# (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__) @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. ########################################################################### 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 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 ############################################################## 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 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. ########################################################################### 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) def disconnect_extension_point_traits(self): """Disconnect all of the plugin's extension points.""" ExtensionPoint.disconnect_extension_point_traits(self) 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) 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})"