[BUG] Network aliases from multiple docker-compose files do not get merged

[noraab]

Description

I have network aliases for the same service in multiple docker-compose files; In docker-compose (v1) all aliases get merged, in docker compose (v2) only the aliases from additional files are applied.

Steps To Reproduce

docker-compose.yml

version: "3"
services:
  s1:
    image: busybox
    networks:
      default:
        aliases:
          - alias1
    command: ["sleep", "1h"]

  s2:
    image: busybox
    command: ["ping", "alias1"]

docker-compose.override.yml

version: "3"
services:
  s1:
    networks:
      default:
        aliases:
          - alias2

Run docker-compose config with version 1.29.2

services:
  s1:
    command:
    - sleep
    - 1h
    image: busybox
    networks:
      default:
        aliases:
        - alias1
        - alias2
  s2:
    command:
    - ping
    - alias1
    image: busybox
version: '3'

Run docker compose config with version v2.12.2

name: test
services:
  s1:
    command:
    - sleep
    - 1h
    image: busybox
    networks:
      default:
        aliases:
        - alias2
  s2:
    command:
    - ping
    - alias1
    image: busybox
    networks:
      default: null
networks:
  default:
    name: test_default

Compose Version

$ docker compose version
Docker Compose version v2.12.2

$ docker-compose version
docker-compose version 1.29.2, build 5becea4c
docker-py version: 5.0.0
CPython version: 3.7.10
OpenSSL version: OpenSSL 1.1.0l  10 Sep 2019

Docker Environment

$ docker info
Client:
 Context:    default
 Debug Mode: false
 Plugins:
  app: Docker App (Docker Inc., v0.9.1-beta3)
  buildx: Docker Buildx (Docker Inc., v0.9.1-docker)
  compose: Docker Compose (Docker Inc., v2.12.2)
  scan: Docker Scan (Docker Inc., v0.21.0)

Server:
 Containers: 2
  Running: 0
  Paused: 0
  Stopped: 2
 Images: 36
 Server Version: 20.10.21
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 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: 1c90a442489720eec95342e1789ee8a5e1b9536f
 runc version: v1.1.4-0-g5fd4c4d
 init version: de40ad0
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 5.10.102.1-microsoft-standard-WSL2
 Operating System: Ubuntu 20.04 LTS
 OSType: linux
 Architecture: x86_64
 CPUs: 16
 Total Memory: 24.12GiB
 Name: x
 ID: ADI4:WORP:NW7D:5Z5Y:ULNP:TWEA:LSBA:5GDV:G44E:7LCM:SIK3:RBBM
 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

Anything else?

Basically, this is a new issue for a problem, that has been closed without beeing fixed. See #8719

[ndeloof]

Need to remove https://github.com/compose-spec/compose-go/blob/master/loader/merge.go#L333
Not sure why we get this line, this code is inherited from swarm support introduced in docker/cli, maybe just a mistake

[ndeloof]

an explicit test case has been included in compose-go to confirm this (wrong?) expectation. I'll dig into code history to better understand this decision

[strozl]

I also have this issue. when it will be resolved?

[ndeloof]

The whole merge logic has been introduced at once by docker/cli@1872bd8#diff-3656731ab09fddb23d9fe7c01e366ecd80e82d8dce9720f90583a887064f18b9, which makes it hard to understand the reason this special handling for aliases was introduced.

Considering this behavior is not implemented by Compose v1, I guess we can assume we should better adopt backward compatibility, and investigate ability for an override file to unset values (compose-spec/compose-spec#284)

[noraab]

Hi @ndeloof,
thank you very much for providing a fix. I'm sorry to ask, but in which version will the fix be released? I can't find the specific info anywhere.

[ndeloof]

not released yet. Probably in next release v2.14.2. Check the changelog