/usr/lib/python3/dist-packages/cement/core/handler.py is in python3-cement 2.10.0-1.
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Cement core handler module.
"""
import re
from ..core import exc, meta
from ..core import backend
from ..utils.misc import minimal_logger
LOG = minimal_logger(__name__)
class HandlerManager(object):
"""
Manages the handler system to define, get, resolve, etc handlers with
the Cement Framework.
:param use_backend_globals: Whether to use backend globals (backward
compatibility and deprecated).
"""
def __init__(self, use_backend_globals=False):
if use_backend_globals is True:
self.__handlers__ = backend.__handlers__
else:
self.__handlers__ = {}
def get(self, handler_type, handler_label, *args):
"""
Get a handler object.
:param handler_type: The type of handler (i.e. ``output``)
:type handler_type: ``str``
:param handler_label: The label of the handler (i.e. ``json``)
:type handler_label: ``str``
:param fallback: A fallback value to return if handler_label doesn't
exist.
:returns: An uninstantiated handler object
:raises: :class:`cement.core.exc.FrameworkError`
Usage:
.. code-block:: python
output = app.handler.get('output', 'json')
output.render(dict(foo='bar'))
"""
if handler_type not in self.__handlers__:
raise exc.FrameworkError("handler type '%s' does not exist!" %
handler_type)
if handler_label in self.__handlers__[handler_type]:
return self.__handlers__[handler_type][handler_label]
elif len(args) > 0:
return args[0]
else:
raise exc.FrameworkError("handlers['%s']['%s'] does not exist!" %
(handler_type, handler_label))
def list(self, handler_type):
"""
Return a list of handlers for a given ``handler_type``.
:param handler_type: The type of handler (i.e. ``output``)
:returns: List of handlers that match ``hander_type``.
:rtype: ``list``
:raises: :class:`cement.core.exc.FrameworkError`
Usage:
.. code-block:: python
app.handler.list('log')
"""
if handler_type not in self.__handlers__:
raise exc.FrameworkError("handler type '%s' does not exist!" %
handler_type)
res = []
for label in self.__handlers__[handler_type]:
if label == '__interface__':
continue
res.append(self.__handlers__[handler_type][label])
return res
def list_types(self):
"""
Return a list of handler types (interface labels).
:returns: List of handlers types (interface labels).
:rtype: ``list``
:raises: :class:`cement.core.exc.FrameworkError`
Usage:
.. code-block:: python
app.handler.list_types()
"""
return self.__handlers__.keys()
def define(self, interface):
"""
Define a handler based on the provided interface. Defines a handler
type based on ``<interface>.IMeta.label``.
:param interface: The interface class that defines the interface to be
implemented by handlers.
:raises: :class:`cement.core.exc.InterfaceError`
:raises: :class:`cement.core.exc.FrameworkError`
Usage:
.. code-block:: python
app.handler.define(IDatabaseHandler)
"""
if not hasattr(interface, 'IMeta'):
raise exc.InterfaceError("Invalid %s, " % interface +
"missing 'IMeta' class.")
if not hasattr(interface.IMeta, 'label'):
raise exc.InterfaceError("Invalid %s, " % interface +
"missing 'IMeta.label' class.")
LOG.debug("defining handler type '%s' (%s)" %
(interface.IMeta.label, interface.__name__))
if interface.IMeta.label in self.__handlers__:
raise exc.FrameworkError("Handler type '%s' already defined!" %
interface.IMeta.label)
self.__handlers__[interface.IMeta.label] = {
'__interface__': interface
}
def defined(self, handler_type):
"""
Test whether ``handler_type`` is defined.
:param handler_type: The name or ``handler_type`` of the handler (I.e.
``log``, ``config``, ``output``, etc).
:returns: True if the handler type is defined, False otherwise.
:rtype: ``boolean``
Usage:
.. code-block:: python
app.handler.defined('log')
"""
if handler_type in self.__handlers__:
return True
else:
return False
def register(self, handler_obj, force=False):
"""
Register a handler object to a handler. If the same object is already
registered then no exception is raised, however if a different object
attempts to be registered to the same name a ``FrameworkError`` is
raised.
