Added support for exposing EventHandlers and RegisterEventHandler actions

launch/launch/actions/register_event_handler.py

@@ -21,10 +21,14 @@
 
 from ..action import Action
 from ..event_handler import BaseEventHandler
+from ..frontend import Entity
+from ..frontend import expose_action
+from ..frontend import Parser  # noqa: F401
 from ..launch_context import LaunchContext
 from ..launch_description_entity import LaunchDescriptionEntity
 
 
+@expose_action('register_event_handler')
 class RegisterEventHandler(Action):
     """
     Action that registers an event handler.
@@ -43,6 +47,13 @@ def __init__(self, event_handler: BaseEventHandler, **kwargs) -> None:
         super().__init__(**kwargs)
         self.__event_handler = event_handler
 
+    @classmethod
+    def parse(cls, entity: Entity, parser: Parser):
+        """Return `RegisterEventHandler` action and kwargs for constructing it."""
+        _, kwargs = super().parse(entity, parser)
+
+        return cls, kwargs
+
     @property
     def event_handler(self) -> BaseEventHandler:
         """Getter for self.__event_handler."""

launch/launch/frontend/expose.py

@@ -21,6 +21,7 @@
 from typing import Text
 
 from ..action import Action
+from ..event_handler import EventHandler
 from ..some_substitutions_type import SomeSubstitutionsType
 from ..substitution import Substitution
 
@@ -29,6 +30,7 @@
     from .parser import Parser  # noqa: F401
 
 action_parse_methods = {}
+event_handler_parse_methods = {}
 substitution_parse_methods = {}
 
 
@@ -40,6 +42,14 @@ def instantiate_action(entity: 'Entity', parser: 'Parser') -> Action:
     return action_type(**kwargs)
 
 
+def instantiate_event_handler(entity: 'Entity', parser: 'Parser') -> EventHandler:
+    """Call the registered parsing method for the `Entity`."""
+    if entity.type_name not in event_handler_parse_methods:
+        raise RuntimeError('Unrecognized entity of the type: {}'.format(entity.type_name))
+    event_handler_type, kwargs = event_handler_parse_methods[entity.type_name](entity, parser)
+    return event_handler_type(**kwargs)
+
+
 def instantiate_substitution(
     type_name: Text,
     args: Optional[Iterable[SomeSubstitutionsType]] = None
@@ -128,3 +138,12 @@ def expose_action(name: Text):
     Read __expose_impl documentation.
     """
     return __expose_impl(name, action_parse_methods, 'action')
+
+
+def expose_event_handler(name: Text):
+    """
+    Return a decorator for exposing an event handler.
+
+    Read __expose_impl documentation.
+    """
+    return __expose_impl(name, event_handler_parse_methods, 'event_handler')