Deployed apps don't reevaluate cells marked as 'Reevaluates automatically'

[ahamez]

Environment

• Elixir & Erlang/OTP versions (elixir --version): v1.15.7
• Operating system: macOS 14.4.1
• How have you started Livebook (mix phx.server, livebook CLI, Docker, etc): macOS app
• Livebook version (use git rev-parse HEAD if running with mix): v0.12.1
• Browsers that reproduce this bug (the more the merrier): Safari, Firefox
• Include what is logged in the browser console: N/A
• Include what is logged to the server console: N/A

Current behavior

Deployed apps don't reevaluate cells marked as 'Reevaluates automatically'.

For instance, in this example, when selecting a new entry in the dropdown menu in the deployed app, the following cell is not evaluated automatically.

However, it's the case when the entry is changed in Livebook (thus, not in deployed apps).

Expected behavior

I would expect the cells to be reevaluated automatically to offer a consistent experience.

[josevalim]

@jonatanklosko do you remember why we disable reevaluate automatically for apps? I think it makes sense to keep due to the input behaviour, no?

[jonatanklosko]

@josevalim it may have been a side effect, we first had automatic reevaluation for everything (#1928), so we skipped the logic for "automatically reevaluating" cells, and then we reverted to reevaluate changes with a button (#2066), but the "automatically reevaluating" logic is still skipped. I don't remember nor couldn't find if we actually discussed "automatically reevaluating" cells specifically.

So with that context, I think it's fine to allow them. It should cover some of the use cases where reevaluating manually is awkward. And it's optional, so it doesn't break the use cases where we want to avoid eager reevaluation. Hopefully it's not confusing to have yet another behaviour in the equation, but in terms of consistency it probably makes sense.

[jonatanklosko]

Oh, looking at #2066, this test indicates it could've been intentional.

[jonatanklosko]

@josevalim perhaps initially we said that "automatically reevaluating" doesn't apply to apps and just rolled with it. Anyway, I'm ok making the change, wdyt?

[josevalim]

Agreed. I also think we forgot about the input cases and I would reenable it :)

[ahamez]

Thanks! This small change will make much easier to deploy prototype web apps 🙏