Add target to build configuration

[Bit-Doctor]

I've been using the multi-stage builds in order to reduce the number of Dockerfile in my project as well as having the leanest possible images for production.

My current set-up is a main Dockerfile.prod for production that essentially ends up in a FROM scratch running a binary.
I also have another Dockerfile.dev for development that have dev tools and package like linter, test suite, etc.. It also have a CMD that rebuild on change. This Dockerfile.dev is pretty much the same as the build stage of Dockerfile.prod.

While trying to find a way to get rid of Dockerfile.dev I found stop-at-a-specific-build-stage option for docker build cmd.

Unfortunately it looks like that compose doesn't support it yet.

This option would help me reduce again the number of docker related file per project.
It would be possible for me to have a:

• docker-compose.yml for prod

version: "3.4"
services:

  app:
    image: app:prod
    build:
      context: .
      dockerfile: Dockerfile

• docker-compose.override.yml for dev

version: "3.4"
services:

  app:
    image: app:dev
    build:
      context: .
      dockerfile: Dockerfile
      target: build-stage      

[shin-]

It was added in 3.5.

It was added in 3.4, so I'm not sure why you're having issues. What version of Compose are you running, and what error message do you see?

[kinghuang]

@shin- I see the PR at #5011. However's there's no documentation on https://docs.docker.com/compose/compose-file/#build.

[shin-]

Edited my comment above.

@kinghuang Can you report docs issues to http://github.com/docker/docker.github.io ? Thanks!

[kinghuang]

Found a matching issue: docker/docs#6036

[Bit-Doctor]

Since I could not find it in the v3 document ion I assumed it wasn't supported without actually testing it :( my bad.
Since an issue is open on the documentation I think you can close this issue.

[shin-]

No worries 👍

[meysam81]

hey guys, I was following the discussion in here and some other related issues
so here'e my concern, I can specify target under context label, but let's assume that I have pushed my docker image somewhere, and now that I'm thinking of deploying it, there has to be a mechanism that supports something like this:

    image: my-docker-image
    target: a-custom-target

this needs come from the fact that I should specify my target on a multi staged build of an image which no longer needs to be built so that I would use the context

any idea?