Expose API for when the list of interpreters have changed

[brettcannon]

Discussed in #16683

^{Originally posted by DonJayamanne July 13, 2021}
Currently there's no way for Jupyter to know when user creates a new Python environment (conda, or the like).

Is it possible to get an event so we know that new interpreters have been created.

Note: Once thats done, how would we get these new interpreters. Not sure the GetInterrpeters is the best API for this, as that will return all interpreters all over again. Personally it would be nice to have something we can subscribe to, like an observable, this way we only get whats new).

[DonJayamanne]

ersonally it would be nice to have something we can subscribe to, like an observable, this way we only get whats new).

Yup, that was my original plan for how the interpreters could be exposed.
#3023

Having an observable is a very efficient way for Jupyter as well. E.g. we don't need to wait till we get all interpreters just to know that the user has an interpreter, similarly when we search for kernels we don't need to wait for all when we can start searching incrementally. (these were some of the perf improvements we discussed when looking at the delays in Jupyter extension)

[brettcannon]

Thanks for the feature request! We are going to give the community 60 days from when this issue was created to provide 5 👍 upvotes on the opening comment to gauge general interest in this idea. If there's enough upvotes then we will consider this feature request in our future planning. If there's unfortunately not enough upvotes then we will close this issue.