Change merge strategy for service volumes

Signed-off-by: Stoica-Marcu Floris-Andrei <floris.sm@gmail.com>

cli/compose/loader/merge.go

@@ -58,6 +58,7 @@ func mergeServices(base, override []types.ServiceConfig) ([]types.ServiceConfig,
 			reflect.TypeOf([]types.ServiceSecretConfig{}):    mergeSlice(toServiceSecretConfigsMap, toServiceSecretConfigsSlice),
 			reflect.TypeOf([]types.ServiceConfigObjConfig{}): mergeSlice(toServiceConfigObjConfigsMap, toSServiceConfigObjConfigsSlice),
 			reflect.TypeOf(&types.UlimitsConfig{}):           mergeUlimitsConfig,
+			reflect.TypeOf([]types.ServiceVolumeConfig{}):    mergeSlice(toServiceVolumeConfigsMap, toServiceVolumeConfigsSlice),
 			reflect.TypeOf(&types.ServiceNetworkConfig{}):    mergeServiceNetworkConfig,
 		},
 	}
@@ -116,6 +117,18 @@ func toServicePortConfigsMap(s interface{}) (map[interface{}]interface{}, error)
 	return m, nil
 }
 
+func toServiceVolumeConfigsMap(s interface{}) (map[interface{}]interface{}, error) {
+	volumes, ok := s.([]types.ServiceVolumeConfig)
+	if !ok {
+		return nil, errors.Errorf("not a serviceVolumeConfig slice: %v", s)
+	}
+	m := map[interface{}]interface{}{}
+	for _, v := range volumes {
+		m[v.Target] = v
+	}
+	return m, nil
+}
+
 func toServiceSecretConfigsSlice(dst reflect.Value, m map[interface{}]interface{}) error {
 	s := []types.ServiceSecretConfig{}
 	for _, v := range m {
@@ -146,6 +159,16 @@ func toServicePortConfigsSlice(dst reflect.Value, m map[interface{}]interface{})
 	return nil
 }
 
+func toServiceVolumeConfigsSlice(dst reflect.Value, m map[interface{}]interface{}) error {
+	s := []types.ServiceVolumeConfig{}
+	for _, v := range m {
+		s = append(s, v.(types.ServiceVolumeConfig))
+	}
+	sort.Slice(s, func(i, j int) bool { return s[i].Target < s[j].Target })
+	dst.Set(reflect.ValueOf(s))
+	return nil
+}
+
 type tomapFn func(s interface{}) (map[interface{}]interface{}, error)
 type writeValueFromMapFn func(reflect.Value, map[interface{}]interface{}) error
 
@@ -211,6 +234,14 @@ func mergeUlimitsConfig(dst, src reflect.Value) error {
 	return nil
 }
 
+//nolint: unparam
+func mergeServiceVolumeConfig(dst, src reflect.Value) error {
+	if dst.Elem().FieldByName("target").String() == src.Elem().FieldByName("target").String() {
+		dst.Set(src.Elem())
+	}
+	return nil
+}
+
 //nolint: unparam
 func mergeServiceNetworkConfig(dst, src reflect.Value) error {
 	if src.Interface() != reflect.Zero(reflect.TypeOf(src.Interface())).Interface() {

cli/compose/loader/merge_test.go

@@ -1017,6 +1017,81 @@ func TestLoadMultipleNetworks(t *testing.T) {
 	}, config)
 }
 
+func TestLoadMultipleServiceVolumes(t *testing.T) {
+	base := map[string]interface{}{
+		"version": "3.7",
+		"services": map[string]interface{}{
+			"foo": map[string]interface{}{
+				"image": "baz",
+				"volumes": []interface{}{
+					map[string]interface{}{
+						"type":   "volume",
+						"source": "sourceVolume",
+						"target": "/var/app",
+					},
+				},
+			},
+		},
+		"volumes": map[string]interface{}{
+			"sourceVolume": map[string]interface{}{},
+		},
+		"networks": map[string]interface{}{},
+		"secrets":  map[string]interface{}{},
+		"configs":  map[string]interface{}{},
+	}
+	override := map[string]interface{}{
+		"version": "3.7",
+		"services": map[string]interface{}{
+			"foo": map[string]interface{}{
+				"image": "baz",
+				"volumes": []interface{}{
+					map[string]interface{}{
+						"type":   "volume",
+						"source": "/local",
+						"target": "/var/app",
+					},
+				},
+			},
+		},
+		"volumes":  map[string]interface{}{},
+		"networks": map[string]interface{}{},
+		"secrets":  map[string]interface{}{},
+		"configs":  map[string]interface{}{},
+	}
+	configDetails := types.ConfigDetails{
+		ConfigFiles: []types.ConfigFile{
+			{Filename: "base.yml", Config: base},
+			{Filename: "override.yml", Config: override},
+		},
+	}
+	config, err := Load(configDetails)
+	assert.NilError(t, err)
+	assert.DeepEqual(t, &types.Config{
+		Filename: "base.yml",
+		Version:  "3.7",
+		Services: []types.ServiceConfig{
+			{
+				Name:        "foo",
+				Image:       "baz",
+				Environment: types.MappingWithEquals{},
+				Volumes: []types.ServiceVolumeConfig{
+					{
+						Type:   "volume",
+						Source: "/local",
+						Target: "/var/app",
+					},
+				},
+			},
+		},
+		Volumes: map[string]types.VolumeConfig{
+			"sourceVolume": {},
+		},
+		Secrets:  map[string]types.SecretConfig{},
+		Configs:  map[string]types.ConfigObjConfig{},
+		Networks: map[string]types.NetworkConfig{},
+	}, config)
+}
+
 func TestMergeUlimitsConfig(t *testing.T) {
 	specials := &specials{
 		m: map[reflect.Type]func(dst, src reflect.Value) error{