Recurse and get the last value when in warn mode

tractor/trionics/_broadcast.py

@@ -215,19 +215,23 @@ class BroadcastReceiver(ReceiveChannel):
                 # return this value."
                 # https://docs.rs/tokio/1.11.0/tokio/sync/broadcast/index.html#lagging
 
+                mxln = state.maxlen
+                lost = seq - mxln
+
                 # decrement to the last value and expect
                 # consumer to either handle the ``Lagged`` and come back
                 # or bail out on its own (thus un-subscribing)
-                state.subs[key] = state.maxlen - 1
+                state.subs[key] = mxln - 1
 
                 # this task was overrun by the producer side
                 task: Task = current_task()
-                msg = f'Task {task.name} was overrun'
+                msg = f'Task `{task.name}` overrun and dropped `{lost}` values'
 
                 if self._raise_on_lag:
                     raise Lagged(msg)
                 else:
                     log.warning(msg)
+                    return self.receive_nowait(_key, _state)
 
             state.subs[key] -= 1
             return value