Adds ability to specify the stage/target of a multistage dockerfile

pkg/kobject/kobject.go

@@ -144,6 +144,7 @@ type ServiceConfig struct {
 	ExposeService                 string             `compose:"kompose.service.expose"`
 	ExposeServicePath             string             `compose:"kompose.service.expose.path"`
 	BuildLabels                   map[string]string  `compose:"build-labels"`
+	BuildTarget                   string             `compose:""`
 	ExposeServiceTLS              string             `compose:"kompose.service.expose.tls-secret"`
 	ExposeServiceIngressClassName string             `compose:"kompose.service.expose.ingress-class-name"`
 	ImagePullSecret               string             `compose:"kompose.image-pull-secret"`

pkg/loader/compose/compose.go

@@ -559,6 +559,7 @@ func dockerComposeToKomposeMapping(composeObject *types.Project) (kobject.Kompos
 			serviceConfig.Dockerfile = composeServiceConfig.Build.Dockerfile
 			serviceConfig.BuildArgs = composeServiceConfig.Build.Args
 			serviceConfig.BuildLabels = composeServiceConfig.Build.Labels
+			serviceConfig.BuildTarget = composeServiceConfig.Build.Target
 		}
 
 		// env

pkg/transformer/utils.go

@@ -396,7 +396,7 @@ func BuildDockerImage(service kobject.ServiceConfig, name string) error {
 	// Use the build struct function to build the image
 	// Build the image!
 	build := docker.Build{Client: *client}
-	err = build.BuildImage(imagePath, imageName, service.Dockerfile, buildargs)
+	err = build.BuildImage(imagePath, imageName, service.Dockerfile, buildargs, service.BuildTarget)
 
 	if err != nil {
 		return err

pkg/utils/docker/build.go

@@ -43,16 +43,16 @@ in order to make building easier.
 
 if the DOCKER_BUILDKIT is '1', then we will use the docker CLI to build the image
 */
-func (c *Build) BuildImage(source string, image string, dockerfile string, buildargs []dockerlib.BuildArg) error {
+func (c *Build) BuildImage(source string, image string, dockerfile string, buildargs []dockerlib.BuildArg, buildTarget string) error {
 	log.Infof("Building image '%s' from directory '%s'", image, path.Base(source))
 
 	outputBuffer := bytes.NewBuffer(nil)
 	var err error
 
 	if usecli, _ := strconv.ParseBool(os.Getenv("DOCKER_BUILDKIT")); usecli {
-		err = buildDockerCli(source, image, dockerfile, buildargs, outputBuffer)
+		err = buildDockerCli(source, image, dockerfile, buildargs, outputBuffer, buildTarget)
 	} else {
-		err = c.buildDockerClient(source, image, dockerfile, buildargs, outputBuffer)
+		err = c.buildDockerClient(source, image, dockerfile, buildargs, outputBuffer, buildTarget)
 	}
 
 	log.Debugf("Image %s build output:\n%s", image, outputBuffer)
@@ -66,7 +66,7 @@ func (c *Build) BuildImage(source string, image string, dockerfile string, build
 	return nil
 }
 
-func (c *Build) buildDockerClient(source string, image string, dockerfile string, buildargs []dockerlib.BuildArg, outputBuffer *bytes.Buffer) error {
+func (c *Build) buildDockerClient(source string, image string, dockerfile string, buildargs []dockerlib.BuildArg, outputBuffer *bytes.Buffer, buildTarget string) error {
 	// Create a temporary file for tarball image packaging
 	tmpFile, err := os.CreateTemp(os.TempDir(), "kompose-image-build-")
 	if err != nil {
@@ -93,13 +93,14 @@ func (c *Build) buildDockerClient(source string, image string, dockerfile string
 		OutputStream: outputBuffer,
 		Dockerfile:   dockerfile,
 		BuildArgs:    buildargs,
+		Target:       buildTarget,
 	}
 
 	// Build it!
 	return c.Client.BuildImage(opts)
 }
 
-func buildDockerCli(source string, image string, dockerfile string, buildargs []dockerlib.BuildArg, outputBuffer *bytes.Buffer) error {
+func buildDockerCli(source string, image string, dockerfile string, buildargs []dockerlib.BuildArg, outputBuffer *bytes.Buffer, buildTarget string) error {
 	args := []string{"build", "-t", image}
 
 	if dockerfile != "" {
@@ -111,6 +112,9 @@ func buildDockerCli(source string, image string, dockerfile string, buildargs []
 	}
 
 	args = append(args, source)
+	if buildTarget != "" {
+		args = append(args, fmt.Sprintf("--target=%s", buildTarget))
+	}
 
 	cmd := exec.Command("docker", args...)
 	cmd.Stdout = outputBuffer