Check remote node version when attaching

[linusdm]

The other day I ran into the situation that a remote node I wanted to attach to, didn't satisfy the elixir version. Since Livebook 0.8 the remote attached node should be at least 1.14.2, because there seems to be a dependency on Code.eval_quoted_with_env/4, which was introduced in elixir 1.14.2.
When connecting to a node with a lower version this results in an error raised Code.eval_quoted_with_env/4 is undefined or private.

Would it be a good idea to check the remote node version when attaching? It seems like a good point to notify the user that things will go wrong (I don't think it's possible to run any code cell, with the example above). It might be even a good idea to prevent connecting at all.
I don't think the minimal attached node version is specified anywhere right now. The versions specified in mix.exs are used for compiling the Livebook version itself (@elixir_requirement) and copying the standalone runtime (@app_elixir_version), but these versions could be different from what you expect from the attached node (at least, that's my understanding).

I've made a simple playground prototype here (mostly for my own learning). If this is at all useful, I'd be glad to polish it up, or get feedback on what would be a good way to tackle this (for example, I have no idea what would be a good place to specify this version requirement, so it's hard-coded now, which obviously is not a good idea).

An example error message could be this:

[josevalim]

Yes, a PR is welcome! I think we can check against the current Elixir version using >=

[linusdm]

Ok, great!

Can you elaborate what you mean with "the current Elixir version"? The two options in the mix.exs file I can think of are:

1. https://github.com/livebook-dev/livebook/blob/main/mix.exs#L4 this is the Elixir version requirement for the project, so it already has an operator encoded in it
2. https://github.com/livebook-dev/livebook/blob/main/mix.exs#L8 this is a plain version for the standalone elixir node, which would need to be prefixed with an operator like >=, as you suggested.

[josevalim]

I was thinking getting System.version but using the Elixir requirement should also be fine and allow for past versions, so we can start with that.

[linusdm]

fixed with #1654