Allow passing image tag to docker build in buildArgs

[Awem]

Expected behavior

On skaffold build the tag of the docker image is immediately printed after Generating tags... and should therefore be available in the buildArgs template of the docker build configuration.

Actual behavior

It is not available.

Information

• Skaffold version: 1.0.0
• Operating system: Linux
• Contents of skaffold.yaml:

apiVersion: skaffold/v1
kind: Config
build:
  artifacts:
  - image: client
    docker:
      buildArgs:
        IMAGE_NAME: '{{.IMAGE_NAME}}'
  local:
    push: true
    useDockerCLI: true

Steps to reproduce the behavior

1. have a Dockerfile with

ARG IMAGE_NAME
ENV IMAGE_NAME ${IMAGE_NAME}
RUN echo "Building image $IMAGE_NAME

2. skaffold build
3. $IMAGE_NAME won't have a value unless you provide some like IMAGE_NAME=name skaffold build

[tejal29]

@Awem, skaffold runs locally and uses the local environment for substituting the variables.
Skaffold docker builder, does not parse the dockerfile to get to variables set in the dockerfile.

Does that make sense?

Please re-open this if you need more information.

[Awem]

Not sure whether we mean the same thing here. The Dockerfile is just for demonstration of a possible build. I do not want Skaffold to parse the Dockerfile. I am only looking for a possibility to use the name of the image (printed by Skaffold after Generating tags... on skaffold build ) in the buildArgs key of my skaffold.yaml.
Since the templating feature is supported for buildArgs this should be easy. The docs say Skaffold allows for certain fields in the config to be templated with values either from environment variables, or certain special values computed by Skaffold. The image name would be such a computed value which is already available at the time the buildArgs are passed.

[balopat]

Thank you for opening - this is a bug, the docs are confusing and the code is terribly inconsistent.

It is supposed to work, as we do evaluate env vars there. However, our calculated values are handled inconsistently across the code base:

ExecuteEnvTemplate takes an extra map where we should pass down the calculated fields.
https://github.com/GoogleContainerTools/skaffold/blob/master/pkg/skaffold/util/env_template.go#L40

As I'm looking at references to this method - a bunch of places (including the docker builder) it is called with nil... this is inconsistent even within helm fields themselves.

The solution will be to have one way of evaluating templates in the code.

[javier-b-perez]

hi,
I have a similar use case, but I only need to pass the tag generated by skaffold.
I'm using SKAFFOLD_DEFAULT_REPO + SKAFFOLD_TAG as my workaround, but this prevent me from using tag generated by skaffold (I need to generate the tag myself, before calling skaffold).

apiVersion: skaffold/v2beta1
kind: Config
build:
  local:
    push: false
  artifacts:
    # Builder images are used to build the other containers.
    # You need to specify the registry you want to use:
    # export SKAFFOLD_DEFAULT_REPO=gcr.io/my-gcp-project
    # export SKAFFOLD_TAG=latest
  - image: gobuilder
    context: build/gobuilder
    docker:
      dockerfile: Dockerfile
  # These containers are using builders + src.
  - image: my-app
    docker:
      dockerfile: my-app/Dockerfile
      buildArgs:
        GOBUILDER: "{{.SKAFFOLD_DEFAULT_REPO}}/gobuilder:{{.SKAFFOLD_TAG}}"

The my-app Dockerfile looks like

ARG GOBUILDER=gcr.io/my-gcp-project/gobuilder:latest
FROM ${GOBUILDER} as builder
...
RUN go build ...

is there a way we can make some skaffold variables available for buildArgs?

[nkubala]

going to close this as a dupe of #3343 since I think it will be addressed if/when we fix that one. trying to keep all the conversations in one place :)

[javier-b-perez]

I don't think that #3343 fixed the issue.
I created a new one #4295 with a repo to reproduce and documented workaround.