Add subscription info endpoint (#16727)

* Add subscription info endpoint

* Lint

* Lint

* Make decorator

* Lint

homeassistant/components/websocket_api.py

@@ -480,6 +480,26 @@ class ActiveConnection:
         return wsock
 
 
+def async_response(func):
+    """Decorate an async function to handle WebSocket API messages."""
+    async def handle_msg_response(hass, connection, msg):
+        """Create a response and handle exception."""
+        try:
+            await func(hass, connection, msg)
+        except Exception:  # pylint: disable=broad-except
+            _LOGGER.exception("Unexpected exception")
+            connection.send_message_outside(error_message(
+                msg['id'], 'unknown', 'Unexpected error occurred'))
+
+    @callback
+    @wraps(func)
+    def schedule_handler(hass, connection, msg):
+        """Schedule the handler."""
+        hass.async_create_task(handle_msg_response(hass, connection, msg))
+
+    return schedule_handler
+
+
 @callback
 def handle_subscribe_events(hass, connection, msg):
     """Handle subscribe events command.
@@ -515,24 +535,20 @@ def handle_unsubscribe_events(hass, connection, msg):
             msg['id'], ERR_NOT_FOUND, 'Subscription not found.'))
 
 
-@callback
-def handle_call_service(hass, connection, msg):
+@async_response
+async def handle_call_service(hass, connection, msg):
     """Handle call service command.
 
     Async friendly.
     """
-    async def call_service_helper(msg):
-        """Call a service and fire complete message."""
-        blocking = True
-        if (msg['domain'] == 'homeassistant' and
-                msg['service'] in ['restart', 'stop']):
-            blocking = False
-        await hass.services.async_call(
-            msg['domain'], msg['service'], msg.get('service_data'), blocking,
-            connection.context(msg))
-        connection.send_message_outside(result_message(msg['id']))
-
-    hass.async_add_job(call_service_helper(msg))
+    blocking = True
+    if (msg['domain'] == 'homeassistant' and
+            msg['service'] in ['restart', 'stop']):
+        blocking = False
+    await hass.services.async_call(
+        msg['domain'], msg['service'], msg.get('service_data'), blocking,
+        connection.context(msg))
+    connection.send_message_outside(result_message(msg['id']))
 
 
 @callback
@@ -545,19 +561,15 @@ def handle_get_states(hass, connection, msg):
         msg['id'], hass.states.async_all()))
 
 
-@callback
-def handle_get_services(hass, connection, msg):
+@async_response
+async def handle_get_services(hass, connection, msg):
     """Handle get services command.
 
     Async friendly.
     """
-    async def get_services_helper(msg):
-        """Get available services and fire complete message."""
-        descriptions = await async_get_all_descriptions(hass)
-        connection.send_message_outside(
-            result_message(msg['id'], descriptions))
-
-    hass.async_add_job(get_services_helper(msg))
+    descriptions = await async_get_all_descriptions(hass)
+    connection.send_message_outside(
+        result_message(msg['id'], descriptions))
 
 
 @callback