omit IPAM driver if set to "default"

compose.go

@@ -751,7 +751,10 @@ func (g *Generator) buildNixNetworks(composeProject *types.Project) ([]*NixNetwo
 		// https://docs.docker.com/compose/compose-file/06-networks/#ipam
 		// https://docs.docker.com/reference/cli/docker/network/create/
 		// https://docs.podman.io/en/latest/markdown/podman-network-create.1.html
-		if network.Ipam.Driver != "" {
+
+		// If driver is set to "default", we'll omit it and fallback to the
+		// runtime.
+		if network.Ipam.Driver != "" && network.Ipam.Driver != "default" {
 			n.IpamDriver = network.Ipam.Driver
 		}
 		for _, ipamConfig := range network.Ipam.Config {

testdata/TestNetworkSettings.compose.yml

@@ -8,3 +8,6 @@ networks:
   other:
     ipam:
       driver: dhcp
+  default:
+    ipam:
+      driver: default

testdata/TestNetworkSettings.docker.nix

@@ -9,6 +9,19 @@
   virtualisation.oci-containers.backend = "docker";
 
   # Networks
+  systemd.services."docker-network-test_default" = {
+    path = [ pkgs.docker ];
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = true;
+      ExecStop = "docker network rm -f test_default";
+    };
+    script = ''
+      docker network inspect test_default || docker network create test_default
+    '';
+    partOf = [ "docker-compose-test-root.target" ];
+    wantedBy = [ "docker-compose-test-root.target" ];
+  };
   systemd.services."docker-network-test_nginx_net" = {
     path = [ pkgs.docker ];
     serviceConfig = {

testdata/TestNetworkSettings.podman.nix

@@ -14,6 +14,19 @@
   virtualisation.oci-containers.backend = "podman";
 
   # Networks
+  systemd.services."podman-network-test_default" = {
+    path = [ pkgs.podman ];
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = true;
+      ExecStop = "podman network rm -f test_default";
+    };
+    script = ''
+      podman network inspect test_default || podman network create test_default
+    '';
+    partOf = [ "podman-compose-test-root.target" ];
+    wantedBy = [ "podman-compose-test-root.target" ];
+  };
   systemd.services."podman-network-test_nginx_net" = {
     path = [ pkgs.podman ];
     serviceConfig = {