Fix moby/moby #37229 allowing to create networks even there are no services attached to it when deploying stacks

[jaswdr]

- What I did
Make docker stack deploy create networks even if there are no services attached to it, so you can create stack files for networks only
- How I did it
Change cli/compose/convert/compose.go to consider the networks map when servicesNetworks lenght is equals 0
- How to verify it
The issue #37229 in moby repo has more information about how to reproduce the error
- Description for the changelog
Support deploy network only stacks

[silvin-lubecki]

nit:

ifnetwork.External.External {
externalNetworks=append(externalNetworks, network.Name)
} else{
result[networkName] =networkCreateOptions(namespace, network)
}

[silvin-lubecki]

Thank you @jaswdr for this PR! The design is ok for me, what do you think of this feature @thaJeztah@vdemeester ?

[thaJeztah]

Design works for me as well; I don't think we stated that a compose file must contain services, so a file that only has networks (or other objects) should work.

I see the second commit doesn't have a signed-off-by, so DCO check is failing @jaswdr could you squash your commits to make the DCO check pass?

[thaJeztah]

We should also have a test added for this 👍

[jaswdr]

of course @thaJeztah, sorry for this, I will correct this now

[jaswdr]

@thaJeztah done

[jaswdr]

test created

[silvin-lubecki]

I think only one NetworkConfig, whatever it is, is enough to test the feature? The test would be then more compact and less redundant.

[jaswdr]

@silvin-lubecki did you mean, add the content of the TestNetworksCreatedWithoutServices into the TestNetworks?

[silvin-lubecki]

No, I meant remove all network configs except one, like named, in this test 😄

[silvin-lubecki]

Something like this should do the job I guess

funcTestNetworksCreatedWithoutServices(t*testing.T) {
namespace:=Namespace{name: "foo"}
serviceNetworks:=map[string]struct{}{}
source:=networkMap{
"named": composetypes.NetworkConfig{
Name: "othername",
},
}
expected:=map[string]types.NetworkCreate{
"named": {
Labels: map[string]string{
LabelNamespace: "foo",
},
},
}
networks, externals:=Networks(namespace, source, serviceNetworks)
assert.DeepEqual(t, expected, networks)
assert.DeepEqual(t, []string{"special"}, externals)
}

WDYT?

[jaswdr]

Agree, I'll change this and remove the unecessary content

[jaswdr]

@silvin-lubecki simplified test 😄

[silvin-lubecki]

Thank you @jaswdr 👍 !
LGTM

[vdemeester]

The problem I can think of with this PR is that it doesn't act the same as docker-compose.
Using a composefile without services (but network) with docker-compose has almost the same behavior as the current docker stack deploy : it won't create any network.

That said I would be in favor of this PR so let me ping @shin-@dnephin and @thaJeztah to have their thoughts on that 👼

[jaswdr]

@vdemeester if I make another PR to compose to handle the same behavior has this one, did you agree it is ok?

[vdemeester]

@jaswdr yes 👼 I wanted to have @shin-@thaJeztah or @dnephin's opinion before suggesting you that though (so that you don't work on something if we don't reach consensus on whether we wanna do that or not).

[thaJeztah]

Yes we should match the behavior in compose as well (also see my earlier comment #1120 (comment))