Reconsider single/double click behavior in the Notebook v7 file manager

[fperez]

Problem

As I mentioned in #6397, I think that for users who come from Classic to the Lab-based toolchain but are looking for a similar experience, the switch from single- to double-click behavior in the file manager is going to be jarring.

So I would like to have this issue for discussion of the problem, though I know this is a tricky one. Other aspects of UX parity I think are straightforward and simply a matter of implementation.

The pro argument is consistency with transition from Classic, the con one is that this really would be a big break with the behavior of Lab... I just checked what VSCode does, and it has an interesting behavior that I actually think works well (though it has an annoying inconsistency): single click opens files in a quick preview mode, but you need to double-click to leave it permanently open for editing.

The inconsistency in vscode is that some file types (like PDFs) do stay open on single click, I think the distinction is whether the file is editable or not.

I'm leaning towards the view that a more consistent version of the vscode behavior could be a good solution across Retro and Lab:

• single click does something useful immediately:
  • in Retro it fires a new tab (like Classic)
  • in Lab it opens the file in a quick preview mode (i.e. no kernel for notebooks, no render for markdown, etc). If the user clicks on a different file, it previews that one in the same tab, so the single-click action can be used to quickly "scan" a folder with many files. A file opened for preview with a single click becomes "fully active" if the user edits it while they had it open in the preview tab.
• Double-click works like it does today in Lab, no change there, and can also work the same for Retro, to help with consistency.

A bit controversial perhaps, and would need discussion in Lab as well, obviously, but I'm warming up to this as both a good transition option for Classic -> Retro in a critical part of the UX, and actually an improvement to the Lab UX (to this day I still don't like the double-click behavior of Lab, TBH).

Obviously something could be implemented here independent of Lab, but I think we should consider these decisions holistically to provide as smooth as possible an experience from classic to retro to lab.

This is also relevant to our work in berkeley-dsep-infra/datahub#2422.

[andrii-i]

jupyterlab/jupyterlab#14071 needs to be resolved in JupyterLab first.

[RRosio]

I opened jupyterlab/jupyterlab#16598 to provide the option for single click navigation in JupyterLab (disabled by default). This could either follow the same behaviour of JupyterLab or rather be enabled by default in Notebook