:param handler_obj: The uninstantiated handler object to register.
:param force: Whether to allow replacement if an existing
handler of the same ``label`` is already registered.
:raises: :class:`cement.core.exc.InterfaceError`
:raises: :class:`cement.core.exc.FrameworkError`
Usage:
.. code-block:: python
class MyDatabaseHandler(object):
class Meta:
interface = IDatabase
label = 'mysql'
def connect(self):
# ...
app.handler.register(MyDatabaseHandler)
"""
orig_obj = handler_obj
# for checks
obj = orig_obj()
if not hasattr(obj._meta, 'label') or not obj._meta.label:
raise exc.InterfaceError("Invalid handler %s, " % orig_obj +
"missing '_meta.label'.")
if not hasattr(obj._meta, 'interface') or not obj._meta.interface:
raise exc.InterfaceError("Invalid handler %s, " % orig_obj +
"missing '_meta.interface'.")
# translate dashes to underscores
orig_obj.Meta.label = re.sub('-', '_', obj._meta.label)
obj._meta.label = re.sub('-', '_', obj._meta.label)
handler_type = obj._meta.interface.IMeta.label
LOG.debug("registering handler '%s' into handlers['%s']['%s']" %
(orig_obj, handler_type, obj._meta.label))
if handler_type not in self.__handlers__:
raise exc.FrameworkError("Handler type '%s' doesn't exist." %
handler_type)
if obj._meta.label in self.__handlers__[handler_type] and \
self.__handlers__[handler_type][obj._meta.label] != orig_obj:
if force is True:
LOG.debug(
"handlers['%s']['%s'] already exists" %
(handler_type, obj._meta.label) +
", but `force==True`"
)
else:
raise exc.FrameworkError(
"handlers['%s']['%s'] already exists" %
(handler_type, obj._meta.label)
)
interface = self.__handlers__[handler_type]['__interface__']
if hasattr(interface.IMeta, 'validator'):
interface.IMeta().validator(obj)
else:
LOG.debug("Interface '%s' does not have a validator() function!" %
interface)
self.__handlers__[handler_type][obj._meta.label] = orig_obj
def registered(self, handler_type, handler_label):
"""
Check if a handler is registered.
:param handler_type: The type of handler (interface label)
:param handler_label: The label of the handler
:returns: True if the handler is registered, False otherwise
:rtype: ``boolean``
Usage:
.. code-block:: python
app.handler.registered('log', 'colorlog')
"""
if handler_type in self.__handlers__ and \
handler_label in self.__handlers__[handler_type]:
return True
return False
def resolve(self, handler_type, handler_def, **kwargs):
"""
Resolves the actual handler, as it can be either a string identifying
the handler to load from self.__handlers__, or it can be an
instantiated or non-instantiated handler class.
:param handler_type: The type of handler (aka the interface label)
:param handler_def: The handler as defined in CementApp.Meta.
:type handler_def: str, uninstantiated object, or instantiated object
:keyword raise_error: Whether or not to raise an exception if unable
to resolve the handler.
:type raise_error: boolean
:keywork meta_defaults: Optional meta-data dictionary used as
defaults to pass when instantiating uninstantiated handlers. See
``CementApp.Meta.meta_defaults``.
:returns: The instantiated handler object.
Usage:
.. code-block:: python
# via label (str)
log = app.handler.resolve('log', 'colorlog')
# via uninstantiated handler class
log = app.handler.resolve('log', ColorLogHanddler)
# via instantiated handler instance
log = app.handler.resolve('log', ColorLogHandler())
"""
raise_error = kwargs.get('raise_error', True)
meta_defaults = kwargs.get('meta_defaults', {})
han = None
if type(handler_def) == str:
han = self.get(handler_type, handler_def)(**meta_defaults)
elif hasattr(handler_def, '_meta'):
if not self.registered(handler_type, handler_def._meta.label):
self.register(handler_def.__class__)
han = handler_def
elif hasattr(handler_def, 'Meta'):
han = handler_def(**meta_defaults)
if not self.registered(handler_type, han._meta.label):
self.register(handler_def)
msg = "Unable to resolve handler '%s' of type '%s'" % \
(handler_def, handler_type)
if han is not None:
return han
elif han is None and raise_error:
raise exc.FrameworkError(msg)
elif han is None:
LOG.debug(msg)
return None
class CementBaseHandler(meta.MetaMixin):
"""Base handler class that all Cement Handlers should subclass from."""
class Meta:
"""
Handler meta-data (can also be passed as keyword arguments to the
parent class).
