Need an API to determine when Python is still busy discovering interpreters

[DonJayamanne]

Based on our previous discussions I was informed that calling refresh on the new Python API would be a noop if Python has already started the refresh. Thus we'd get a promise back letting us know if and when python has completed refreshing/loading the interpreters.
However based on the latest discussions this is not the case.

Here's what was previously discussed:

• Adopt new Python extensions non-blocking API for interpreter disocvery vscode-jupyter#7583 (comment)
  change getRefreshPromise to getRefreshPromise(): Promise | undefined;
  Where getRefreshPromise returns an existing promise instead of starting a whole new refresh. Note, refreshEnvironments is a separate method.
• The UI here also requires jupyter to know whether a refresh in Python is already in progress
  https://github.com/DonJayamanne/kernel-python-picker

This is what we need:

• If Python is busy discovering interpreters we need to know this
  It doesn't need to be a promise, it could be an event along with a status property (as previously discussed),
  This way the change even triggers when theres' a change in the state
  and a status property contains the current status refreshing|idle|etc...

@karrtikr this is something we wanted in the previous API, hence filing this as a bug.

[karrtikr]

Based on our previous discussions I was informed that calling refresh on the new Python API would be a noop if Python has already started the refresh. Thus we'd get a promise back letting us know if and when python has completed refreshing/loading the interpreters.
However based on the latest discussions this is not the case.

There's been some misunderstanding again, if Python already started a refresh and Jupyter calls the refresh API, the same promise is returned, i.e you would get a promise back letting you know if and when python has completed.

But the Python extension only starts a refresh on startup the first time the extension is loaded.

Let's discuss some alternatives, like Jupyter only automatically starting a refresh when the kernel picker is opened. My understanding is this can now be done as the kernel picker is now simply a quickpick.

[DonJayamanne]

Note: for now i'm calling the refresh method in Python Extneion API as soon as extension loads.
This is something we used to do and then removed 2 weeks ago, bringing this back now.

I don't think its good for us to call refresh unnecessarily as this could cause other I/O (perf) issues, as a discovery is invoked unnecessarily (which is somethign I hope to avoid)

[DonJayamanne]

• Refresh without force is only once per session
  • Hence calling this n additional times will have no effect
• When we have a refresh button on Kernel Quick pick we should call refresh with force
• Suggestion is to call refresh upon display of kernel quickpick
• TODO: solve issue with IW