[BUG] config should not keep extends in output YAML

[Vanav]

Description

docker compose config follows extends and resolves them, but also keeps extends in resulting file, This looks like a bug, because extends are already expanded and are useless in resulting file.

Also, this breaks the Docker Swarm use case (moby/moby#31101):

# docker compose config > swarm.yml
# docker stack deploy -c swarm.yml

Compose file contains unsupported options:

extends: Support for `extends` is not implemented yet.

This will work correctly in Compose v1, because it doesn't have this bug and in swarm.yml there will be no extends.

Steps To Reproduce

No response

Compose Version

Docker Compose version v2.16.0

Docker Environment

Docker v23.0.1

Anything else?

No response

[glours]

Hello @Vanav

This is a swarm related bug which doesn't follow the Compose Specification and doesn't support the extends attribute
Please report swarm-related issues to docker/cli repository.

[Vanav]

Yes, it doesn't support extends. Good way to remove extends was to use docker compose config, and it works on v1. Why v2 keeps extends in output, after files are already included?

[Vanav]

For example, docker compose config doesn't leave env_file in resulting file, because it loads variables to config file. So, it shouldn't leave extends in resulting file too.