"""
label = None
"""The string identifier of this handler."""
interface = None
"""The interface that this class implements."""
config_section = None
"""
A config [section] to merge config_defaults with.
Note: Though Meta.config_section defaults to None, Cement will
set this to the value of ``<interface_label>.<handler_label>`` if
no section is set by the user/developer.
"""
config_defaults = None
"""
A config dictionary that is merged into the applications config
in the ``[<config_section>]`` block. These are defaults and do not
override any existing defaults under that section.
"""
overridable = False
"""
Whether or not handler can be overridden by
``CementApp.Meta.handler_override_options``. Will be listed as an
available choice to override the specific handler (i.e.
``CementApp.Meta.output_handler``, etc).
"""
def __init__(self, **kw):
super(CementBaseHandler, self).__init__(**kw)
self.app = None
def _setup(self, app_obj):
"""
The _setup function is called during application initialization and
must ``setup`` the handler object making it ready for the framework
or the application to make further calls to it.
:param app_obj: The application object.
:returns: None
"""
self.app = app_obj
if self._meta.config_section is None:
self._meta.config_section = "%s.%s" % \
(self._meta.interface.IMeta.label, self._meta.label)
if self._meta.config_defaults is not None:
LOG.debug("merging config defaults from '%s' " % self +
"into section '%s'" % self._meta.config_section)
dict_obj = dict()
dict_obj[self._meta.config_section] = self._meta.config_defaults
self.app.config.merge(dict_obj, override=False)
def get(handler_type, handler_label, *args):
"""
DEPRECATION WARNING: This function is deprecated as of Cement 2.7.x and
will be removed in future versions of Cement.
Use ``CementApp.handler.get()`` instead.
---
Get a handler object.
Required Arguments:
:param handler_type: The type of handler (i.e. 'output')
:type handler_type: str
:param handler_label: The label of the handler (i.e. 'json')
:type handler_label: str
:param fallback: A fallback value to return if handler_label doesn't
exist.
:returns: An uninstantiated handler object
:raises: cement.core.exc.FrameworkError
Usage:
from cement.core import handler
output = handler.get('output', 'json')
output.render(dict(foo='bar'))
"""
# only log debug for now as this won't be removed until Cement 3.x and
# we don't have access to CementApp.Meta.ignore_deprecation_warnings here
LOG.debug(
'Cement Deprecation Warning: `handler.get()` has been deprecated, '
'and will be removed in future versions of Cement. You should now '
'use `CementApp.handler.get()` instead.'
)
if handler_type not in backend.__handlers__:
raise exc.FrameworkError("handler type '%s' does not exist!" %
handler_type)
if handler_label in backend.__handlers__[handler_type]:
return backend.__handlers__[handler_type][handler_label]
elif len(args) > 0:
return args[0]
else:
raise exc.FrameworkError("handlers['%s']['%s'] does not exist!" %
(handler_type, handler_label))
def list(handler_type):
"""
DEPRECATION WARNING: This function is deprecated as of Cement 2.7.x and
will be removed in future versions of Cement.
Use ``CementApp.handler.list()`` instead.
---
Return a list of handlers for a given type.
:param handler_type: The type of handler (i.e. 'output')
:returns: List of handlers that match `type`.
:rtype: ``list``
:raises: cement.core.exc.FrameworkError
"""
# only log debug for now as this won't be removed until Cement 3.x and
# we don't have access to CementApp.Meta.ignore_deprecation_warnings here
LOG.debug(
'Cement Deprecation Warning: `handler.list()` has been deprecated, '
'and will be removed in future versions of Cement. You should now '
'use `CementApp.handler.list()` instead.'
