[BUG] config --variables lists broken variable names

[jonasgeiler]

Description

I'm not sure whether to report this here or at compose-spec/compose-go.

I came across a strange issue where running docker compose config --variables lists weird and incorrect variable names like so:

NAME                             REQUIRED            DEFAULT VALUE       ALTERNATE VALUE
SUBDOMAIN:-redis}.${ROOTDOMAIN   true

Docker compose seems to wrongly parse the variable interpolations and match the furthest : instead of the closest : for the variable name.
When running docker compose config the variable interpolations work correctly and the way they should, so this is only an issue when listing the variables using --variables.

Steps To Reproduce

1. Create a docker-compose.yml file with the following content:

   services:
     redis:
       image: "redis:alpine"
       domainname: ${SUBDOMAIN:-redis}.${ROOTDOMAIN:?}

2. Run docker compose config --variables
3. This is the output:

   NAME                             REQUIRED            DEFAULT VALUE       ALTERNATE VALUE
   SUBDOMAIN:-redis}.${ROOTDOMAIN   true
   

   And this is the output I would EXPECT:

   NAME                             REQUIRED            DEFAULT VALUE       ALTERNATE VALUE
   SUBDOMAIN                        false               redis
   ROOTDOMAIN                       true
   

Compose Version

Docker Compose version 2.27.0

Docker Environment

Client:
 Version:    26.1.0
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  0.14.0
    Path:     /usr/lib/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  2.27.0
    Path:     /usr/lib/docker/cli-plugins/docker-compose

Server:
 Containers: 1
  Running: 0
  Paused: 0
  Stopped: 1
 Images: 10
 Server Version: 26.1.0
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: local
 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: 83031836b2cf55637d7abf847b17134c51b38e53.m
 runc version:
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.8.7-arch1-2
 Operating System: EndeavourOS
 OSType: linux
 Architecture: x86_64
 CPUs: 4
 Total Memory: 15.39GiB
 Name: jonas-laptop
 ID: 271ff1f7-e709-42c4-a1cf-2659a5547a28
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Username: jonasgeiler
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

Anything else?

No response