Volume definition required for single use volumes

[fwsmit]

Describe the bug

Podman-compose always requires volume labels to be defined in the top-level config, otherwise it will stop and give the error RuntimeError: volume [volume_name] not defined in top level. This is wrong, since the spec says this is not needed for volumes that are used in a single service:

If the mount is a host path and is only used by a single service, it can be declared as part of the service definition. To reuse a volume across multiple services, a named volume must be declared in the [top-level volumes key](https://github.com/compose-spec/compose-spec/blob/master/07-volumes.md).

To Reproduce Steps to reproduce the behavior:

1. Try to run a docker-compose.yml with volume labels such as the following:

services:
  frontend:
    image: busybox
    volumes:
      - testdir:/home/user:z

Expected behavior It runs

Actual behavior It gives the error RuntimeError: volume [testdir] not defined in top level. Adding the following fixes the error. But this should not be required.

volumes:
   testdir:

Output

$ podman-compose version
podman-compose version: 1.0.6
['podman', '--version', '']
using podman version: 4.6.1
podman-compose version 1.0.6
podman --version 
podman version 4.6.1
exit code: 0


$ podman-compose up
...
podman-compose version: 1.0.6
['podman', '--version', '']
using podman version: 4.6.1
Traceback (most recent call last):
  File "/usr/bin/podman-compose", line 33, in <module>
    sys.exit(load_entry_point('podman-compose==1.0.6', 'console_scripts', 'podman-compose')())
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/podman_compose.py", line 2940, in main
    podman_compose.run()
  File "/usr/lib/python3.11/site-packages/podman_compose.py", line 1420, in run
    self._parse_compose_file()
  File "/usr/lib/python3.11/site-packages/podman_compose.py", line 1627, in _parse_compose_file
    raise RuntimeError(
RuntimeError: volume [testdir] not defined in top level

Environment:

• OS: Linux
• podman version: 4.6.1
• podman compose version: 1.0.6

Additional context

The bug is introduced in https://github.com/containers/podman-compose/commit/154a51245ff2c5c8c3690d3a0035b710b69d0c3d.

ref: #746

[gbschenkel]

Just found this issue, but I think is to be happen this way.

when you use

volumes:
  abc_data:

services:
  abc:
    volumes:
      - abc_data:/data

You are telling you want a external volume which can be shared with other service. Now if you only want use a directory as volume, you need do:

# volumes:
#   abc_data:

services:
  abc:
    volumes:
      - ./abc_data:/data

You need inform you are using a filesystem structure, using ./ as a directory in the current path, or just use a full path.