)
if handler_type not in backend.__handlers__:
raise exc.FrameworkError("handler type '%s' does not exist!" %
handler_type)
res = []
for label in backend.__handlers__[handler_type]:
if label == '__interface__':
continue
res.append(backend.__handlers__[handler_type][label])
return res
def define(interface):
"""
DEPRECATION WARNING: This function is deprecated as of Cement 2.7.x and
will be removed in future versions of Cement.
Use ``CementApp.handler.define()`` instead.
---
Define a handler based on the provided interface. Defines a handler type
based on <interface>.IMeta.label.
:param interface: The interface class that defines the interface to be
implemented by handlers.
:raises: cement.core.exc.InterfaceError
:raises: cement.core.exc.FrameworkError
Usage:
.. code-block:: python
from cement.core import handler
handler.define(IDatabaseHandler)
"""
# only log debug for now as this won't be removed until Cement 3.x and
# we don't have access to CementApp.Meta.ignore_deprecation_warnings here
LOG.debug(
'Cement Deprecation Warning: `handler.define()` has been deprecated, '
'and will be removed in future versions of Cement. You should now '
'use `CementApp.handler.define()` instead.'
)
if not hasattr(interface, 'IMeta'):
raise exc.InterfaceError("Invalid %s, " % interface +
"missing 'IMeta' class.")
if not hasattr(interface.IMeta, 'label'):
raise exc.InterfaceError("Invalid %s, " % interface +
"missing 'IMeta.label' class.")
LOG.debug("defining handler type '%s' (%s)" %
(interface.IMeta.label, interface.__name__))
if interface.IMeta.label in backend.__handlers__:
raise exc.FrameworkError("Handler type '%s' already defined!" %
interface.IMeta.label)
backend.__handlers__[interface.IMeta.label] = {'__interface__': interface}
def defined(handler_type):
"""
DEPRECATION WARNING: This function is deprecated as of Cement 2.7.x and
will be removed in future versions of Cement.
Use ``CementApp.handler.defined()`` instead.
---
Test whether a handler type is defined.
:param handler_type: The name or 'type' of the handler (I.e. 'logging').
:returns: True if the handler type is defined, False otherwise.
:rtype: ``boolean``
"""
# only log debug for now as this won't be removed until Cement 3.x and
# we don't have access to CementApp.Meta.ignore_deprecation_warnings here
LOG.debug(
'Cement Deprecation Warning: `handler.defined()` has been deprecated, '
'and will be removed in future versions of Cement. You should now '
'use `CementApp.handler.defined()` instead.'
)
if handler_type in backend.__handlers__:
return True
else:
return False
def register(handler_obj, force=False):
"""
DEPRECATION WARNING: This function is deprecated as of Cement 2.7.x and
will be removed in future versions of Cement.
Use ``CementApp.handler.register()`` instead.
---
Register a handler object to a handler. If the same object is already
registered then no exception is raised, however if a different object
attempts to be registered to the same name a FrameworkError is
raised.
:param handler_obj: The uninstantiated handler object to register.
:param force: Whether to allow replacement if an existing
handler of the same ``label`` is already registered.
:raises: cement.core.exc.InterfaceError
:raises: cement.core.exc.FrameworkError
Usage:
.. code-block:: python
from cement.core import handler
class MyDatabaseHandler(object):
class Meta:
interface = IDatabase
label = 'mysql'
def connect(self):
...
handler.register(MyDatabaseHandler)
"""
# only log debug for now as this won't be removed until Cement 3.x and
# we don't have access to CementApp.Meta.ignore_deprecation_warnings here
LOG.debug(
'Cement Deprecation Warning: `handler.register()` has been '
'deprecated, and will be removed in future versions of Cement. You '
'should now use `CementApp.handler.register()` instead.'
