[BUG] depends_on option does not work for extended services

[Yurko-Fedoriv]

Description

I'm trying to understand what has changed over the past few weeks, but earlier, I could define working dependencies in both parent end extending services and they would merge just fine.

Today I returned to working on my project, and depends_on seems to be completely ignored in extended service, both for dependencies defined in parent and child service.

Current behaviour: dependencies do not start with docker compose run service command and docker compose up service for services defined via extends: service: parentService
Expected (previous) behaviour: dependencies defined in depends_on would merge and be accounted for when starting extended service.

Steps To Reproduce

1. Create docker-compose with service hierarchy defined through exends and dependencies defined in depends_on section of either parent or extension service.
2. execute docker compose up service

Compose Version

Docker Compose version v2.32.1

Docker Environment

Client: Docker Engine - Community
 Version:    27.4.1
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.19.3
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.32.1
    Path:     /usr/libexec/docker/cli-plugins/docker-compose

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 0
 Server Version: 27.4.1
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  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 splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 88bf19b2105c8b17560993bee28a01ddc2f97182
 runc version: v1.2.2-0-g7cb3632
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.8.0-51-generic
 Operating System: Ubuntu 24.04.1 LTS
 OSType: linux
 Architecture: x86_64
 CPUs: 8
 Total Memory: 46.61GiB
 Name: yurko-nuc
 ID: 540e3a0f-f2a1-4a5d-b1f2-4aa453b410a9
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

Anything else?

No response

[Yurko-Fedoriv]

In https://docs.docker.com/compose/how-tos/multiple-compose-files/extends/#exceptions-and-limitations I read that depends_on from parent service is not meant to be propagated to the extension service.

Point 1: it used to work just a few weeks ago
Point 2: dependencies defined in the final service are also ignored.

[Yurko-Fedoriv]

Forced version: Docker Compose version v2.31.0

The desired behavior is working correctly in this version

[ndeloof]

Point 1: as you already identified, this was actually a bug with spec not being correctly implemented
Point 2: fixed by compose-spec/compose-go#721

[ndeloof]

see compose-spec/compose-spec#554