Automatically install or update ocaml-lsp-server

[PizieDust]

Currently, when ocaml-lsp-server is not found in a sandbox, the language server displays an error and fails to start.
This PR improves users experience by providing a UI that asks if they will like to install or update ocaml-lsp-server or select another sandbox.

If the user wants to select another sandbox, a quickpick will be displayed with various switches.
If the user decides to install ocaml-lsp-server, it will be installed in the background and they can continue with their activities in the editor.

This PR will streamline the process for complete beginners and also reduce the time to terminal for experienced users who often will have to switch to the terminal to install ocaml-lsp-server in their sandbox.

cc @voodoos

[voodoos]

Thanks Pizie, this looks quite reasonable and works great.

I understand now the "notifications" you were talking about earlier:

Maybe we could improve the message of the "Installing sandbox packages" to also mention the name of the packages so that we could remove the additional "Installing the latest release of...." notification ?

[PizieDust]

Thanks Pizie, this looks quite reasonable and works great.

I understand now the "notifications" you were talking about earlier:

Maybe we could improve the message of the "Installing sandbox packages" to also mention the name of the packages so that we could remove the additional "Installing the latest release of...." notification ?

Thank you. This is done in the latest commit.

[voodoos]

I have one concern with the current behavior: what install package does is:

$ update --switch=5.3.0
$ install --switch=5.3.0 -y ocaml-lsp-server

There is nothing fundamentally wrong with that, but I think the second command will also upgrade every upgradable package in the switch. This might be something we want to skip to prevent potentially breaking user projects ? (not sure if that is doable however) 

edit: Just tested it, and opam is not upgrading the switch by default, so we are all good here.

[voodoos]

Looks very good. I have a few suggestions left for the upgrades 🙂

[voodoos]

I think it would be much better to modify Sandbox.upgrade_packages to accept a list of packages to upgrade and use that.

That way you wouldn't have to carry the 'latest_version' around and concatenate strings to try to install the latest version. Opam knows how to do that better :-)

You might want to rename Sandbox.upgrade_packages to Sandbox.upgrade_all_packages and then introduce the specialized Sandbox.upgrade_packages to work on a given list of packages.

[voodoos]

Thanks a lot Pizie, that looks quite close to being ready :-)