feat: add the on_disconnect event

docs/events.rst

@@ -52,6 +52,7 @@ There are several different internal events:
 
     - ``raw_socket_create``
     - ``on_start``
+    - ``on_disconnect``
     - ``on_interaction``
     - ``on_command``
     - ``on_command_error``
@@ -82,6 +83,13 @@ This function takes no arguments.
 .. attention::
     Unlike ``on_ready``, this event will never be dispatched more than once.
 
+Event: ``on_disconnect``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+This event fires whenever the conenction is invalidated, and will often precede an ``on_ready`` event
+
+This function takes no arguments.
+
+
 Event: ``on_interaction``
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 This event fires on any interaction (commands, components, autocomplete and modals).

interactions/api/gateway/client.py

@@ -331,6 +331,9 @@ async def _handle_stream(self, stream: Dict[str, Any]):
             if op == OpCodeType.INVALIDATE_SESSION:
                 log.debug("INVALID_SESSION")
                 self.ready.clear()
+                self._dispatch.dispatch(
+                    "on_disconnect"
+                )  # will be followed by the on_ready event after reconnection
                 await self._reconnect(bool(data))
 
             if op == OpCodeType.RECONNECT: