########################################################################
# File name: service.py
# This file is part of: aioxmpp
#
# LICENSE
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this program. If not, see
# <http://www.gnu.org/licenses/>.
#
########################################################################
import asyncio
import contextlib
import functools
import itertools
import aioxmpp.cache
import aioxmpp.callbacks
import aioxmpp.errors as errors
import aioxmpp.service as service
import aioxmpp.structs as structs
import aioxmpp.stanza as stanza
from aioxmpp.utils import namespaces
from . import xso as disco_xso
[docs]class Node(object):
"""
A :class:`Node` holds the information related to a specific node within the
entity referred to by a JID, with respect to :xep:`30` semantics.
A :class:`Node` always has at least one identity (or it will return
as ``<item-not-found/>``). It may have zero or more features beyond the
:xep:`30` features which are statically included.
To manage the identities and the features of a node, use the following
methods:
.. automethod:: register_feature
.. automethod:: unregister_feature
.. automethod:: register_identity
.. automethod:: set_identity_names
.. automethod:: unregister_identity
To access the declared features and identities, use:
.. automethod:: iter_features
.. automethod:: iter_identities
.. automethod:: as_info_xso
To access items, use:
.. automethod:: iter_items
Signals provide information about changes:
.. signal:: on_info_changed()
This signal emits when a feature or identity is registered or
unregistered.
As mentioned, bare :class:`Node` objects have no items; there are
subclasses of :class:`Node` which support items:
====================== ==================================================
:class:`StaticNode` Support for a list of :class:`.xso.Item` instances
:class:`.DiscoServer` Support for "mountpoints" for node subtrees
====================== ==================================================
"""
STATIC_FEATURES = frozenset({namespaces.xep0030_info})
on_info_changed = aioxmpp.callbacks.Signal()
def __init__(self):
super().__init__()
self._identities = {}
self._features = set()
[docs] def iter_identities(self, stanza=None):
"""
Return an iterator of tuples describing the identities of the node.
:param stanza: The IQ request stanza
:type stanza: :class:`~aioxmpp.IQ` or :data:`None`
:rtype: iterable of (:class:`str`, :class:`str`, :class:`str` or
:data:`None`, :class:`str` or :data:`None`) tuples
:return: :xep:`30` identities of this node
`stanza` can be the :class:`aioxmpp.IQ` stanza of the request. This can
be used to hide a node depending on who is asking. If the returned
iterable is empty, the :class:`~.DiscoServer` returns an
``<item-not-found/>`` error.
`stanza` may be :data:`None` if the identities are queried without
a specific request context. In that case, implementors should assume
that the result is visible to everybody.
.. note::
Subclasses must allow :data:`None` for `stanza` and default it to
:data:`None`.
Return an iterator which yields tuples consisting of the category, the
type, the language code and the name of each identity declared in this
:class:`Node`.
Both the language code and the name may be :data:`None`, if no names or
a name without language code have been declared.
"""
for (category, type_), names in self._identities.items():
for lang, name in names.items():
yield category, type_, lang, name
if not names:
yield category, type_, None, None
[docs] def iter_features(self, stanza=None):
"""
Return an iterator which yields the features of the node.
:param stanza: The IQ request stanza
:type stanza: :class:`~aioxmpp.IQ`
:rtype: iterable of :class:`str`
:return: :xep:`30` features of this node
`stanza` is the :class:`aioxmpp.IQ` stanza of the request. This can be
used to filter the list according to who is asking (not recommended).
`stanza` may be :data:`None` if the features are queried without
a specific request context. In that case, implementors should assume
that the result is visible to everybody.
.. note::
Subclasses must allow :data:`None` for `stanza` and default it to
:data:`None`.
The features are returned as strings. The features demanded by
:xep:`30` are always returned.
"""
return itertools.chain(
iter(self.STATIC_FEATURES),
iter(self._features)
)
[docs] def iter_items(self, stanza=None):
"""
Return an iterator which yields the items of the node.
:param stanza: The IQ request stanza
:type stanza: :class:`~aioxmpp.IQ`
:rtype: iterable of :class:`~.disco.xso.Item`
:return: Items of the node
`stanza` is the :class:`aioxmpp.IQ` stanza of the request. This can be
used to localize the list to the language of the stanza or filter it
according to who is asking.
