add start and stop convenience methods to shared dispatcher

Author: rmorshea

README.md

@@ -23,7 +23,10 @@ or create a
 [pull request](https://github.com/rmorshea/idom/pulls). Thanks in advance!
 
 <h3>
-  <a href="https://mybinder.org/v2/gh/rmorshea/idom/master?filepath=notebooks%2Fintroduction.ipynb">
+  <a
+    target="_blank"
+    href="https://mybinder.org/v2/gh/idom-team/idom-jupyter/master?filepath=notebooks%2Fintroduction.ipynb"
+  >
     Try it Now
     <img alt="Binder" valign="bottom" height="25px"
     src="https://mybinder.org/badge_logo.svg"

idom/core/dispatcher.py

@@ -99,6 +99,13 @@ def __init__(self, layout: Layout) -> None:
         self._model_state: Any = {}
         self._update_queues: Dict[str, asyncio.Queue[LayoutUpdate]] = {}
 
+    async def start(self) -> None:
+        await self.__aenter__()
+
+    async def stop(self):
+        self.task_group.cancel_scope.cancel()
+        await self.__aexit__(None, None, None)
+
     @async_resource
     async def task_group(self) -> AsyncIterator[TaskGroup]:
         async with create_task_group() as group:

idom/server/sanic.py

@@ -167,13 +167,13 @@ async def _activate_dispatcher(
         self, app: Sanic, loop: asyncio.AbstractEventLoop
     ) -> None:
         self._dispatcher = cast(SharedViewDispatcher, self._make_dispatcher({}, loop))
-        await self._dispatcher.__aenter__()
+        await self._dispatcher.start()
 
     async def _deactivate_dispatcher(
         self, app: Sanic, loop: asyncio.AbstractEventLoop
     ) -> None:  # pragma: no cover
-        # this doesn't seem to get triffered during testing for some reason
-        await self._dispatcher.__aexit__(None, None, None)
+        # this doesn't seem to get triggered during testing for some reason
+        await self._dispatcher.stop()
 
     async def _run_dispatcher(
         self,