404 Error after upgrading from Notebook 6.5 to Notebook7.0.0rc2

404 GET /lab/api/settings/@jupyter-notebook/application-extension:shell?1687798647746 (::1): Schema not found: C:/Users/lenovo/AppData/Roaming/Python/share/jupyter/lab/schemas\@jupyter-notebook/application-extension\shell.json
[W 2023-06-27 00:57:27.756 LabApp] wrote error: 'Schema not found: C:/Users/lenovo/AppData/Roaming/Python/share/jupyter/lab/schemas\\@jupyter-notebook/application-extension\\shell.json'
Traceback (most recent call last):
File "D:\anaconda3\lib\site-packages\tornado\web.py", line 1711, in _execute
result = method(*self.path_args, **self.path_kwargs)
File "D:\anaconda3\lib\site-packages\tornado\web.py", line 3208, in wrapper
return method(self, *args, **kwargs)
File "C:\Users\lenovo\AppData\Roaming\Python\Python310\site-packages\jupyterlab_server\settings_handler.py", line 48, in get
result, warnings = get_settings(
File "C:\Users\lenovo\AppData\Roaming\Python\Python310\site-packages\jupyterlab_server\settings_utils.py", line 370, in get_settings
schema, version = _get_schema(schemas_dir, schema_name, overrides, labextensions_path)
File "C:\Users\lenovo\AppData\Roaming\Python\Python310\site-packages\jupyterlab_server\settings_utils.py", line 47, in _get_schema
raise web.HTTPError(404, notfound_error % path)
tornado.web.HTTPError: HTTP 404: Not Found (Schema not found: C:/Users/lenovo/AppData/Roaming/Python/share/jupyter/lab/schemas\@jupyter-notebook/application-extension\shell.json)
[W 2023-06-27 00:57:27.762 LabApp] 404 GET /lab/api/settings/@jupyter-notebook/application-extension:shell?1687798647746 (298c5db38adf4e708fbe9e62b888a982@::1) 12.96ms referer=http://localhost:8888/tree

Start with jupyterlab_server/settings_handler.py and settings_utils.py, especially the get_settings and _get_schema calls shown in the traceback. Reproduce the Notebook 6.5 to 7.0.0rc2 upgrade on Windows and trace why the application-extension shell schema is missing; done means the settings request no longer returns a 404.

Written by the indexing model from the issue text.