Should recognize inexplicit defined `default` network

[hiimdoublej-swag]

My compose file is like this, which is not considered valid by this package yet.

version: "3"
services:
  test:
    build: .
    networks:
    - default

The default network here is technically valid, even though it's not defined in a networks section for the compose file , since

1. It is the default network created for the user when using docker compose.
2. Running docker-compose up on the same file doesn't show an error, proving that it is a valid compose file.

I think this is a bug and I've scrambled together a sufficient test, but due to my unfamiliarity with golang I'm not sure where/how would I implement a fix.
Is it as straightforward as just ensure there's a default network available in loader/validate.go:checkConsistency ?

Corresponding test:

func TestValidateInexplicitDefaultNetwork(t *testing.T) {
    project := &types.Project{
        Services: types.Services([]types.ServiceConfig{
            {
                Name:  "myservice",
                Image: "scratch",
                Networks: map[string]*types.ServiceNetworkConfig{
                    "default": {},
                },
            },
        }),
    }
    err := checkConsistency(project)
    assert.NilError(t, err)
}

[Nicolas De loof]

which is not considered valid by this package yet

what makes you think so ?
Docker Compose is the reference implementation for the Compose Specification and relies on compose-go, and as you noticed docker compose up has no issue with such a compose file. You can use docker compose config to confirm the implicit default network is well set.

Commented on docker/buildx#906