docs(life-cycle): document life_cycle.on_error (#835)

Author: snacksbro

README.rst

@@ -120,9 +120,10 @@ and are prefixed with `on_*`.
 * **on_server_ready**     : All protocols initialized and available for client to connect
 * **on_client_connected** : Connection established to server
 * **on_client_exited**    : Linked to browser "beforeunload" event
+* **on_server_start**     : Trame is starting its event loop
 * **on_server_exited**    : Trame is exiting its event loop
-
 * **on_server_reload**    : If callback registered it is used for reloading server side modules
+* **on_error**            : A JavaScript error has occurred in the client, can be used to do something on the server when this occurs
 
 
 Reserved state entries

examples/validation/decorators/default_class_decorator.py

@@ -34,6 +34,10 @@ def one_slider(self, slider_value1, **kwargs):
     def on_ready(self, *args, **kwargs):
         print("on_ready")
 
+    @life_cycle.on_error
+    def on_error(self, message):
+        print(f"A JS error occured: {message}")
+
     def ui(self):
         with SinglePageLayout(self.server) as layout:
             with layout.toolbar:
@@ -47,6 +51,7 @@ def ui(self):
                 vuetify.VBtn("trigger", click="trigger('exec')")
                 vuetify.VBtn("method", click=self.method_call)
                 vuetify.VBtn("ctrl", click=self.ctrl.hello)
+                vuetify.VBtn("JS error", click="undefined_func()")
 
 
 app = App()