Conversion of underscores to hyphens in kpt function image names is confusing

[bgrant0607]

Expected behavior

This runs a function after locally building it:
$ kpt fn eval . --exec "node dist/my_func_run.js"

Then I want to push the function:
export npm_package_kpt_docker_repo_base="${REGISTRY}/${PROJECT}/${REPOSITORY}"
npm run kpt:docker-build -- --tag=latest
npm run kpt:docker-push -- --tag=latest

I would expect this to work:
$ kpt fn eval . --image "${REGISTRY}/${PROJECT}/${REPOSITORY}/my_func:latest"

Actual behavior

$ kpt fn eval . --image "${REGISTRY}/${PROJECT}/${REPOSITORY}/my_func:latest"

Doesn't find the function. The image is named my-func. This shown by the documentation, but it doesn't mention the conversion of underscores to hyphens.

Steps to reproduce the behavior

I followed https://kpt.dev/sdk/ts-guide

cc @justinsb

[sdowell]

It seems this behavior is intentional and is explicitly implemented here:
https://github.com/GoogleContainerTools/kpt-functions-sdk/blob/master/ts/create-kpt-functions/src/utils/validator.ts#L183

What is the preferred resolution of this?
e.g. change the behavior, update the docs, etc

[mengqiy]

If these are the conventions in docker and js, what we should do here is to update our documentation.

[bgrant0607]

It's not inherent to docker. We were able to push container images with names containing underscores side by side with those containing dashes and were able to add them to the Kptfile pipeline and use them successfully.

What does the Go SDK do?

I personally would probably use dashes in function source file names rather than underscores, but the silent, unexplained conversion was surprising.

[mengqiy]

We currently don't do much scaffolding in the Go SDK. So it doesn't have this problem.