User that includes GID should be valid.

[rany2]

Please check the following related issue from a project that depends on this library: containers/podlet#106

In short, this compose file is invalid according to the library:

version: "3.7"
services:
  true:
    image: 'docker.io/busybox'
    command: 'true'
    user: 999:999

When the :999 GID portion is dropped, it works fine. It appears that the current implementation doesn't split : to get the group portion.

[k9withabone]

I'll respond here to both issues. It seems that the Compose Specification doesn't define user well. I found a relevant issue, compose-spec/compose-spec#39, but it's over 4.5 years old with no movement on it... Also, docker compose config accepts any string for user, regardless of whether it's a valid user/group name, which is unhelpful. So I guess I'll just have to go by what the docker-run(1) and podman-run(1) man pages say for --user.

[k9withabone]

My initial plan for implementation is the following:

• Rename UserOrGroup to IdOrName.
• Add a User struct like so:

pub struct User {
    pub user: IdOrName,
    pub group: Option<IdOrName>,
}

• Rename the user_or_group module to user.
• Change the type of the user field in Service to Option<User>.

Unfortunately, this has to be a breaking change.