`stanza` may be :data:`None` if the items are queried without
a specific request context. In that case, implementors should assume
that the result is visible to everybody.
.. note::
Subclasses must allow :data:`None` for `stanza` and default it to
:data:`None`.
A bare :class:`Node` cannot hold any items and will thus return an
iterator which does not yield any element.
"""
return iter([])
[docs] def register_feature(self, var):
"""
Register a feature with the namespace variable `var`.
If the feature is already registered or part of the default :xep:`30`
features, a :class:`ValueError` is raised.
"""
if var in self._features or var in self.STATIC_FEATURES:
raise ValueError("feature already claimed: {!r}".format(var))
self._features.add(var)
self.on_info_changed()
[docs] def register_identity(self, category, type_, *, names={}):
"""
Register an identity with the given `category` and `type_`.
If there is already a registered identity with the same `category` and
`type_`, :class:`ValueError` is raised.
`names` may be a mapping which maps :class:`.structs.LanguageTag`
instances to strings. This mapping will be used to produce
``<identity/>`` declarations with the respective ``xml:lang`` and
``name`` attributes.
"""
key = category, type_
if key in self._identities:
raise ValueError("identity already claimed: {!r}".format(key))
self._identities[key] = names
self.on_info_changed()
[docs] def set_identity_names(self, category, type_, names={}):
"""
Update the names of an identity.
:param category: The category of the identity to update.
:type category: :class:`str`
:param type_: The type of the identity to update.
:type type_: :class:`str`
:param names: The new internationalised names to set for the identity.
:type names: :class:`~.abc.Mapping` from
:class:`.structs.LanguageTag` to :class:`str`
:raises ValueError: if no identity with the given category and type
is currently registered.
"""
key = category, type_
if key not in self._identities:
raise ValueError("identity not registered: {!r}".format(key))
self._identities[key] = names
self.on_info_changed()
[docs] def unregister_feature(self, var):
"""
Unregister a feature which has previously been registered using
:meth:`register_feature`.
If the feature has not been registered previously, :class:`KeyError` is
raised.
.. note::
The features which are mandatory per :xep:`30` are always registered
and cannot be unregistered. For the purpose of unregistration, they
behave as if they had never been registered; for the purpose of
registration, they behave as if they had been registered before.
"""
self._features.remove(var)
self.on_info_changed()
[docs] def unregister_identity(self, category, type_):
"""
Unregister an identity previously registered using
:meth:`register_identity`.
If no identity with the given `category` and `type_` has been
registered before, :class:`KeyError` is raised.
If the identity to remove is the last identity of the :class:`Node`,
:class:`ValueError` is raised; a node must always have at least one
identity.
"""
key = category, type_
if key not in self._identities:
raise KeyError(key)
if len(self._identities) == 1:
raise ValueError("cannot remove last identity")
del self._identities[key]
self.on_info_changed()
[docs] def as_info_xso(self, stanza=None):
"""
Construct a :class:`~.disco.xso.InfoQuery` response object for this
node.
:param stanza: The IQ request stanza
:type stanza: :class:`~aioxmpp.IQ`
:rtype: iterable of :class:`~.disco.xso.InfoQuery`
:return: The disco#info response for this node.
The resulting :class:`~.disco.xso.InfoQuery` carries the features and
identities as returned by :meth:`iter_features` and
:meth:`iter_identities`. The :attr:`~.disco.xso.InfoQuery.node`
attribute is at its default value and may need to be set by the caller
accordingly.
`stanza` is passed to :meth:`iter_features` and
:meth:`iter_identities`. See those methods for information on the
effects.
.. versionadded:: 0.9
"""
result = disco_xso.InfoQuery()
result.features.update(self.iter_features(stanza))
result.identities[:] = (
disco_xso.Identity(
category=category,
type_=type_,
lang=lang,
name=name,
)
for category, type_, lang, name in self.iter_identities(stanza)
)
return result
[docs]class StaticNode(Node):
"""
A :class:`StaticNode` is a :class:`Node` with a non-dynamic set of items.
.. attribute:: items
A list of :class:`.xso.Item` instances. These items will be returned
when the node is queried for it’s :xep:`30` items.
It is the responsibility of the user to ensure that the set of items is
valid. This includes avoiding duplicate items.
