I'm thinking this may be a simple error, but nothing I've tried has worked. I'm trying to get my CI workflow on Github working, but I'm having trouble with passing in my build arguments. My

docker_image

target is very simple:

docker_image(
    name="app",
    image_tags=["{build_args.GIT_COMMIT}", "latest"],
    registries=["{build_args.REGISTRY}"],
)

then I have Github run it using

./pants --docker-build-args="[GIT_COMMIT=${GITHUB_SHA::7}, REGISTRY=${{ steps.login-ecr.outputs.registry }}]" package src/services/app/Dockerfile

. The error is in the 🧵, my guess is I have the syntax wrong in my package statement but I can't figure it out.

list values are parsed as python

list

literals

Having REGISTRY= in quotes or out of quotes is giving two different errors. If I don't have it in quotes, the error is as I wrote above (can't parse the list). If I DO have it in quotes however, I get errors that look like

ProcessExecutionFailure: Process 'Building docker image {build_args.REGISTRY}/dandelion:2bf4e5e +1 additional tag.' failed with exit code 125.

stdout:

stderr:

invalid argument "{build_args.REGISTRY}/dandelion:2bf4e5e" for "-t, --tag" flag: invalid reference format

See 'docker build --help'.

cc @curved-television-6568 any ideas?

Uhm… the

registries

field does not support string interpolation as the

image_tags

field does. It’s not super clear, but mentioned in the docs: https://www.pantsbuild.org/v2.12/docs/reference-docker_image#codeimage_tagscode

tag may use placeholders in curly braces to be interpolated. The placeholders are derived from various sources, such as the Dockerfile instructions and build args.

That snippet about placeholders is missing for the registries field, indicating it does not support it. Sorry for the confusion.

So is there any way to define a registry dynamically like this?

Yes, you can setup registries dynamically.. hmm, the trickier part may be how to apply them to your docker image targets, if they shouldn’t be applied to all of them.. ?

Well they can all use them like this, defined at Github action time. So I can have one "dynamic" definition for everything

Great, so just dynamically declare one default registry, and removing the registry field of each target will have them use the default one

Set it in the

pants.toml

you mean? Something like this:

[docker.registries.company-ecr]
address = {build_args.REGISTRY}

Do the curly braces work there?

No, they do not. Would it be ok to setup the default registry from the cmd line each time?

╰─❯ ./pants --docker-registries='{"default":{"address":"foo.bar"}}' package testprojects/src/python/docker:test-example
⠤ 7.76s Building docker image foo.bar/test-example:1.2.5

yeah no reason that can't work, let me give it a shot...

Just found this, trying to do the same thing getting frustrated. Specifically, this would make my life easier:

[docker]
build_args = ["namebase", "aws_account", "aws_region"]

[docker.registries.legacy-prod]
address = "{build_args.aws_account}.dkr.ecr.{build_args.aws_region}.<http://amazonaws.com|amazonaws.com>"
repository = "{build_args.namebase}"

Hi, I was reading up about this and started wondering if this new official blog post would be useful to you https://www.pantsbuild.org/blog/2024/04/27/simple-versioning-with-git-tags

Interesting, I didn't know about

.pants.bootstrap

and it may help for other things 🙂 in this case we have args passed in from terraform. I think in this specific case we still run into the problem that the registry address doesn't interpolate curly-brace values.