feat: can now resolves args from all stages

[JordanGoasdoue]

Fixes #747

Description

feat: can now resolves args from all stages

Submitter Checklist

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• Includes unit tests
• Adds integration tests if needed.

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Reviewer Notes

• The code flow looks good.
• Unit tests and or integration tests added.

Release Notes

Kaniko now resolves args from all stages

[JordanGoasdoue]

@tejal29 I'm stuck here with this error on Travis CI :
https://travis-ci.org/github/GoogleContainerTools/kaniko/jobs/667502659?utm_medium=notification&utm_source=github status

+sudo minikube start --vm-driver=none
* minikube v1.9.0 on Ubuntu 18.04
* Using the none driver based on user configuration
X The none driver requires conntrack to be installed for kubernetes version 1.18.0
Makefile:62: recipe for target 'minikube-setup' failed
make: *** [minikube-setup] Error 78

[JordanGoasdoue]

Something else to add @tejal29 :

Taking this Dockerfile :

ARG IMAGE="ubuntu:16.04"
ARG LAST_STAGE_VARIANT
FROM ${IMAGE} as base
RUN echo hi > /hi
FROM base AS base-dev
RUN echo dev >> /hi
FROM base AS base-prod
RUN echo prod >> /hi
FROM base-${LAST_STAGE_VARIANT}
RUN cat /hi

Using Docker

docker build . -t test-build-arg --build-arg IMAGE --build-arg LAST_STAGE_VARIANT=dev

Will use MetaArg ubuntu:16.04 for ARG IMAGE and :

docker build . -t test-build-arg --build-arg IMAGE="" --build-arg LAST_STAGE_VARIANT=dev

Will return error because ARG IMAGE shouldn't be blank

On Kaniko even :

docker run -v path/to/build:/build localhost:5000/executor-arg:latest --context=/build --no-push --build-arg IMAGE --build-arg LAST_STAGE_VARIANT="dev"

or

docker run -v path/to/build:/build localhost:5000/executor-arg:latest --context=/build --no-push --build-arg IMAGE="" --build-arg LAST_STAGE_VARIANT="dev"

Will use MetaArg ubuntu:16.04 for ARG IMAGE

I didn't find a way to do something 100% similar because
--build-arg IMAGE="" and --build-arg IMAGE react similarely on opts.BuildArgs by adding on it IMAGE=

Here it would be good if opts.BuildArgs wouldn't take IMAGE= on the case we are on --build-arg IMAGE scenario. But it could continue to do so on the case we are on --build-arg IMAGE="" scenario

This way i can then remove the check of empty string on opts.BuildArgs I did here : https://github.com/GoogleContainerTools/kaniko/pull/1160/files#diff-b651d79bcb38f3023c41dfb9e42f6236R108 , and it should work same way than Docker.

What do you think ?

[tejal29]

@JordanGoasdoue Looks like there was a new minikube release yesterday. I will either pin the minikube version to 1.18 or wait for minikube team to suggest

[tejal29]

@JordanGoasdoue Can you please rebase from master.

[tejal29]

Something else to add @tejal29 :

Taking this Dockerfile :

ARG IMAGE="ubuntu:16.04"
ARG LAST_STAGE_VARIANT
FROM ${IMAGE} as base
RUN echo hi > /hi
FROM base AS base-dev
RUN echo dev >> /hi
FROM base AS base-prod
RUN echo prod >> /hi
FROM base-${LAST_STAGE_VARIANT}
RUN cat /hi

Using Docker

docker build . -t test-build-arg --build-arg IMAGE --build-arg LAST_STAGE_VARIANT=dev

Will use MetaArg ubuntu:16.04 for ARG IMAGE and :

docker build . -t test-build-arg --build-arg IMAGE="" --build-arg LAST_STAGE_VARIANT=dev

Will return error because ARG IMAGE shouldn't be blank

On Kaniko even :

docker run -v path/to/build:/build localhost:5000/executor-arg:latest --context=/build --no-push --build-arg IMAGE --build-arg LAST_STAGE_VARIANT="dev"

or

docker run -v path/to/build:/build localhost:5000/executor-arg:latest --context=/build --no-push --build-arg IMAGE="" --build-arg LAST_STAGE_VARIANT="dev"

Will use MetaArg ubuntu:16.04 for ARG IMAGE

I didn't find a way to do something 100% similar because
--build-arg IMAGE="" and --build-arg IMAGE react similarely on opts.BuildArgs by adding on it IMAGE=

Here it would be good if opts.BuildArgs wouldn't take IMAGE= on the case we are on --build-arg IMAGE scenario. But it could continue to do so on the case we are on --build-arg IMAGE="" scenario

This way i can then remove the check of empty string on opts.BuildArgs I did here : https://github.com/GoogleContainerTools/kaniko/pull/1160/files#diff-b651d79bcb38f3023c41dfb9e42f6236R108 , and it should work same way than Docker.

What do you think ?

Sure, we can. But my big worry is we have always supported empty args for a while now and removing that might cause a backward incompatible change for existing users which use this ""

Before doing that, we need to take appropriate steps like

1. First print a warning in N-1 release
2. then follow up with release to change it to an error.

Since no one has yet complained about this i am ok to not address in this PR.
But for sure, in future, i could see ppl wanting to plum their docker build command as is and expect the same result. However, if you are keen, we could definitely add this in incremental steps.

[tejal29]

The PR passes here https://travis-ci.org/github/GoogleContainerTools/kaniko/builds/667817048?utm_medium=notification&utm_source=github_status

[JordanGoasdoue]

Yes we could do that, but first we should see impact of such a change on the code, and yes it's definetely not urgent.

[tejal29]

re-opening for travis to pick up this PR.

[gabyx]

Has this been tested with

FROM alpine:latest as base
RUN echo hi > /hi

FROM base AS base-dev
ARG NAME="1234"
RUN echo "dev:: $NAME" >> /hi

FROM base-dev as base-custom
ARG NAME
RUN echo "custom:: $NAME"
RUN cat /hi

Without specifying --build-arg NAME=...
It should work but it does not... $NAME is empty in base-custom