Download/Upload file to/from user's file system

[TylerPachal]

Hello,

I am looking to implement a custom smart cell that would create a Download button, allowing users to export the output of a cell to a file on their file system. For example, running a database query and downloading the resulting table as a .csv.

If you could point me in the right direction I could try to implement this. I think it will require a new controller in the Livebook application to facilitate the downloading of the file, which could be opened in a new tab (relative to the livebook page). But perhaps there is a better way to implement this?

[josevalim]

I don’t think you want a smart cell, but Kino.JS or Kino.JS.Live. Then you can send the contents directly through JS. If you can’t emulate downloads via JS, then a new endpoint would be indeed necessary.

[jonatanklosko]

We can send the payload to JS and save from there, but currently we don't have a mechanism for sending a message to a specific client, only a broadcast.

[josevalim]

Ok, so an initial version would send the download to everyone but only the one clicking download needs to serve it. This is temporary until we add this feature, correct?

[jonatanklosko]

Correct!

[jonatanklosko]

I opened livebook-dev/kino#171, and there's already livebook-dev/kino#19 for Kino.Download.