.. automethod:: clone
"""
def __init__(self):
super().__init__()
self.items = []
def iter_items(self, stanza=None):
return iter(self.items)
[docs] @classmethod
def clone(cls, other_node):
"""
Clone another :class:`Node` and return as :class:`StaticNode`.
:param other_node: The node which shall be cloned
:type other_node: :class:`Node`
:rtype: :class:`StaticNode`
:return: A static node which has the exact same features, identities
and items as `other_node`.
The features and identities are copied over into the resulting
:class:`StaticNode`. The items of `other_node` are not copied but
merely referenced, so changes to the item *objects* of `other_node`
will be reflected in the result.
.. versionadded:: 0.9
"""
result = cls()
result._features = {
feature for feature in other_node.iter_features()
if feature not in cls.STATIC_FEATURES
}
for category, type_, lang, name in other_node.iter_identities():
names = result._identities.setdefault(
(category, type_),
aioxmpp.structs.LanguageMap()
)
names[lang] = name
result.items = list(other_node.iter_items())
return result
[docs]class DiscoServer(service.Service, Node):
"""
Answer Service Discovery (:xep:`30`) requests sent to this client.
This service implements handlers for ``…disco#info`` and ``…disco#items``
IQ requests. It provides methods to configure the contents of these
responses.
.. seealso::
:class:`DiscoClient`
for a service which provides methods to query Service Discovery
information from other entities.
The :class:`DiscoServer` inherits from :class:`~.disco.Node` to manage the
identities and features of the client. The identities and features declared
in the service using the :class:`~.disco.Node` interface on the
:class:`DiscoServer` instance are returned when a query is received for the
JID with an empty or unset ``node`` attribute. For completeness, the
relevant methods are listed here. Refer to the :class:`~.disco.Node`
documentation for details.
.. autosummary::
.disco.Node.register_feature
.disco.Node.unregister_feature
.disco.Node.register_identity
.disco.Node.unregister_identity
.. note::
Upon construction, the :class:`DiscoServer` adds a default identity with
category ``"client"`` and type ``"bot"`` to the root
:class:`~.disco.Node`. This is to comply with :xep:`30`, which specifies
that at least one identity must always be returned. Otherwise, the
service would be forced to send a malformed response or reply with
``<feature-not-implemented/>``.
After having added another identity, that default identity can be
removed.
Other :class:`~.disco.Node` instances can be registered with the service
using the following methods:
.. automethod:: mount_node
.. automethod:: unmount_node
"""
on_info_result = aioxmpp.callbacks.Signal()
def __init__(self, client, **kwargs):
super().__init__(client, **kwargs)
self._node_mounts = {
None: self
}
self.register_identity(
"client", "bot",
names={
structs.LanguageTag.fromstr("en"): "aioxmpp default identity"
}
)
@aioxmpp.service.iq_handler(
aioxmpp.structs.IQType.GET,
disco_xso.InfoQuery)
async def handle_info_request(self, iq):
request = iq.payload
try:
node = self._node_mounts[request.node]
except KeyError:
raise errors.XMPPModifyError(
condition=errors.ErrorCondition.ITEM_NOT_FOUND
)
response = node.as_info_xso(iq)
response.node = request.node
if not response.identities:
raise errors.XMPPModifyError(
condition=errors.ErrorCondition.ITEM_NOT_FOUND,
)
return response
@aioxmpp.service.iq_handler(
aioxmpp.structs.IQType.GET,
disco_xso.ItemsQuery)
async def handle_items_request(self, iq):
request = iq.payload
try:
node = self._node_mounts[request.node]
except KeyError:
raise errors.XMPPModifyError(
condition=errors.ErrorCondition.ITEM_NOT_FOUND
)
response = disco_xso.ItemsQuery()
response.items.extend(node.iter_items(iq))
return response
[docs] def mount_node(self, mountpoint, node):
"""
Mount the :class:`Node` `node` to be returned when a peer requests
:xep:`30` information for the node `mountpoint`.
"""
self._node_mounts[mountpoint] = node
[docs] def unmount_node(self, mountpoint):
"""
Unmount the node mounted at `mountpoint`.
.. seealso::
:meth:`mount_node`
for a way for mounting :class:`~.disco.Node` instances.
