[BUG] Loading COMPOSE_FILE from .env-file stopped working

Description

After updating to compose 2.27.1 loading the COMPOSE_FILE from a .env-file doesn't work anymore as expected. The variable is set, but the additional docker-compose files aren't loaded.

Steps To Reproduce

I set up the following compose-files:

docker-compose.yaml

services:
  test:
    image: bash
    volumes:
      - ./test:/test

docker-compose.network.yaml

services:
  test:
    networks:
      - internal
networks:
  internal:

.env

 COMPOSE_FILE=docker-compose.yaml:docker-compose.network.yaml

Then I run the following command:

docker compose --env-file .env config

Which gives me this output:

name: compose-test
services:
test:
image: bash
networks:
  default: null
volumes:
  - type: bind
    source: <pwd>/compose-test/test
    target: /test
    bind:
      create_host_path: true
networks:
default:
name: compose-test_default

As can be seen, the network-compose-file is completly ignored in this scenario.

When I run docker compose --file docker-compose.yaml --file docker-compose.network.yaml config instead, I get the expected output:

name: compose-test
services:
test:
image: bash
networks:
  internal: null
volumes:
  - type: bind
    source: <pwd>/compose-test/test
    target: /test
    bind:
      create_host_path: true
networks:
internal:
name: compose-test_internal

This also applies to other docker compose commands (e.g. up).

Compose Version

Docker Compose version 2.27.1

Docker Environment

No response

Anything else?

No response

docker / compose