Support running Rake tasks during build process about rake

[robdimsdale]

@paketo-buildpacks/ruby-maintainers I'm happy to take a look at implementing this. The proposal above makes sense to me (and would be a PR to the ruby buildpack) but I recognize I might be missing some context.

Any other thoughts before I take a look at implementing this?

[sophiewigmore]

@robdimsdale sounds good to me! I don't think I have anything to add here. I can assign you to the issue

[robdimsdale]

I opened a PR for this over at paketo-buildpacks/ruby#757 - happy to take the discussion there.

[sophiewigmore]

@robdimsdale I might have blanked out a bit when I first said that it would only be a language family change, apologies. This build provides a launch web process, so unless I've misunderstood, I think that this buildpack would need to change to run a command during build, rather than contribute a start command.

[robdimsdale]

No problem! I didn't think it could be that easy!

I'll redirect my attention (and the conversation) back to this buildpack.

It's not immediately obvious to me how to differentiate between running a command as a web launch process (the current behavior) and running commands during the build phase instead. I can do some research, but do you have any ideas off the top of your head?

[sophiewigmore]

I can't think of any buildpacks that do both in a conditional way outlined in this issue. Running a command during the build phase would look more like what the Dotnet Publish CNB does, and running a launch process looks more like what Dotnet Execute CNB does.

[robdimsdale]

Yeah, I think I see two options to achieve this conditional behavior of build-time execution vs launch-time execution.

1. Use an environment variable to instruct this buildpack whether to run during build or create a launch command
2. Create a separate buildpack for running commands during build, and leave this one as launch-only. This is essentially the same thing as the .NET buildpacks you linked to.

Honestly, I don't like either of these solutions. Do you have any other suggestions? cc @paketo-buildpacks/ruby-maintainers

[sophiewigmore]

@robdimsdale I'd be inclined to create a new buildpack so we can have a separation of concerns. It's unfortunate because there's so much overlap between the buildpacks, but the detection criteria would probably get a bit messy, and the build phase would have to return two separate results.

[sophiewigmore]

Kashyap filed this issue a while ago, but it's unclear if he did so because he had heard of interest in this feature, or if it was just an idea. It may not even be worth supporting unless it's something folks want, which AFAIK we haven't

[robdimsdale]

Yeah, I'm not super keen on the idea of creating a new buildpack unless there's a clear need. Ruby already has a lot of buildpacks. Do you know if we've heard of any additional requests for this feature?

If we don't have a lot of feedback suggesting this is valuable, I would propose closing this issue without implementing it, as the complexity and maintenance burden is non-trivial.

[ryanmoran]

If we don't have a lot of feedback suggesting this is valuable, I would propose closing this issue without implementing it, as the complexity and maintenance burden is non-trivial.

I'm onboard with this idea.