Fix gw priority network order

pkg/compose/convergence_test.go

@@ -30,8 +30,10 @@ import (
 	"github.com/docker/docker/api/types/image"
 	"github.com/docker/docker/api/types/network"
 	"github.com/docker/go-connections/nat"
+	"github.com/stretchr/testify/require"
 	"go.uber.org/mock/gomock"
 	"gotest.tools/v3/assert"
+	"gotest.tools/v3/assert/cmp"
 
 	"github.com/docker/compose/v5/pkg/api"
 	"github.com/docker/compose/v5/pkg/mocks"
@@ -425,3 +427,42 @@ func TestCreateMobyContainer(t *testing.T) {
 		assert.NilError(t, err)
 	})
 }
+
+func TestDefaultNetworkSettingsGwPrioritySelectsPrimaryNetwork(t *testing.T) {
+	project := &types.Project{
+		Name: "test",
+		Networks: map[string]types.NetworkConfig{
+			"net1": {Name: "net1"},
+			"net2": {Name: "net2"},
+		},
+	}
+
+	service := types.ServiceConfig{
+		Name: "svc",
+		Networks: map[string]*types.ServiceNetworkConfig{
+			"net1": {GatewayPriority: 0},
+			"net2": {GatewayPriority: 100},
+		},
+	}
+
+	mode, netConfig, err := defaultNetworkSettings(
+		project,
+		service,
+		0,
+		nil,
+		false,
+		APIVersion144,
+	)
+
+	require.NoError(t, err)
+	require.NotNil(t, netConfig)
+
+	endpoints := netConfig.EndpointsConfig
+	require.Len(t, endpoints, 2)
+
+	assert.Assert(t, cmp.Contains(endpoints, "net1"))
+	assert.Assert(t, cmp.Contains(endpoints, "net2"))
+
+	// gw_priority must only affect primary network selection
+	assert.Assert(t, cmp.Equal(container.NetworkMode("net1"), mode))
+}

pkg/compose/create.go

@@ -519,8 +519,17 @@ func defaultNetworkSettings(project *types.Project,
 	} else {
 		primaryNetworkKey = "default"
 	}
+
 	primaryNetworkMobyNetworkName := project.Networks[primaryNetworkKey].Name
-	primaryNetworkEndpoint := createEndpointSettings(project, service, serviceIndex, primaryNetworkKey, links, useNetworkAliases)
+	primaryNetworkEndpoint := createEndpointSettings(
+		project,
+		service,
+		serviceIndex,
+		primaryNetworkKey,
+		links,
+		useNetworkAliases,
+	)
+
 	endpointsConfig := map[string]*network.EndpointSettings{}
 
 	// Starting from API version 1.44, the Engine will take several EndpointsConfigs
@@ -532,7 +541,14 @@ func defaultNetworkSettings(project *types.Project,
 			serviceNetworks := service.NetworksByPriority()
 			for _, networkKey := range serviceNetworks[1:] {
 				mobyNetworkName := project.Networks[networkKey].Name
-				epSettings := createEndpointSettings(project, service, serviceIndex, networkKey, links, useNetworkAliases)
+				epSettings := createEndpointSettings(
+					project,
+					service,
+					serviceIndex,
+					networkKey,
+					links,
+					useNetworkAliases,
+				)
 				endpointsConfig[mobyNetworkName] = epSettings
 			}
 		}
@@ -544,12 +560,17 @@ func defaultNetworkSettings(project *types.Project,
 	if versions.LessThan(version, APIVersion149) {
 		for _, config := range service.Networks {
 			if config != nil && config.InterfaceName != "" {
-				return "", nil, fmt.Errorf("interface_name requires Docker Engine %s or later", DockerEngineV28_1)
+				return "", nil, fmt.Errorf(
+					"interface_name requires Docker Engine %s or later",
+					DockerEngineV28_1,
+				)
 			}
 		}
 	}
 
+	// Include the primary network
 	endpointsConfig[primaryNetworkMobyNetworkName] = primaryNetworkEndpoint
+
 	networkConfig := &network.NetworkingConfig{
 		EndpointsConfig: endpointsConfig,
 	}