Allow running Notebook v7 with JupyterLab development install

[davidbrochart]

Problem

RetroLab depends on JupyterLab, but changes in JupyterLab's code are not taken into account in a development install of RetroLab.

Proposed Solution

It would be nice to have RetroLab support a jupyter retro --dev-mode that runs JupyterLab's development install.

[jtpio]

Thanks @davidbrochart.

Is the goal to be able to use local changes from unreleased @jupyterlab/ packages? And then build RetroLab with these packages?

If so then we probably need to link packages across the two repos with something like yarn link.

[davidbrochart]

Yes, that is the goal.

[brichet]

One option can be to use yalc, that act as a local package repository.

See https://github.com/jupyter/notebook/pull/7292 changes for more details.

[jtpio]

Closing as fixed by https://github.com/jupyter/notebook/pull/7292.

Feel free to open a new issue or propose improvements in a PR, thanks!