I would like it if LiveBook could update itself after I make changes to the livemd file

[Sleepful]

I am learning livebook and loving it.
There's just one scenario that I think it could support better.
Sometimes I want to jump into my editor to make some larger code changes, I can open the .livemd file easily.
However if a LiveBook process is running with the .livemd file, it will not read the changes that I make to the file outside of LiveBook, it will always overwrite it.
Is there a way around this? does it make sense to add this functionality?

Stopping the livebook process, making changes to the .livemd file and then opening the file with livebook works fine, but it is a lot of steps.

[jonatanklosko]

Hey @Sleepful :)

Unfortunately this is not trivial because Livebook autosaves the notebook to the file and it assumes that whatever it has is the source of truth. Technically we could track the last file content and try to merge the changes, however that's not something we have currently planned.

Note that you don't have to kill the whole Livebook to stop autosaving, you just need to close the session. But yeah, doing that often is not convenient.

[venkatd]

@jonatanklosko suppose the logic was "whenever the livemd file is externally modified, completely replace whatever is in livebook with what is on disk". Would a lot of complexity still remain?

I don't think merging the changes would be necessary. Most code editors choose to either keep what is in memory or replace it entirely with the version on disk.

[jonatanklosko]

Most code editors choose to either keep what is in memory or replace it entirely with the version on disk.

The difference is that with plain files, you can edit in editor A, save, open in editor B, save, open in editor A and no state is lost.

This is not the case with notebooks, because there is evaluation state (outputs, but also variables and all runtime information). Replacing the notebook from disk would have to erase all that state.

[josevalim]

@jonatanklosko I think the overall conclusion is that people is fine with state being lost, they want to see it rendered in Livebook as they work. I guess in the same way when you work with Phoenix LiveView? The state is lost but the fast reload cycle is useful. Maybe we should add some watch mode for that? Dunno.

[josevalim]

However, now I realize that, because Livebook files are Markdown files, your regular code completion likely won't work inside them anyway. In fact, it is unlikely that any tooling will provide a better completion than Livebook, as it keeps the whole environment around. So you would be effectively trading the code autocompletion by the AI one.

[venkatd]

In hindsight, I feel like keeping an externally edited .livemd file in sync with Livebook is not worth the complexity. (Except maybe the basic case of a toast "Looks like the .livemd changed, would you like to reload it and restart the session?")

I think there are alternatives.

For example, a frequent workflow of mine is:

• Connect livebook to a local node, my development environment
• VScode on one monitor, livebook on another monitor
• Prototype code in livebook
• As things stabilize, cut/paste code from livebook into vscode and recompile the local node (I have a hotkey to do this)

In this scenario, things are kept in sync without any complexity of merging. I don't lose any state because it's just calling recompile and I get to use my editor when I need.

Perhaps this and similar variations--referencing and recompiling external code--can get us most of the way there.

[venkatd]

We have a scenario where I tell someone on my team "hey can you pull the latest?". They have a running session and they tell me that nothing was updated (but really they need to kill the session and start a new session).

One idea could be to show a notification if a livebook is externally changed with the option to keep the current session or restart the session.

Thoughts?

[josevalim]

I think the detection could be helpful and less problematic than trying to merge them together.

[hugobarauna]

One idea could be to show a notification if a livebook is externally changed with the option to keep the current session or restart the session.

Livebook already has something like that but for Livebook apps (deployed notebook). If a Livebook app is opened and there's a new deployment of that app, Livebook shows a notification for that person.