Compose spec says that top-level name MUST be exposed for interpolation, but it isn't

[AaronBeaudoin]

Description

According to the Compose spec:

Whenever project name is defined by top-level name or by some custom mechanism, it MUST be exposed for interpolation and environment variable resolution as COMPOSE_PROJECT_NAME

In my compose.yaml file, I want to customize how the project name is formatted in the names of my containers. To accomplish this, I write a compose.yaml file something like this:

name: some_name

services:
  database:
    ...
    container_name: ${COMPOSE_PROJECT_NAME}_database

When I run docker compose up, I get the following:

WARN[0000] The "COMPOSE_PROJECT_NAME" variable is not set. Defaulting to a blank string. 
[+] Running 1/0
 ⠿ Network some_name_default  Created
 ⠋ Container _database.       Creating
Error response from daemon: Invalid container name (_database), only [a-zA-Z0-9][a-zA-Z0-9_.-] are allowed

Steps to reproduce the issue:

1. Make a compose.yaml file in the same manner I did above.
2. Run docker compose up.

Describe the results you received:

Docker tells me that the COMPOSE_PROJECT_NAME variable is not set, but according to the spec my top-level name property should have been used as the value for this variable. Unless I'm not interpreting it correctly.

Describe the results you expected:

The COMPOSE_PROJECT_NAME variable was set to some_name and I get a container called some_name_database.

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

Nothing.

Output of docker compose version:

Docker Compose version v2.5.1

Output of docker info:

Client:
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc., v0.8.2)
  compose: Docker Compose (Docker Inc., v2.5.1)
  sbom: View the packaged-based Software Bill Of Materials (SBOM) for an image (Anchore Inc., 0.6.0)
  scan: Docker Scan (Docker Inc., v0.17.0)

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 22
 Server Version: 20.10.14
 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: 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: 3df54a852345ae127d1fa3092b95168e4a88e2f8
 runc version: v1.0.3-0-gf46b6ba
 init version: de40ad0
 Security Options:
  seccomp
   Profile: default
  cgroupns
 Kernel Version: 5.10.104-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: aarch64
 CPUs: 6
 Total Memory: 3.841GiB
 Name: docker-desktop
 ID: G6YO:B6GF:LZLT:32JR:UCSS:VSMQ:ICNM:F3IP:RMAT:CHT4:NRVI:U56P
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 HTTP Proxy: http.docker.internal:3128
 HTTPS Proxy: http.docker.internal:3128
 No Proxy: hubproxy.docker.internal
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  hubproxy.docker.internal:5000
  127.0.0.0/8
 Live Restore Enabled: false

Additional environment details:

I'm on a macOS with an M1 Mac, although that probably doesn't matter in this case.

[maxcleme]

@AaronBeaudoin

Thanks for reporting this,

COMPOSE_PROJECT_NAME should indeed be available for interpolation.

Labeling this as bug.