(@aws-cdk/aws-ecr-assets): DockerImageAsset - support --build-context flag

[BwL1289]

Describe the feature

We use CDK Pipelines to deploy our infrastructure to dev, staging, and prod accounts.

When we are building dockerfiles using DockerImageAssets, if there are any files/directories the dockerfile needs while being built, we currently have to copy them over any files/directories to the directory where the dockerfile is being built. This is cumbersome and error prone.

Docker now supports (since 2022) the ability to specify multiple build contexts via the --build-context flag.

It would be great to add --build-context to the flags supported here.

Here's an example:

from aws_cdk import aws_ecr_assets as ecr_assets

ecr_docker_image_asset = ecr_assets.DockerImageAsset(
            self,
            "EcrDockerImageAsset",
            directory=<dir>,
            file="Dockerfile",
            build_args=<build_args>,
            build_contexts=["example_build_context_1", "example_build_context_2", ...]
)

Then, we can use the following in the dockerfile like so:

COPY --from=example_build_context_1 ...

Use Case

With --build-context now supported, It's unnecessary to copy any additional files/directories into the build context where you are building your image.

Proposed Solution

Support the --build-context flag.

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.158.0

Environment details (OS name and version, etc.)

macOS Sonoma 14.5, AWS CodeBuild

[khushail]

Hi @BwL1289 , thanks for reaching out.

I see this request raised in the past - #3342 but few workaround were suggested - #3342 (comment) as in favor of not implementing this flag. For now, you could use this directory construct prop to mention the path.

However given the context of usage and support, this would be good to have. So I am marking this as P3 which means it won't be immediately addressed by the team but is open for team as well as community contribution.

[BwL1289]

@khushail this is different than #3342, and there's no obvious workaround I can think of.

Docker now supports multiple build contexts through the use of the --build-context flag, which is different than specifying a context like what was discussed in #3342.

Per the article I referenced, here's an example:

Additional build contexts can be defined with a new --build-context [name]=[value] flag. The key component defines the name for your build context and the value can be:

Local directory – e.g. --build-context project2=../path/to/project2/src
Git repository – e.g. --build-context qemu-src=https://github.com/qemu/qemu.git
HTTP URL to a tarball – e.g. --build-context src=https://example.org/releases/src.tar
Docker image – Define with a docker-image:// prefix, e.g. --build-context alpine=docker-image://alpine:3.15

Please let me know if this makes sense.

[BwL1289]

@khushail this doesn't seem that difficult, though buildx is required. Need to add an option for buildContexts (like buildArgs) and link everything up.

I would create a PR but my TS skills are shaky at best. Let me know how I can help.

[khushail]

@BwL1289 , thanks for clarification and volunteering to contribute.

There are many ways for seeking support and help on this request--

1. I have marked this as P3 which means its a good to have feature. We use +1s to help prioritize our work, and are happy to re-evaluate this issue based on community feedback. So upvotes are requested to prioritise the implementation of this FR. You can reach out to the cdk.dev community on Slack to solicit support for reprioritization.
2. Follow the contribution guide to started and reach out to slack community on this as well.
3. Available CDK Youtube tutorial for PR contribution- https://www.youtube.com/watch?v=ZRxDwAvyQGc

hope that would be helpful!