"""
del self._node_mounts[mountpoint]
[docs]class DiscoClient(service.Service):
"""
Provide cache-backed Service Discovery (:xep:`30`) queries.
This service provides methods to query Service Discovery information from
other entities in the XMPP network. The results are cached transparently.
.. seealso::
:class:`.DiscoServer`
for a service which answers Service Discovery queries sent to the
client by other entities.
:class:`.EntityCapsService`
for a service which uses :xep:`115` to fill the cache of the
:class:`DiscoClient` with offline information.
Querying other entities’ service discovery information:
.. automethod:: query_info
.. automethod:: query_items
To prime the cache with information, the following methods can be used:
.. automethod:: set_info_cache
.. automethod:: set_info_future
To control the size of caches, the following properties are available:
.. autoattribute:: info_cache_size
:annotation: = 10000
.. autoattribute:: items_cache_size
:annotation: = 100
.. automethod:: flush_cache
Usage example, assuming that you have a :class:`.node.Client` `client`::
import aioxmpp.disco as disco
# load service into node
sd = client.summon(aioxmpp.DiscoClient)
# retrieve server information
server_info = yield from sd.query_info(
node.local_jid.replace(localpart=None, resource=None)
)
# retrieve resources
resources = yield from sd.query_items(
node.local_jid.bare()
)
"""
on_info_result = aioxmpp.callbacks.Signal()
def __init__(self, client, **kwargs):
super().__init__(client, **kwargs)
self._info_pending = aioxmpp.cache.LRUDict()
self._info_pending.maxsize = 10000
self._items_pending = aioxmpp.cache.LRUDict()
self._items_pending.maxsize = 100
self.client.on_stream_destroyed.connect(
self._clear_cache
)
@property
def info_cache_size(self):
"""
Maximum number of cache entries in the cache for :meth:`query_info`.
This is mostly a measure to prevent malicious peers from exhausting
memory by spamming :mod:`aioxmpp.entitycaps` capability hashes.
.. versionadded:: 0.9
"""
return self._info_pending.maxsize
@info_cache_size.setter
def info_cache_size(self, value):
self._info_pending.maxsize = value
@property
def items_cache_size(self):
"""
Maximum number of cache entries in the cache for :meth:`query_items`.
.. versionadded:: 0.9
"""
return self._items_pending.maxsize
@items_cache_size.setter
def items_cache_size(self, value):
self._items_pending.maxsize = value
def _clear_cache(self):
for fut in self._info_pending.values():
if not fut.done():
fut.cancel()
self._info_pending.clear()
for fut in self._items_pending.values():
if not fut.done():
fut.cancel()
self._items_pending.clear()
def _handle_info_received(self, jid, node, task):
try:
result = task.result()
except Exception:
return
self.on_info_result(jid, node, result)
[docs] def flush_cache(self):
"""
Clear the cache.
This clears the internal cache in a way which lets existing queries
continue, but the next query for each target will behave as if
`require_fresh` had been set to true.
"""
self._info_pending.clear()
self._items_pending.clear()
async def send_and_decode_info_query(self, jid, node):
request_iq = stanza.IQ(to=jid, type_=structs.IQType.GET)
request_iq.payload = disco_xso.InfoQuery(node=node)
response = await self.client.send(request_iq)
return response
[docs] async def query_info(self, jid, *,
node=None, require_fresh=False, timeout=None,
no_cache=False):
"""
Query the features and identities of the specified entity.
:param jid: The entity to query.
:type jid: :class:`aioxmpp.JID`
:param node: The node to query.
:type node: :class:`str` or :data:`None`
:param require_fresh: Boolean flag to discard previous caches.
:type require_fresh: :class:`bool`
:param timeout: Optional timeout for the response.
:type timeout: :class:`float`
:param no_cache: Boolean flag to forbid caching of the request.
:type no_cache: :class:`bool`
:rtype: :class:`.xso.InfoQuery`
:return: Service discovery information of the `node` at `jid`.
The requests are cached. This means that only one request is ever fired
for a given target (identified by the `jid` and the `node`). The
request is re-used for all subsequent requests to that identity.
If `require_fresh` is set to true, the above does not hold and a fresh
request is always created. The new request is the request which will be
used as alias for subsequent requests to the same identity.
