Format on save

[aladinoster]

Problem

• I am constantly switching between Jupyter Lab and VSCode just for the formatting functionality. I like a lot the possibility to format on save the code by applying formatting via black.

Proposed Solution

• Would it be possible to have an option to format on save your code available via the settings option? This could probably imply the selector of a code formatter and maybe some parameters for the configuration.

Additional context

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[fcollonval]

I would advice installing that extension: jupyterlab-code-formatter.

[bollwyvl]

We'd also like to support this for all the languages in jupyterlab-lsp but it's a bit of A Thing to support for All The Servers especially in the notebook.

[StefanBrand]

@aladinoster There are several possible workarounds. I myself now most often use VSCode myself because of its capability of formatting cells.*

Most simple: jupyter_black

I can really recommend jupyter_black. After installation you just have to run this in the first cell:

import jupyter_black

jupyter_black.load(lab= True)

All subsequent cells will be formatted after they have been run successfully.

Requires notebook reload: nbqa black

nbQA is a command line tool that not only supports black, but other formatters and linters as well. You would run nbqa black from the Terminal. Downside is that you would then have to go to "File > Reload Notebook from Disk" because JupyterLab does not automatically reload the notebook.

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* I always have to manually "Select Python Intepreter" in VSCode before formatting would work. This most probably is a peculiarity of attaching to a JupyterHub-spawned hub and simultaneously connecting to the remote kernel.

[StefanBrand]

I propose to close this issue in favor of the older jupyter-lsp/jupyterlab-lsp#632, which is also closer to where the formatting feature would probably be implemented.