[Issue] Docker buildargs does not support interpolation

[crgarcia12]

• [ X ] Make sure you've installed the latest version using instructions in the wiki

Describe the bug
If you have a Static App (like React) and a backend api in ACA, it would be nice if we could take the output of the infra deployment (the url) and pass it as buildArgs in the dockerfile:

For example:

# main.biceps
...
output REACT_APP_BACKEND_URL string = backend.outputs.uri

# azure.yaml - Notice the environment variables!
...
    frontend:
        project: "src/frontend"
        host: containerapp
        language: ts
        dist: build
        docker:
            path: Dockerfile
            buildArgs:
                - REACT_APP_BACKEND_URL=${REACT_APP_BACKEND_URL}

# deploy infra and populate outputs as environment variables
azd provision --environment dev
# utilize environment variables to interpolate the azure.yaml
azd deploy 

[jongio]

@vhvb1989 This should work right?

[vhvb1989]

@vhvb1989 This should work right?

No. build-args don't support references to env values. This is a feature request (which is not that hard). The only thing to consider is security, as you will want to use --secret instead of --build-arg when referencing a secret from the system environment.

[vhvb1989]

@wbreza FYI