Allow setting environment variables using the build image

[sambhav]

Signed-off-by: Sambhav Kothari [email protected]

Readable

Reference Implementation

[buildpack-bot]

Maintainers,

As you review this RFC please queue up issues to be created using the following commands:

/queue-issue <repo> "<title>" [labels]...
/unqueue-issue <uid>

Issues

• ✅ 6b8287 - [RFC #0109] Allow setting environment variables using the build image lifecycle#956 "Allow setting environment variables using the build image"
• ✅ 6a0e12 - [RFC #0109] Allow setting environment variables using the build image spec#330 "Allow setting environment variables using the build image"
• ✅ 647b46 - [RFC #0109] Allow setting environment variables using the build image docs#531 "Allow setting environment variables using the build image"

[natalieparellano]

Is it possible to include a buildpack-provided value in this example? If I'm not mistaken, the order of application is:
buildpack -> platform (behavior: override) -> builder (behavior: configurable, with default default)

I recall that changing the order of application would be a larger breaking change - but what about changing the platform behavior so that it is:
buildpack -> platform (behavior: configurable, with default default) -> builder (behavior: configurable, with default default)

Platforms such as pack could add .override to env var filenames, to keep the same behavior. In the case of "special" env vars such as PATH where the contents are always prepended, platforms could add .prepend to env var filenames.

[natalieparellano]

I would be really happy if we could make the behavior of the platform env directory more consistent with the builder env directory. That said, if that is too big of a change to tackle right now, I'm also fine to wait until some later date to improve the env API.

[sambhav]

@natalieparellano the platform directory change seems like something that could be done independently. I am wary of scope creep on this RFC and gathering consensus again on the new set of changes. Would it be okay if we merge this RFC in first (given that we already have a draft PR implemention in lifecycle) and then have another RFC to make platform behaviour more consistent with the rest of the env API?

[natalieparellano]

@samj1912 I am good with that 🙂 ...if there's general consensus that the platform change IS something we'd like to do, I'd be happy to draft the RFC.

[natalieparellano]

Should we move this to "voting" with a close date?

[sambhav]

Moving to voting with a merge date of Nov 10.

[sambhav]

/queue-issue buildpacks/lifecycle "Allow setting environment variables using the build image"
/queue-issue buildpacks/spec "Allow setting environment variables using the build image"
/queue-issue buildpacks/docs "Allow setting environment variables using the build image"