Default to mix project runtime for Livebooks that live in a project

[zachallaun]

Hi friends!

Been really enjoying Livebook as a sort of notebook/scratchpad while working on projects. One quality-of-life thing that's a little annoying is having to re-connect to my mix project every time I open a new notebook.

For notebooks that live within a mix project, it would be great if the runtime would default to that project! It would save quite a large number of clicks (runtime settings -> configure -> mix standalone -> navigate your directory structure/etc. -> reconnect).

Thanks for all the work on this tool!

[josevalim]

We would need to save this information within the Livebook but it seems doable. We could have a checkbox that says: “store this for future uses”. The option can only be checked if the notebook is within the Mix directory itself.

[zachallaun]

@jonatanklosko No disagreement here.

Looking at the runtime sidebar now when you're not connected to anything, there's quite a lot of empty space. With some small tweaks to the layout, I don't think it would be crazy to have a stacked list of all the runtimes you can connect to -- Elixir standalone, Mix standalone, and Attached node -- with individual connect/configure buttons for each. If the runtime hasn't been configured, the connect button could be disabled. Clicking configure would open runtime settings directly to the appropriate tab. When you connect to a runtime, the 3 options could disappear and be replaced with the current connected runtime component.

Given the above, I think it's reasonable for the mix standalone project directory to default to the "closest" mix project based on the save location of the livebook.

This would:

1. Make it very easy to connect either to an Elixir standalone or to a Mix project
2. Not rely on any implicit defaults (all options are equally available and the default project directory is visible in the component)

[josevalim]

We have other plans for that sidebar space (node management and deployments), so we can revisit bringing Mix there in the long term if it fits, but that's certainly not the plan for now.

[zachallaun]

Thanks for the info! Given that, I think the solution you proposed here would be a sufficient quality-of-life improvement:

What we could do is to reduce the amount of clicks and detect the Mix directory in case you go to the Mix runtime tab, so you have:

  (runtime settings -> configure -> mix standalone -> [Directory already there] -> reconnect)

[josevalim]

I opened up #1278, so PRs are welcome!

[w0rd-driven]

One way to potentially mitigate this would be to use the LIVEBOOK_HOME environment variable (or the --home argument in the CLI).

When I have it set (as LIVEBOOK_HOME=.):

• runtime settings -> configure -> mix standalone -> /Users/Shared/repositories/personal/elixir/livebook_notebooks/

I can see how modifying the LIVEBOOK_HOME variable can be a little heavy-handed because it changes prompts and paths relative to this vs the user home directory.

This is only an option from the CLI though as I don't believe we can modify the desktop app's environment.

[kevinlang]

I also hit this stumbling block. I assumed that if a .livemd file was located in a mix.exs project directory, it would just automatically use the mix project runtime.