Source code for envisage.plugin
# (C) Copyright 2007-2023 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!
""" The default implementation of the 'IPlugin' interface. """
# Standard library imports.
import logging
import os
from os.path import exists, join
# Enthought library imports.
from traits.api import Instance, List, Property, provides, Str
from traits.util.camel_case import camel_case_to_words
# Local imports.
from .extension_point import ExtensionPoint
from .extension_provider import ExtensionProvider
from .i_application import IApplication
from .i_extension_point_user import IExtensionPointUser
from .i_extension_registry import IExtensionRegistry
from .i_plugin import IPlugin
from .i_plugin_activator import IPluginActivator
from .i_service_registry import IServiceRegistry
from .i_service_user import IServiceUser
from .plugin_activator import PluginActivator
# Logging.
logger = logging.getLogger(__name__)
[docs]@provides(IPlugin, IExtensionPointUser, IServiceUser)
class Plugin(ExtensionProvider):
"""The default implementation of the 'IPlugin' interface.
This class is intended to be subclassed for each plugin that you create.
"""
#### 'IPlugin' interface ##################################################
#: The activator used to start and stop the plugin.
#:
#: By default the *same* activator instance is used for *all* plugins of
#: this type.
activator = Instance(IPluginActivator, PluginActivator())
#: The application that the plugin is part of.
application = Instance(IApplication)
#: The name of a directory (created for you) that the plugin can read and
#: write to at will.
home = Str
#: The plugin's unique identifier.
#:
#: If no identifier is specified then the module and class name of the
#: plugin are used to create an Id with the form 'module_name.class_name'.
id = Str
#: The plugin's name (suitable for displaying to the user).
#:
#: If no name is specified then the plugin's class name is used with an
#: attempt made to turn camel-case class names into words separated by
#: spaces (e.g. if the class name is 'MyPlugin' then the name would be
#: 'My Plugin'). Of course, if you really care about the actual name, then
#: just set it!
name = Str
#### 'IExtensionPointUser' interface ######################################
#: The extension registry that the object's extension points are stored in.
extension_registry = Property(Instance(IExtensionRegistry))
#### 'IServiceUser' interface #############################################
#: The service registry that the object's services are stored in.
service_registry = Property(Instance(IServiceRegistry))
#### Private interface ####################################################
# The Ids of the services that were automatically registered.
_service_ids = List
###########################################################################
# 'IExtensionPointUser' interface.
###########################################################################
def _get_extension_registry(self):
"""Trait property getter."""
return self.application
###########################################################################
# 'IServiceUser' interface.
###########################################################################
def _get_service_registry(self):
"""Trait property getter."""
return self.application
###########################################################################
# 'IExtensionProvider' interface.
###########################################################################
[docs] def get_extension_points(self):
"""Return the extension points offered by the provider."""
extension_points = [
trait.trait_type
for trait in self.traits(__extension_point__=True).values()
]
return extension_points
[docs] def get_extensions(self, extension_point_id):
"""Return the provider's extensions to an extension point."""
# Each class can have at most *one* trait that contributes to a
# particular extension point.
#
# fixme: We make this restriction in case that in future we can wire up
# the list traits directly. If we don't end up doing that then it is
# fine to allow mutiple traits!
trait_names = self.trait_names(contributes_to=extension_point_id)
if len(trait_names) == 0:
extensions = []
elif len(trait_names) == 1:
extensions = self._get_extensions_from_trait(trait_names[0])
else:
raise self._create_multiple_traits_exception(extension_point_id)
return extensions
###########################################################################
# 'IPlugin' interface.
###########################################################################
#### Trait initializers ###################################################
def _home_default(self):
"""Trait initializer."""
# Each plugin gets a sub-directory of a 'plugins' directory in
# 'application.home'.
#
# i.e. .../my.application.id/plugins/
plugins_dir = join(self.application.home, "plugins")
if not exists(plugins_dir):
os.mkdir(plugins_dir)
# Now create the 'home' directory of this plugin.
home_dir = join(plugins_dir, self.id)
if not exists(home_dir):
os.mkdir(home_dir)
return home_dir
def _id_default(self):
"""Trait initializer."""
id = "%s.%s" % (type(self).__module__, type(self).__name__)
logger.warning(
"plugin {} has no Id - using <{}>".format(
object.__repr__(self), id
)
)
return id
def _name_default(self):
"""Trait initializer."""
name = camel_case_to_words(type(self).__name__)
logger.warning(
"plugin {} has no name - using <{}>".format(
object.__repr__(self), name
)
)
return name
#### Methods ##############################################################
[docs] def start(self):
"""Start the plugin.
