Broken environment variables substitution in command: directive after v2.8.0

[metajiji]

Description

Steps to reproduce the issue:

1. Create docker-compose.yml with variable substitution in command: directive

   version: "3"
   services:
     test:
       image: busybox
       command: >-
         --bar=${BAR:-default}

2. Run docker-compose config or docker-compose up

Describe the results you received:

Wrong result docker-compose config for v2.8.0 version

$ BAR=test docker-compose_v2.8.0 config
name: test
services:
  test:
    command:
    - --bar=default
    image: busybox
    networks:
      default: null
networks:
  default:
    name: test-default

Variable substitution is ignored for

        command: >-
          --bar=${BAR:-default}

Describe the results you expected:

Right result docker-compose config for v2.7.0 version

$ BAR=test docker-compose_v2.7.0 config
name: test
services:
  test:
    command:
    - --bar=test
    image: busybox
    networks:
      default: null
networks:
  default:
    name: test_default

Additional information you deem important (e.g. issue happens only occasionally):

Output of docker compose version:

Docker Compose version v2.8.0

Output of docker info:

Client:
 Context:    default
 Debug Mode: false

Server:
 Containers: 5
  Running: 4
  Paused: 0
  Stopped: 1
 Images: 5
 Server Version: 20.10.10
 Storage Driver: overlay2
  Backing Filesystem: xfs
  Supports d_type: true
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 5b46e404f6b9f661a205e28d59c982d3634148f8
 runc version: v1.0.2-0-g52b36a2d
 init version: de40ad0
 Security Options:
  seccomp
   Profile: default
  cgroupns
 Kernel Version: 5.17.5-300.fc36.x86_64
 Operating System: Fedora Linux 36 (Server Edition)
 OSType: linux
 Architecture: x86_64
 CPUs: 1
 Total Memory: 1.925GiB
 Name: wg-nl
 ID: 3BQL:OSW6:LZI2:ADGC:V3BI:RNIP:YH7O:IDXH:PBLI:GAPX:GZNB:A7PL
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false
 Product License: Community Engine

Additional environment details:

[ulyssessouza]

Hello @metajiji. A fix for that issue is already on going. We should release a patch version ASAP.