Voila handler plugin

[martinRenou]

It is currently possible to create your own template, but I find it quite limited in terms of features. What are the plans for allowing people to create their own handlers as plugins for Voila?

[SylvainCorlay]

This is more in scope for jupyter_server. You can check out the work by @Zsailer on ExtensionApp and the like.

[Zsailer]

This presents an interesting use-case I haven't considered yet—extending a server extension! Fortunately, I believe it's already possible inside the ExtensionApp class, though I'll need to do some testing.

(The comments below assume that Voila will eventually inherit the soon-to-be-merged extension API in jupyter_server.)

There are three traits in ExtensionApp that you can configure in a Voila config file to make this possible:

• handlers trait: an empty list where you can append (endpoint, handler) and jupyter_server will serve these handlers with the appropriate base_url, default_url, and static_url (if you're serving static files).
• static_paths trait: an empty list where you can append file paths to custom JS + CSS for your Voila plugin.
• template_paths trait: an empty list where you can append file paths to custom HTML templates for your plugin as well.