This method will *always* be empty so that you never have to call
'super().start()' if you provide an implementation in a
derived class.
The framework does what it needs to do when it starts a plugin by means
of the plugin's activator.
"""
pass
[docs] def stop(self):
"""Stop the plugin.
This method will *always* be empty so that you never have to call
'super().stop()' if you provide an implementation in a
derived class.
The framework does what it needs to do when it stops a plugin by means
of the plugin's activator.
"""
pass
###########################################################################
# 'Plugin' interface.
###########################################################################
[docs] def connect_extension_point_traits(self):
"""Connect all of the plugin's extension points.
This means that the plugin will be notified if and when contributions
are add or removed.
"""
ExtensionPoint.connect_extension_point_traits(self)
[docs] def disconnect_extension_point_traits(self):
"""Disconnect all of the plugin's extension points."""
ExtensionPoint.disconnect_extension_point_traits(self)
[docs] def register_services(self):
"""Register the services offered by the plugin."""
for trait_name, trait in self.traits(service=True).items():
logger.warning(
'DEPRECATED: Do not use the "service=True" metadata anymore. '
"Services should now be offered using the service "
"offer extension point (envisage.service_offers) "
"from the core plugin. "
"Plugin %s trait <%s>" % (self, trait_name)
)
# Register a service factory for the trait.
service_id = self._register_service_factory(trait_name, trait)
# We save the service Id so that so that we can unregister the
# service when the plugin is stopped.
self._service_ids.append(service_id)
[docs] def unregister_services(self):
"""Unregister any service offered by the plugin."""
# Unregister the services in the reverse order that we registered
# them.
service_ids = self._service_ids[:]
service_ids.reverse()
for service_id in service_ids:
try:
self.application.get_service_from_id(service_id)
except ValueError:
# the service may have already been individually unregistered
pass
else:
self.application.unregister_service(service_id)
# Just in case the plugin is started again!
self._service_ids = []
###########################################################################
# Private interface.
###########################################################################
#### Trait change handlers ################################################
def _anytrait_changed(self, trait_name, old, new):
"""Static trait change handler."""
# Ignore the '_items' part of the trait name (if it is there!), and get
# the actual trait.
base_trait_name = trait_name.split("_items")[0]
trait = self.trait(base_trait_name)
# If the trait is one that contributes to an extension point then fire
# an appropriate 'extension point changed' event.
if trait.contributes_to is not None:
if trait_name.endswith("_items"):
added = new.added
removed = new.removed
index = new.index
else:
added = new
removed = old
index = slice(0, len(old))
# Let the extension registry know about the change.
self._fire_extension_point_changed(
trait.contributes_to, added, removed, index
)
#### Methods ##############################################################
def _create_multiple_traits_exception(self, extension_point_id):
"""Create the exception raised when multiple traits are found."""
exception = ValueError(
"multiple traits for extension point <%s> in plugin <%s>"
% (extension_point_id, self.id)
)
return exception
def _get_extensions_from_trait(self, trait_name):
"""Return the extensions contributed via the specified trait."""
try:
extensions = getattr(self, trait_name)
except Exception:
logger.exception(
"getting extensions from %s, trait <%s>" % (self, trait_name)
)
raise
return extensions
def _get_service_protocol(self, trait):
"""Determine the protocol to register a service trait with."""
# If a specific protocol was specified then use it.
if trait.service_protocol is not None:
protocol = trait.service_protocol
# Otherwise, use the type of the objects that can be assigned to the
# trait.
#
# fixme: This works for 'Instance' traits, but what about 'AdaptsTo'
# and 'Supports' traits?
else:
# Note that in traits the protocol can be an actual class or
# interfacem or the *name* of a class or interface. This allows
# us to lazy load them!
protocol = trait.trait_type.klass
return protocol
def _register_service_factory(self, trait_name, trait):
"""Register a service factory for the specified trait."""
# Determine the protocol that the service should be registered with.
protocol = self._get_service_protocol(trait)
# Register a factory for the service so that it will be lazily loaded
# the first time somebody asks for a service with the same protocol
# (this could obviously be a lambda function, but I thought it best to
# be more explicit 8^).
def factory(**properties):
"""A service factory."""
return getattr(self, trait_name)
return self.application.register_service(protocol, factory)
###########################################################################
# 'object' interface.
###########################################################################
def __repr__(self):
"""String representation of a Plugin object"""
return f"{type(self).__name__}(id={self.id!r}, name={self.name!r})"
