dict()
#: If ``module`` is True, then only the module will be loaded, not
#: a class from the module. For instance, in the example above,
#: ``FooComponentAction`` would attempt instead to import
#: ``Bcfg2.Server.Foo.One``, ``Bcfg2.Server.Foo.Two``, and
#: ``Bcfg2.Server.Foo.Three``.
module = False
#: By default, ComponentActions expect a list of components to
#: load. If ``islist`` is False, then it will only expect a
#: single component.
islist = True
#: If ``fail_silently`` is True, then failures to import modules
#: or classes will not be logged. This is useful when the default
#: is to import everything, some of which are expected to fail.
fail_silently = False
def __init__(self, *args, **kwargs):
if self.mapping:
if 'choices' not in kwargs:
kwargs['choices'] = self.mapping.keys()
self._final = False
argparse.Action.__init__(self, *args, **kwargs)
def _import(self, module, name):
""" Import the given name from the given module, handling
errors """
try:
return getattr(__import__(module, fromlist=[name]), name)
except (AttributeError, ImportError):
if not self.fail_silently:
print("Failed to load %s from %s: %s" %
(name, module, sys.exc_info()[1]))
return None
def _load_component(self, name):
""" Import a single class or module, adding it as a component to
the parser.
:param name: The name of the class or module to import, without
the base prepended.
:type name: string
:returns: the imported class or module
"""
cls = None
if self.mapping and name in self.mapping:
cls = self.mapping[name]
elif "." in name:
cls = self._import(*name.rsplit(".", 1))
else:
for base in self.bases:
if self.module:
mod = base
else:
mod = "%s.%s" % (base, name)
cls = self._import(mod, name)
if cls is not None:
break
if cls:
get_parser().add_component(cls)
else:
print("Could not load component %s" % name)
return cls
def finalize(self, parser, namespace):
""" Finalize a default value by loading the components given
in it. This lets a default be specified with a list of
strings instead of a list of classes. """
if not self._final:
self.__call__(parser, namespace, self.default)
def __call__(self, parser, namespace, values, option_string=None):
if values is None:
result = None
else:
if self.islist:
result = []
for val in values:
cls = self._load_component(val)
if cls is not None:
result.append(cls)
else:
result = self._load_component(values)
self._final = True
setattr(namespace, self.dest, result)
class ConfigFileAction(argparse.Action):
""" ConfigFileAction automatically loads and parses a
supplementary config file (e.g., ``bcfg2-web.conf`` or
``bcfg2-lint.conf``). """
def __call__(self, parser, namespace, values, option_string=None):
get_parser().add_config_file(self.dest, values)
setattr(namespace, self.dest, values)
class PluginsAction(ComponentAction):
""" :class:`Bcfg2.Options.ComponentAction` subclass for loading
Bcfg2 server plugins. """
bases = ['Bcfg2.Server.Plugins']
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