The visible effects of this are twofold:
* Caching: Results of requests are implicitly cached
* Aliasing: Two concurrent requests will be aliased to one request to
save computing resources
Both can be turned off by using `require_fresh`. In general, you should
not need to use `require_fresh`, as all requests are implicitly
cancelled whenever the underlying session gets destroyed.
`no_cache` can be set to true to prevent future requests to be aliased
to this request, i.e. the request is not stored in the internal request
cache. This does not affect `require_fresh`, i.e. if a cached result is
available, it is used.
The `timeout` can be used to restrict the time to wait for a
response. If the timeout triggers, :class:`TimeoutError` is raised.
If :meth:`~.Client.send` raises an
exception, all queries which were running simultanously for the same
target re-raise that exception. The result is not cached though. If a
new query is sent at a later point for the same target, a new query is
actually sent, independent of the value chosen for `require_fresh`.
.. versionchanged:: 0.9
The `no_cache` argument was added.
"""
key = jid, node
if not require_fresh:
try:
request = self._info_pending[key]
except KeyError:
pass
else:
try:
return await request
except asyncio.CancelledError:
pass
request = asyncio.ensure_future(
self.send_and_decode_info_query(jid, node)
)
request.add_done_callback(
functools.partial(
self._handle_info_received,
jid,
node
)
)
if not no_cache:
self._info_pending[key] = request
try:
if timeout is not None:
try:
result = await asyncio.wait_for(
request,
timeout=timeout)
except asyncio.TimeoutError:
raise TimeoutError()
else:
result = await request
except: # NOQA
if request.done():
try:
pending = self._info_pending[key]
except KeyError:
pass
else:
if pending is request:
del self._info_pending[key]
raise
return result
[docs] async def query_items(self, jid, *,
node=None, require_fresh=False, timeout=None):
"""
Query the items of the specified entity.
:param jid: The entity to query.
:type jid: :class:`aioxmpp.JID`
:param node: The node to query.
:type node: :class:`str` or :data:`None`
:param require_fresh: Boolean flag to discard previous caches.
:type require_fresh: :class:`bool`
:param timeout: Optional timeout for the response.
:type timeout: :class:`float`
:rtype: :class:`.xso.ItemsQuery`
:return: Service discovery items of the `node` at `jid`.
The arguments have the same semantics as with :meth:`query_info`, as
does the caching and error handling.
"""
key = jid, node
if not require_fresh:
try:
request = self._items_pending[key]
except KeyError:
pass
else:
try:
return await request
except asyncio.CancelledError:
pass
request_iq = stanza.IQ(to=jid, type_=structs.IQType.GET)
request_iq.payload = disco_xso.ItemsQuery(node=node)
request = asyncio.ensure_future(
self.client.send(request_iq)
)
self._items_pending[key] = request
try:
if timeout is not None:
try:
result = await asyncio.wait_for(
request,
timeout=timeout)
except asyncio.TimeoutError:
raise TimeoutError()
else:
result = await request
except: # NOQA
if request.done():
try:
pending = self._items_pending[key]
except KeyError:
pass
else:
if pending is request:
del self._items_pending[key]
raise
return result
[docs] def set_info_cache(self, jid, node, info):
"""
This is a wrapper around :meth:`set_info_future` which creates a future
and immediately assigns `info` as its result.
.. versionadded:: 0.5
"""
fut = asyncio.Future()
fut.set_result(info)
self.set_info_future(jid, node, fut)
[docs] def set_info_future(self, jid, node, fut):
"""
Override the cache entry (if one exists) for :meth:`query_info` of the
`jid` and `node` combination with the given :class:`asyncio.Future`
fut.
The future must receive a :class:`dict` compatible to the output of
:meth:`.xso.InfoQuery.to_dict`.
As usual, the cache can be bypassed and cleared by passing
`require_fresh` to :meth:`query_info`.
.. seealso::
Module :mod:`aioxmpp.entitycaps`
:xep:`0115` implementation which uses this method to prime the
cache with information derived from Entity Capability
announcements.
.. note::
If a future is set to exception state, it will still remain and make
all queries for that target fail with that exception, until a query
uses `require_fresh`.
