[BUG] Configs uid, gid and mode is will not take effect with configs of type file

[meldafrawi]

Description

Trying to set uid, gid, and mode for a config resource of type file is not working

Steps To Reproduce

docker compose file:

name: test

configs:
  test_config:
    file: ./test.json

services:
  test:
    image: ubuntu:latest
    command: ["/bin/bash", "-c", "while true; do : ; done"]
    configs:
      - source: test_config
        target: /test.json
        uid: "33"
        gid: "33"
        mode: 0400

Check test.json file ownership & permissions:
docker compose exec -it test ls -la /test.json

Compose Version

Docker Compose version v2.29.7

Docker Environment

Client: Docker Engine - Community
Version: 27.3.1
Context: default
Debug Mode: false
Plugins:
buildx: Docker Buildx (Docker Inc.)
Version: v0.17.1
Path: /usr/libexec/docker/cli-plugins/docker-buildx
compose: Docker Compose (Docker Inc.)
Version: v2.29.7
Path: /usr/libexec/docker/cli-plugins/docker-compose

Server:
Containers: xxx
Running: xxx
Paused: xxx
Stopped: xxx
Images: xxx
Server Version: 27.3.1
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: 7f7fdf5fed64eb6a7caf99b3e12efcf9d60e311c
runc version: v1.1.14-0-g2c9f560
init version: de40ad0
Security Options:
apparmor
seccomp
Profile: builtin
cgroupns
Kernel Version: 6.8.0-48-generic
Operating System: Ubuntu 22.04.5 LTS
OSType: linux
Architecture: x86_64
CPUs: xxx
Total Memory: xxx GiB
Name: nil
ID: 72f5f66c-04c5-4a36-8416-35d7066b9f0e
Docker Root Dir: /var/lib/docker
Debug Mode: false
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false

WARNING: bridge-nf-call-iptables is disabled
WARNING: bridge-nf-call-ip6tables is disabled

Anything else?

No response

[ndeloof]

This is a known limitation, as we use bind mounts to add config file inside container, and bind mount doesn't allow to override uid/gid/mode as seen by container
See #12251 for discussion to add support for this using an alternative approach

[meldafrawi]

@ndeloof is a change in docs required here?

[ndeloof]

would make sense, feel free to propose some additional notes on https://github.com/docker/docs
But this page is a copy from github.com/compose-spec and as such not specific to Docker Compose, so hardly can have a dedicated section on limitations we have in this area. Anyway, Docker Compose will warn you about unsupported attribute when you run compose up command