Example how to save the notebook (frontend?) and get path and main metadata of the notebook (from the server side?)

[paugier]

I'd like to have an extension that adds a button (like this) to trigger a command written by the user in the metadata of the notebook.

I guess the command needs to be run on the server side because it uses the .ipynb file. The command needs to be run from the directory containing the ipynb file.

I guess the first step would be to save the notebook to be sure that the file is up to date. I didn't find that in the examples nor in other parts of the documentation (for example here https://jupyterlab.readthedocs.io/en/stable/api/modules/notebook.notebookactions.html).

How can I do that?

Then, I think I need to obtain from the server extension 2 pieces of information:

• The path of the directory where the notebook is saved
• A dictionary containing the metadata of the notebook

Is it doable? I wasn't able to find this in the examples.

Additional context

See https://discourse.jupyter.org/t/jupyterlab-extension-to-add-a-button-to-save-the-notebook-and-launch-a-command/14844/3 and https://github.com/jupyterlab/extension-examples/issues/202#issuecomment-1186516492

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