Browses disks in Livebook, uploads files to them, and adds a smart cell that builds a disk.

Mix.install([{:fil, "~> 0.2"}, {:kino, "~> 0.19"}])

disk = Fil.disk(adapter: Fil.Adapter.Local, root: "/tmp/fil")
Fil.Kino.browser(disk)

Needs Kino, an optional dependency of Fil.

Browser

browser/3 shows one directory of a disk at a time: breadcrumbs back to the root, and a table with the name, size, modification time and type of each entry. Clicking a directory opens it. Clicking a file shows a preview below the table, for images (PNG, JPEG, GIF and WebP) and text, and each file has a download button.

The browser only reads by default, so a stray click in a notebook can't change a production disk. With writable: true, each file also gets a delete button, and an upload field below the table writes into the current directory.

It lists the directory when it's shown and when you open another one, so files that other cells write show up after a click on Refresh.

It works the same on every disk. A memory disk uses the store of the process that built the browser, which in Livebook is the evaluator of the cell. Livebook evaluates all regular sections in one process, so after Fil.Adapter.Memory.checkout/0 in one cell, a browser in any regular section sees the files. A branching section has a process of its own, and needs a checkout/0 of its own.

Upload

upload/3 is a file field that writes each file you pick straight to a directory of the disk:

Fil.Kino.upload(disk, "reports", accept: [".pdf"])

Livebook keeps an upload as a file in the notebook's runtime, and the field streams it from there into Fil.write/4, so large files don't have to fit in memory. The line below the field says what was written, or why not. An upload never replaces a file unless you pass if_exists: :overwrite.

Smart cell

With Fil and Kino installed, Livebook offers a Fil disk smart cell. It's a form for a Local, S3 or Memory disk that generates the Fil.disk/1 call, such as:

disk =
  Fil.disk(
    adapter: Fil.Adapter.S3,
    bucket: "reports",
    region: "eu-central-1",
    access_key_id: System.fetch_env!("LB_AWS_ACCESS_KEY_ID"),
    secret_access_key: System.fetch_env!("LB_AWS_SECRET_ACCESS_KEY")
  )

The S3 credentials are Livebook secrets you pick in the form, so they're never part of the notebook. Without them, the disk accesses a public bucket without signing. The session token is optional, for temporary credentials such as those from AWS STS or SSO. Empty fields are left out, so the adapter's defaults apply.

The path-style switch shows what the disk does. Fil.Adapter.S3 uses path-style URLs when there's an endpoint, so the switch turns on when you enter one and off when you clear it, until you switch it the other way. The code sets path_style: only when the switch differs from that default.

For a memory disk, the cell calls Fil.Adapter.Memory.checkout/0 first. The store belongs to the evaluator (see Browser for what that means for sections), and it's gone when the runtime restarts.