Notebook says to use ServerApp rather than NotebookApp in configuration, but ServerApp does not work

[lumberbot-app[bot]]

Describe the bug

I am working with the jupyter_notebook_config.py that includes a customization of the c.NotebookApp.browser (to make jupyter use chrome in app mode). This works but causes jupyter notebook to complain:

jupyter notebook
[W 2021-02-02 01:20:28.494 LabApp] 'browser' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-02 01:20:28.494 LabApp] 'browser' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.

(the message does actually occur twice).

However, trying to change the configuration property from c.NotebookApp.browser to c.ServerApp.browser (as I have it in the jupyter_lab_config.py configuration file for jupyter lab clears the complaint but does not work.

To Reproduce Steps to reproduce the behavior:

1. Ask jupyter notebook to save its configuration file with --generate-config
2. Edit the configuration file, find the (commented) c.NotebookApp.browser property, edit it and uncomment it
3. Start jupyter notebook
4. Note that the customization works but causes a complaint.
5. Change the customized property to c.ServerApp.browser`
6. Start jupyter notebook
7. See that the complaint is gone, but the property does not work.

Expected behavior If the property to use is c.NotebookApp.browser then do not complain about it. Otherwise if it is c.ServerApp.browser actually do as the property says.

Desktop (please complete the following information):

• OS: Ubuntu 20.04 (in fact kubuntu)
• Browser google-chrome

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Originally opened as jupyter/notebook#5970 by @callegar, migration requested by @Zsailer

[lumberbot-app[bot]]

@echuber2 commented: I noticed this too. It also gives a warning about some of the "NotebookApp" settings like ip and port even if I have changed them to ServerApp already.

According to the migration proposals, it sounds like we're supposed to copy jupyter_notebook_config.py (or jupyter_lab_config.py) to jupyter_server_config.py for migration, because ServerApp settings will only be read from the server config file:

https://jupyter.org/enhancement-proposals/28-jupyter-server/jupyter-server.html

When I duplicate jupter_notebook_config.py to jupyter_server_config.py and start up in lab mode (I've still been using the classic notebook interface), it does seem to use the settings, despite the remaining complaints.