Flags and Aliases on Extensions are failing

[echarles]

Defining flags (or aliases) on Sever Extension have shown not to be working at different places:

• simple extension example #117
• JupyterLab as Server Extension jupyterlab/jupyterlab#7416
• [MRG] add open_browser trait to ExtensionApp #128

This is opened to [1] Confirm the issue [2] Define a fix.

[echarles]

There are 2 aspects here:

• Does it make sense that the base Extension imports the flags and alias from jupyter_server.serverapp as it does not extend it. Probably yes as we want to extension to influence the global ServerApp
• Launching with a flag or a alias via the entrypoint works (e.g. jupyter simple-ext11 --hello) however launching via jupyter server --ServerApp.jpserver_extensions="{'simple_ext11': True}" --hello fails with Unrecognized flag: '--hello'

[echarles]

Discussing this at the server weekly meeting, @Zsailer confirmed it was the expected behavior (you need to start with the entrypoint to have the flags operational). Closing this issue.