Support bracket notation for IPv6 port mappings

[chris13524]

I think it would be a good idea to support the bracket notation for IPv6 port mappings. That is, you should be able to do this:

ports:
  - "[::1]:80:80"

I'm aware you can simply omit the brackets to do this currently, however I think supporting the bracket notation would be a good idea.

I believe this for several reasons:

• it is standard to use brackets when writing out IPv6 addresses and port numbers
• the docker run command uses this bracket format for port mappings
• applications such as web browsers and curl use brackets
• it is easier to parse with the eyes
• for some (like myself), it is intuitive to write out port mappings using the brackets just to be greeted by this confusing error message:

  ERROR: The Compose file './docker-compose.yml' is invalid because:
  services.nginx.ports contains an invalid type, it should be a number, or an object
  

  I've done this several times and after a few minutes of Googling come across this issue which reminds me.

[jcsirot]

Hello @chris13524
Thank you for your feature suggestion. We are going to investigate the possibility to integrate it in a future release.

[ndeloof]

Actually implemented separately

[ndeloof]

docker/docker-py#2784