Variable substitution in YAML keys

[mvasin]

Variable substitution works for YAML's array elements and hash values, but does not work for hash keys (see the last line):

version: "3"

services:
  ubuntu:
    image: ubuntu
    volumes:
      - $VOL

volumes:
  ${VOL}:

=>

$ VOL=some_vol docker-compose up
ERROR: The Compose file './docker-compose.yml' is invalid because:
volumes value '${VOL}' does not match any of the regexes: u'^[a-zA-Z0-9._-]+$'

I'm running docker-compose version 1.17.1, build 6d101fb.

[shin-]

That's by design - you can use the search function to see prior discussion of the same issue.

You can use version: '3.4' and the name key for parametrized volume names.

[mvasin]

I've found #3858, sorry for duplicating.

And thanks for the hint with name in version: "3.4"! It worked perfectly.

[samskiter]

Paging @shin- I think I need this feature or a fix for external EFS volumes (see docker-archive/compose-cli#2164 (comment))