RUN --interactive

[dchw]

Executive Summary:

Allows interactive sessions at the ends of builds; with the option to persist those changes into the result or not.

Example uses:

General:

test:
    FROM alpine:3.13
    RUN --interactive type=save ash

In WITH DOCKER:

test:
    FROM alpine:3.13
    WITH DOCKER --pull ubuntu:latest
        RUN --interactive type=ephemeral docker run -it ubuntu:latest /bin/sh -c 'apt update && apt install -y elixir && iex'
    END

In a --push:

test:
    FROM alpine:3.13
    RUN --push --interactive type=save ash

Of note, ephemeral sessions are evaluated at the end; much like Images and Artifacts. This is to avoid logging interruptions, and avoid other parallelization issues (see the new InteractiveSession struct and its similarities to Save(Image/Artifact). Saved sessions are evaluated inline and do not suffer from this issue.

Invalid, but tempting things you may attempt:

• Use within a LOCALLY. Just open an new shell, why would you do this?
• Multiple --interactive sessions within a single invocation
  • Includes creating an IF-like statement by hiding one in a --push
• Any statements after an --interactive
  • Includes FROM -ing a target with an --interactive
• Usage without a type arg. This is because I can't "undo" parsing the next token as part of the interactive sessions arguments; which lead to weird syntax (--interactive --) or accidentally stealing the first part of the command.
  • Alternative 1: Two args, --interactive-save / --interactive-ephemeral that bake this into the arg itself
  • Alternative 2: Two args, but one only modifies the first. --interactive and --omit to instruct it to ignore the state
  • Alternative 3: Interactive becomes a RUN-like full command; and has options --save or --omit (default)
• Usage when --strict is present or implied.

Later Ideas:

• Remove the single, and last restrictions. I tried to code this so it would more-or-less be code removal only to provide this.
• Use the NewContainer buildkit API. This would require an equal, but different set of hacks.
• Find a way to let builds run in the background without interrupting the flow of the interactive session.
• Distribute an interactive Zork container.

Things Left To Do:

• Documentation
• Some kind of integration test (this could get weird)

[dchw]

This check was needed because we wouldn't otherwise fail on this case, since the FROM that should fail is technically already evaluated:

test:
    FROM alpine:3.13
    RUN apk add bash
    RUN --interactive type=ephemeral bash

from-interactive:
    FROM +test

[vladaionescu]

This looks great!

The only comment I have is regarding that type switch. It feels very wordy for the user to remember. I would go with your first alternative, but have one as "the default".

Alternative 1: Two args, --interactive-save / --interactive-ephemeral that bake this into the arg itself

I would do --interactive (this is the ephemeral one) and --interactive-keep (save has a somewhat different meaning in other places of Earthly).

[dchw]

I would do --interactive (this is the ephemeral one) and --interactive-keep (save has a somewhat different meaning in other places of Earthly).

I did this. Plus allowed SAVE IMAGE after an --interactive command to make it worth actually having the keep. Will be sure to note this in the (forthcoming) docs.