z2h/notebook 7.0.0rc2 users redirected to tree even though defaultUrl is set to lab

[shaneknapp]

Description

basic environment: jupyterhub 4.0.1/jupyterlab 4.0.2/jupyter-notebook 7.0.0rc2

i followed the z2h instructions to set the default environment to jupyterlab.

here is that relevant bit in our config: https://github.com/berkeley-dsep-infra/datahub/blob/staging/deployments/data100-jl4/config/common.yaml#L41

when logging in, however, all users are by default sent to tree:

you can only access lab via the drop down menu:

checking the logs ( kubectl -n data100-jl4-staging logs -f jupyter-sknapp), i see that defaultUrl is being correctly passed to the container at startup:

[I 2023-06-27 18:12:47.820 JupyterHubSingleUser] Starting jupyterhub single-user server extension version 4.0.1
[I 2023-06-27 18:12:47.820 JupyterHubSingleUser] Using default url from environment $JUPYTERHUB_DEFAULT_URL: /lab
[I 2023-06-27 18:12:47.823 ServerApp] jupyterhub | extension was successfully linked.

and when the server is ready, it reports back that it's using /lab as the default -- but at the end of this snippet i'm redirected to /tree instead:

[I 2023-06-27 18:12:48.031 ServerApp] Serving notebooks from local directory: /home/jovyan
[I 2023-06-27 18:12:48.032 ServerApp] Jupyter Server 2.6.0 is running at:
[I 2023-06-27 18:12:48.032 ServerApp] http://jupyter-sknapp:8888/user/sknapp/lab?token=...
[I 2023-06-27 18:12:48.032 ServerApp]     http://127.0.0.1:8888/user/sknapp/lab?token=...
[I 2023-06-27 18:12:48.032 ServerApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
<snip one useless line of output>
[I 2023-06-27 18:12:49.921 ServerApp] 302 GET /user/sknapp/oauth_callback?code=[secret]&state=[secret] -> /user/sknapp/ (@10.0.0.43) 43.15ms
[I 2023-06-27 18:12:49.972 ServerApp] 302 GET /user/sknapp/ -> /user/sknapp/tree (sknapp@10.0.0.43) 1.54ms
[I 2023-06-27 18:12:50.035 ServerApp] 200 GET /user/sknapp/tree (sknapp@10.0.0.43) 12.71ms

i believe this is happening as a consequence of this PR: https://github.com/jupyter/notebook/pull/6941/files

Reproduce

1. install notebook 7.0.0rc1 or 7.0.0rc2, JL 4+, JH4+
2. set your jupyterhub default interface to JupyterLab
3. launch and log in to your container
4. notice you're not in jupyterlab

Expected behavior

respect defaultUrl when set in the jupyterhub deployment config.

Context

notebook 7.0.0rc1 or 7.0.0rc2, JL 4+, JH4+

here's our image config: https://github.com/berkeley-dsep-infra/datahub/blob/staging/deployments/data100-jl4/image/environment.yml

[RRosio]

Pinging @jtpio here. The PR may have caused a regression.

[jtpio]

Thanks @shaneknapp for reporting.

#6941 does look related indeed. However it also fixed #6940. So not sure the change could just be reverted as it will very likely bring #6940 back.

[mcrutch]

Maybe related, the base-notebook image which is configured to run lab, defaults the url to /tree as well, which is unexpected.

[vwbusguy]

Yup, we spent a good part of our day here trying to track down what was going on with this. This is indeed very unexpected behavior.

[jtpio]

Looking into this in #6997.