What do we do if user does not have kernel installed when running/opening a notebook

[DonJayamanne]

@claudiaregio /cc
Looks like we're running into this a lot

Proposed Solution/Questions:

• Display non modal error message letting them know they do not have Python installed & would need it
  • Display a message similar to what Python extnsion displays
    Python is not installed. Please download and install Python before using the extension
• Should this be a modal dialog
  • Probably not, nothing much the user can do apart from see the error and install it themselves.
  • Modal would probably make sense if we had a solution, all we can do here is provide a link.

Questions

• User opens a .NET notebook & user doesn't have .NET kernel installed
  • What do we do?
• User opens an R notebook & user doesn't have R kernel installed
  • What do we do?
  • Similar to .NET, but what if we don't kow about extensions that support Jupyter notebooks and have VS Code kernels for some languages? (e.g. we should not hardcode .NET, but how do we address it).
  • I guess this can only be done with some hardcoding
• User opens a Python notebook and they don't have ANY kernel specs, and no python installed

@jmew /cc

[rchiodo]

Ideas?

• Use piodide. Yeah okay this is silly but might be good enough?
• Offer to install python (well bring up a link to python.org)
• Warn them that the kernel won't work

[DonJayamanne]

arn them that the kernel won't work

Shouldn't we do the same for other non-python kernels? Let them know that they do not have a kernel installed that can handle this (only for non-pytohn kernels)

[rchiodo]

Shouldn't we do the same for other non-python kernels? Let them know that they do not have a kernel installed that can handle this (only for non-pytohn kernels)

Yeah that sounds like a good idea.

[joyceerhl]

@DonJayamanne in this case, wouldn't the user not have any kernel selected for the current notebook? How is this a kernel start issue then? Under the kernel push model the user shouldn't even have access to the run button.

[greazer]

We need at minimum an error message that gives some direction to the user. Especially if they don't have Python installed at all.

[DonJayamanne]

This will require a lot of changes, hence moving back to backlog and leaving assigned so we discuss the technical implementation.

[rchiodo]

We could

• always return the python default kernel
• always have the same id for this default kernel (per URI?) same guid forever?
• update this with the state of the actual preferred one when we find it
• this same kernel would be used if there's no python/no python extension

[DonJayamanne]

• If python is not installed have a kernel named Python 3
  • When user selects this and attempts to run the cell they'll be asked to either install Python extension or Python runtime
  • After installing Python extension (if python runtime is installed) user should not have to reload VS Code (the interpreters should be listed)
  • After installing Python, user will need to reload VS Code
  • TODO: File for API when this is detected by core extension.
• For non python kernels
  • Do nothing, no point stating the obvious (the user won't see the kernel in the kernel picker, hence why add another way to state this fact)
• What if user doesn't have any kernel spec?
  • Assume they are attempting to run R or something similar & just install this extension. How do they know they need to install a kernel. I.e. how do new users get started?

[DonJayamanne]

Upstream feature requests:

• Expose API for when the list of interpreters have changed vscode-python#16676
• Expose API to determine when user installs Python vscode-python#16675