extended env_file capability to in-docker-compose.yml substitutions

[darKoram]

in #799 the tests show the ability to over-ride an 'environment' var with one from a '.env' file which is useful if the container runtime depends on the var. But another use case for docker-compose .env file is to allow ${var} substitutions in other docker-compose arguments. A common example would be

services:
  app:
    image: myapp
    volumes: ${local_path_to_data}:/data
    env_file: 
      - "./.env"

and
.env
local_path_to_data=/home/me/data # for a linux user
# or
local_path_to_data=/Users/me/data # for a mac user

In my testing, this sort of substitution is not yet supported and gives an error
* error decoding 'Volumes[0]': invalid spec: :/data empty section between colons

I would expect the default behavior to be to create a persistent volume named for the rhs of Volumes populated with the data at local_path_to_data specified in the .env file.

[kbroughton]

I have a workaround for this now:
// this gets the .env files stamped into the -out.yml file
docker-compose config -f docker-compose.yml > docker-compose-out.yml
kompose convert -f docker-compose-out.yml

perhaps kompose should be loading based off of docker-compose config output?

[cpcundill]

Same problem for me. The workaround helps @kbroughton but the docker-compose config output changes the version from '2' in the original to '2.0' which isn't supported by kompose

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[vikasgubbi]

If the environment variable file need to be placed in the application config location , what needs to be done

[vikasgubbi]

Correction

If the environment variable file need to be placed in the custom application config location , what needs to be done

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[TonyApuzzo]

/reopen

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[chiqui3d]

I just tried it for the first time and I got this error: I guess it's because of the .env file or env variable?

error decoding 'Volumes[0]': invalid spec: ./app:: empty section between colons

volumes:
      - ./app:${APP_SYMFONY_DIRECTORY}

[ayoubbensakhria]

I had the same issue, here is what I did:
docker-compose version: '3.7' --> doesn't work
docker-compose version: '2' --> it works