feat: Consume image asset metadata from CDK synth

[mildaniel]

Which issue(s) does this change fix?

Why is this change necessary?

How does it address the issue?

What side effects does this change have?

Checklist

• Add input/output type hints to new functions/methods
• Write design document (Do I need to write a design document?)
• Write unit tests
• Write/update functional tests
• Write/update integration tests
• make pr passes
• make update-reproducible-reqs if dependencies were changed
• Write documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jfuss]

Can we add integration tests for this, so we know how this behaves on Windows and Linux systems?

[mildaniel]

Can we add integration tests for this, so we know how this behaves on Windows and Linux systems?

We have an upcoming task for next sprint to add integration testing for all CDK-based build and local commands so I was deferring it until then. We don't currently have the underlying configurations in the develop branch to add integration tests with CDK.

[jfuss]

We have an upcoming task for next sprint to add integration testing for all CDK-based build and local commands so I was deferring it until then. We don't currently have the underlying configurations in the develop branch to add integration tests with CDK.

I don't understand why we are doing this. We can write integ tests now and assume the template format. We do this already but the same thing: https://github.com/aws/aws-sam-cli/blob/develop/tests/integration/local/invoke/test_integrations_cli.py#L67

I don't mean to be a strict here but I am not inclined to approve a pr without proper testing. We shouldn't be splitting testing from the implementation. We wouldn't accept this from contributors, why would we accept it for maintainers?

[mildaniel]

@jfuss That's a completely fair call-out, I will add some integration testing.

I don't understand why we are doing this. We can write integ tests now and assume the template format.

When writing this I was under the assumption that CDK integration tests would start from a CDK app -> cdk synth -> test CFN output. I see that we decided to go with testing starting from the CFN template which won't need some of the changes that would otherwise be required.

[jfuss]

Just a couple small comments. Thanks for adding integ tests to this pr.

[jfuss]

Thanks for handling feedback and adding comments to make the code more readable!