.. versionadded:: 0.5
"""
self._info_pending[jid, node] = fut
[docs]class mount_as_node(service.Descriptor):
"""
Service descriptor which mounts the :class:`~.service.Service` as
:class:`.DiscoServer` node.
:param mountpoint: The mountpoint at which to mount the node.
:type mountpoint: :class:`str`
.. versionadded:: 0.8
When the service is instaniated, it is mounted as :class:`~.disco.Node` at
the given `mountpoint`; it must thus also inherit from
:class:`~.disco.Node` or implement a compatible interface.
.. autoattribute:: mountpoint
"""
def __init__(self, mountpoint):
super().__init__()
self._mountpoint = mountpoint
@property
def mountpoint(self):
"""
The mountpoint at which the node is mounted.
"""
return self._mountpoint
@property
def required_dependencies(self):
return [DiscoServer]
@contextlib.contextmanager
def init_cm(self, instance):
disco = instance.dependencies[DiscoServer]
disco.mount_node(self._mountpoint, instance)
try:
yield
finally:
disco.unmount_node(self._mountpoint)
@property
def value_type(self):
return type(None)
[docs]class RegisteredFeature:
"""
Manage registration of a feature with a :class:`DiscoServer`.
:param service: The service implementing the service discovery server.
:type service: :class:`DiscoServer`
:param feature: The feature to register.
:type feature: :class:`str`
.. note::
Normally, you would not create an instance of this object manually.
Use the :class:`register_feature` descriptor on your
:class:`aioxmpp.Service` which will provide a
:class:`RegisteredFeature` object::
class Foo(aioxmpp.Service):
_some_feature = aioxmpp.disco.register_feature(
"urn:of:the:feature"
)
# after __init__, self._some_feature is a RegisteredFeature
# instance.
@property
def some_feature_enabled(self):
# better do not expose the enabled boolean directly; this
# gives you the opportunity to do additional things when it
# is changed, such as disabling multiple features at once.
return self._some_feature.enabled
@some_feature_enabled.setter
def some_feature_enabled(self, value):
self._some_feature.enabled = value
.. versionadded:: 0.9
This object can be used as a context manager. Upon entering the context,
the feature is registered. When the context is left, the feature is
unregistered.
.. note::
The context-manager use does not nest sensibly. Thus, do not use
th context-manager feature on :class:`RegisteredFeature` instances
which are created by :class:`register_feature`, as
:class:`register_feature` uses the context manager to
register/unregister the feature on initialisation/shutdown.
Independently, it is possible to control the registration status of the
feature using :attr:`enabled`.
.. autoattribute:: enabled
.. autoattribute:: feature
"""
def __init__(self, service, feature):
self.__service = service
self.__feature = feature
self.__enabled = False
@property
def enabled(self):
"""
Boolean indicating whether the feature is registered by this object
or not.
When this attribute is changed to :data:`True`, the feature is
registered. When the attribute is changed to :data:`False`, the feature
is unregisterd.
"""
return self.__enabled
@enabled.setter
def enabled(self, value):
value = bool(value)
if value == self.__enabled:
return
if value:
self.__service.register_feature(self.__feature)
else:
self.__service.unregister_feature(self.__feature)
self.__enabled = value
@property
def feature(self):
"""
The feature this object is controlling (read-only).
"""
return self.__feature
def __enter__(self):
self.enabled = True
return self
def __exit__(self, exc_type, exc_value, tb):
self.enabled = False
[docs]class register_feature(service.Descriptor):
"""
Service descriptor which registers a service discovery feature.
:param feature: The feature to register.
:type feature: :class:`str`
.. versionadded:: 0.8
When the service is instaniated, the `feature` is registered at the
:class:`~.DiscoServer`.
On instances, the attribute which is described with this is a
:class:`RegisteredFeature` instance.
.. versionchanged:: 0.9
:class:`RegisteredFeature` was added; before, the attribute reads as
:data:`None`.
"""
def __init__(self, feature):
super().__init__()
self._feature = feature
@property
def feature(self):
"""
The feature which is registered.
"""
return self._feature
@property
def required_dependencies(self):
return [DiscoServer]
def init_cm(self, instance):
disco = instance.dependencies[DiscoServer]
return RegisteredFeature(disco, self._feature)
@property
def value_type(self):
return RegisteredFeature