)
orig_obj = handler_obj
# for checks
obj = orig_obj()
if not hasattr(obj._meta, 'label') or not obj._meta.label:
raise exc.InterfaceError("Invalid handler %s, " % orig_obj +
"missing '_meta.label'.")
if not hasattr(obj._meta, 'interface') or not obj._meta.interface:
raise exc.InterfaceError("Invalid handler %s, " % orig_obj +
"missing '_meta.interface'.")
# translate dashes to underscores
orig_obj.Meta.label = re.sub('-', '_', obj._meta.label)
obj._meta.label = re.sub('-', '_', obj._meta.label)
handler_type = obj._meta.interface.IMeta.label
LOG.debug("registering handler '%s' into handlers['%s']['%s']" %
(orig_obj, handler_type, obj._meta.label))
if handler_type not in backend.__handlers__:
raise exc.FrameworkError("Handler type '%s' doesn't exist." %
handler_type)
if obj._meta.label in backend.__handlers__[handler_type] and \
backend.__handlers__[handler_type][obj._meta.label] != obj:
if force is True:
LOG.debug(
"handlers['%s']['%s'] already exists" %
(handler_type, obj._meta.label) +
", but `force==True`"
)
else:
raise exc.FrameworkError(
"handlers['%s']['%s'] already exists" %
(handler_type, obj._meta.label)
)
interface = backend.__handlers__[handler_type]['__interface__']
if hasattr(interface.IMeta, 'validator'):
interface.IMeta().validator(obj)
else:
LOG.debug("Interface '%s' does not have a validator() function!" %
interface)
backend.__handlers__[handler_type][obj.Meta.label] = orig_obj
def registered(handler_type, handler_label):
"""
DEPRECATION WARNING: This function is deprecated as of Cement 2.7.x and
will be removed in future versions of Cement.
Use ``CementApp.handler.registered()`` instead.
---
Check if a handler is registered.
:param handler_type: The type of handler (interface label)
:param handler_label: The label of the handler
:returns: True if the handler is registered, False otherwise
:rtype: ``boolean``
"""
# only log debug for now as this won't be removed until Cement 3.x and
# we don't have access to CementApp.Meta.ignore_deprecation_warnings here
LOG.debug(
'Cement Deprecation Warning: `handler.registered()` has been '
'deprecated, and will be removed in future versions of Cement. You '
'should now use `CementApp.handler.registered()` instead.'
)
if handler_type in backend.__handlers__ and \
handler_label in backend.__handlers__[handler_type]:
return True
return False
def resolve(handler_type, handler_def, raise_error=True):
"""
DEPRECATION WARNING: This function is deprecated as of Cement 2.7.x and
will be removed in future versions of Cement.
Use ``CementApp.handler.resolve()`` instead.
---
Resolves the actual handler, as it can be either a string identifying
the handler to load from backend.__handlers__, or it can be an
instantiated or non-instantiated handler class.
:param handler_type: The type of handler (aka the interface label)
:param hander_def: The handler as defined in CementApp.Meta.
:type handler_def: str, uninstantiated object, or instantiated object
:param raise_error: Whether or not to raise an exception if unable
to resolve the handler.
:type raise_error: boolean
:returns: The instantiated handler object.
"""
# only log debug for now as this won't be removed until Cement 3.x and
# we don't have access to CementApp.Meta.ignore_deprecation_warnings here
LOG.debug(
'Cement Deprecation Warning: `handler.resove()` has been '
'deprecated, and will be removed in future versions of Cement. You '
'should now use `CementApp.handler.resolve()` instead.'
)
han = None
if type(handler_def) == str:
han = get(handler_type, handler_def)()
elif hasattr(handler_def, '_meta'):
if not registered(handler_type, handler_def._meta.label):
register(handler_def.__class__)
han = handler_def
elif hasattr(handler_def, 'Meta'):
han = handler_def()
if not registered(handler_type, han._meta.label):
register(handler_def)
msg = "Unable to resolve handler '%s' of type '%s'" % \
(handler_def, handler_type)
if han is not None:
return han
elif han is None and raise_error:
raise exc.FrameworkError(msg)
elif han is None:
LOG.debug(msg)
return None
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