open_browser=False doesn't work anymore

Up until the new version 3 c.LabApp.open_browser = False used to work when starting jupyter-lab. The setting is now c.ServerApp.open_browser and it defaults to False but a browser window is opened every time I start jupyter-lab.

[JohnPaton]

I’m encountering this issue now. I’m not able to start jupyter lab in a headless environment despite having open_browser=False in my config files:

$ pip freeze | grep jupy
jupyter-client==6.1.11
jupyter-core==4.7.1
jupyter-resource-usage==0.5.1
jupyter-server==1.4.0
jupyterlab==3.0.8
jupyterlab-pygments==0.1.2
jupyterlab-server==2.2.1
jupytext==1.10.2

$ cat ~/.jupyter/jupyter_server_config.py | grep browser
c.NotebookApp.open_browser = False
c.ServerApp.open_browser = False

$ jupyter lab
[I 2021-02-19 10:17:11.664 ServerApp] jupyter_resource_usage | extension was successfully linked.
[W 2021-02-19 10:17:11.672 LabApp] 'token' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.672 LabApp] 'password' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.672 LabApp] 'password' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.672 LabApp] 'port' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.672 LabApp] 'allow_root' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.672 LabApp] 'ip' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.672 LabApp] 'allow_origin_pat' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.673 LabApp] 'allow_remote_access' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.673 LabApp] 'disable_check_xsrf' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.673 LabApp] 'base_url' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[I 2021-02-19 10:17:11.682 ServerApp] jupyterlab | extension was successfully linked.
[I 2021-02-19 10:17:11.682 ServerApp] jupytext | extension was successfully linked.
[W 2021-02-19 10:17:11.686 NotebookApp] 'token' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.686 NotebookApp] 'password' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.686 NotebookApp] 'password' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.687 NotebookApp] 'port' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.687 NotebookApp] 'allow_root' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.687 NotebookApp] 'ip' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.687 NotebookApp] 'allow_origin_pat' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.687 NotebookApp] 'allow_remote_access' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.687 NotebookApp] 'disable_check_xsrf' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[W 2021-02-19 10:17:11.687 NotebookApp] 'base_url' has moved from NotebookApp to ServerApp. This config will be passed to ServerApp. Be sure to update your config before our next release.
[I 2021-02-19 10:17:11.971 ServerApp] nbresuse | extension was found and enabled by nbclassic. Consider moving the extension to Jupyter Server's extension paths.
[I 2021-02-19 10:17:11.971 ServerApp] nbresuse | extension was successfully linked.
[I 2021-02-19 10:17:11.971 ServerApp] nbclassic | extension was successfully linked.
[W 2021-02-19 10:17:11.990 ServerApp] All authentication is disabled.  Anyone who can connect to this server will be able to run code.
[I 2021-02-19 10:17:11.994 ServerApp] jupyter_resource_usage | extension was successfully loaded.
[I 2021-02-19 10:17:11.995 LabApp] JupyterLab extension loaded from /usr/local/lib/python3.7/site-packages/jupyterlab
[I 2021-02-19 10:17:11.995 LabApp] JupyterLab application directory is /usr/local/share/jupyter/lab
[I 2021-02-19 10:17:11.999 ServerApp] jupyterlab | extension was successfully loaded.
[I 2021-02-19 10:17:11.999 ServerApp] [Jupytext Server Extension] Deriving a JupytextContentsManager from LargeFileManager
[I 2021-02-19 10:17:12.001 ServerApp] jupytext | extension was successfully loaded.
[I 2021-02-19 10:17:12.006 ServerApp] nbclassic | extension was successfully loaded.
[W 2021-02-19 10:17:12.006 ServerApp] nbresuse | extension failed loading with message: Duplicated timeseries in CollectorRegistry: {'total_memory_usage'}
[I 2021-02-19 10:17:12.006 ServerApp] Serving notebooks from local directory: /some/directory
[I 2021-02-19 10:17:12.007 ServerApp] Jupyter Server 1.4.0 is running at:
[I 2021-02-19 10:17:12.007 ServerApp] http://localhost:8080/lab
[I 2021-02-19 10:17:12.007 ServerApp]  or http://127.0.0.1:8080/lab
[I 2021-02-19 10:17:12.007 ServerApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/jupyter_server/serverapp.py", line 2018, in launch_browser
    browser = webbrowser.get(self.browser or None)
  File "/usr/local/lib/python3.7/webbrowser.py", line 65, in get
    raise Error("could not locate runnable browser")
webbrowser.Error: could not locate runnable browser

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/bin/jupyter-lab", line 8, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.7/site-packages/jupyter_server/extension/application.py", line 520, in launch_instance
    serverapp.start()
  File "/usr/local/lib/python3.7/site-packages/jupyter_server/serverapp.py", line 2100, in start
    self.start_app()
  File "/usr/local/lib/python3.7/site-packages/jupyter_server/serverapp.py", line 2059, in start_app
    self.launch_browser()
  File "/usr/local/lib/python3.7/site-packages/jupyter_server/serverapp.py", line 2020, in launch_browser
    self.log.warning(_('No web browser found: %s.') % e)
UnboundLocalError: local variable '_' referenced before assignment

Note that I have the properties duplicated over c.NotebookApp and c.ServerApp because this config file is being used for different jupyter versions, but I don’t think that should matter.

Any ideas?

[Zsailer]

Things should be better now by upgrading jupyter_server, i.e. pip install -U jupyter_server.

You’ll temporarily get a warning that looks like:

'open_browser' is found in LabApp, NotebookApp, and ServerApp. This is a recent change.This config will only be set in LabApp. Please check if you should also config these traits in NotebookApp and ServerApp for your purpose.

until nbclassic handles this trait.