From eddfdc64757ab65112bf510c2842716ab6b032e3 Mon Sep 17 00:00:00 2001
From: Xiao Chen <xiao.chen@example.com>
Date: Fri, 10 Jun 2022 15:02:05 -0700
Subject: [PATCH] Chekc self.keys before trait_metadata in set_state

---
 python/ipywidgets/ipywidgets/widgets/tests/test_set_state.py | 4 ++--
 python/ipywidgets/ipywidgets/widgets/widget.py               | 4 ++--
 python/jupyterlab_widgets/src/manager.ts                     | 1 +
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/python/ipywidgets/ipywidgets/widgets/tests/test_set_state.py b/python/ipywidgets/ipywidgets/widgets/tests/test_set_state.py
index 6d8a8abebb..bee5cac16a 100644
--- a/python/ipywidgets/ipywidgets/widgets/tests/test_set_state.py
+++ b/python/ipywidgets/ipywidgets/widgets/tests/test_set_state.py
@@ -304,8 +304,8 @@ class ValueWidget(Widget):
     assert widget.value == 1
 
     widget._send = mock.MagicMock()
-    # this mimics a value coming from the front end
-    widget.set_state({'value': 42})
+    # this mimics a state coming from the front end
+    widget.set_state({'value': 42, 'unexpected_field': 43})
     assert widget.value == 42
 
     # we expect this to be echoed
diff --git a/python/ipywidgets/ipywidgets/widgets/widget.py b/python/ipywidgets/ipywidgets/widgets/widget.py
index a57d45a8da..703ac64a6d 100644
--- a/python/ipywidgets/ipywidgets/widgets/widget.py
+++ b/python/ipywidgets/ipywidgets/widgets/widget.py
@@ -566,8 +566,8 @@ def set_state(self, sync_data):
         # Send an echo update message immediately
         if JUPYTER_WIDGETS_ECHO:
             echo_state = {}
-            for attr,value in sync_data.items():
-                if self.trait_metadata(attr, 'echo_update', default=True):
+            for attr, value in sync_data.items():
+                if attr in self.keys and self.trait_metadata(attr, 'echo_update', default=True):
                     echo_state[attr] = value
             if echo_state:
                 echo_state, echo_buffer_paths, echo_buffers = _remove_buffers(echo_state)
diff --git a/python/jupyterlab_widgets/src/manager.ts b/python/jupyterlab_widgets/src/manager.ts
index 5432fe951e..e98bd4975c 100644
--- a/python/jupyterlab_widgets/src/manager.ts
+++ b/python/jupyterlab_widgets/src/manager.ts
@@ -421,6 +421,7 @@ export class WidgetManager extends LabWidgetManager {
     this._context = context;
 
     context.sessionContext.kernelChanged.connect((sender, args) => {
+      console.log('kernel changed');
       this._handleKernelChanged(args);
     });