Compose: labels ignore environment variables

[jpic]

Given:

services:
  foo:
    environment:
    - BAR=test
    labels:
    - foo=${BAR}

Will results in:

WARNING: The BAR variable is not set. Defaulting to a blank string.

Instead of expected: label foo=test, no warning

[ulyssessouza]

The environment entry in the service refers to passing the BAR variable to the service, not to be used to interpolate in the compose file. For this, the BAR variable has to be present in the shell when running docker-compose, for example:

$ BAR=test docker-compose up

[jpic]

I know, but what's the reason for not implementing this ?