Added support for the --target parameter in the docker build phase

it/buildx-target/pom.xml

@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>io.fabric8.dmp.itests</groupId>
+    <artifactId>dmp-it-parent</artifactId>
+    <version>0.49-SNAPSHOT</version>
+    <relativePath>../pom.xml</relativePath>
+  </parent>
+
+  <artifactId>dmp-it-buildx-target</artifactId>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>io.fabric8</groupId>
+        <artifactId>docker-maven-plugin</artifactId>
+        <configuration>
+          <images>
+            <image>
+              <name>dmp/buildx-target:${project.version}</name>
+              <build>
+                <dockerFile>${project.basedir}/src/main/docker/Dockerfile</dockerFile>
+                <target>base</target>
+                <buildx>
+                  <platforms>
+                    <platform>linux/amd64</platform>
+                    <platform>linux/arm64</platform>
+                  </platforms>
+                </buildx>
+              </build>
+              <run>
+                <wait>
+                  <log>base</log>
+                  <time>5000</time>
+                </wait>
+              </run>
+            </image>
+          </images>
+        </configuration>
+        <executions>
+          <execution>
+            <id>build</id>
+            <goals>
+              <goal>build</goal>
+            </goals>
+            <phase>package</phase>
+          </execution>
+          <execution>
+            <id>integration-test</id>
+            <goals>
+              <goal>start</goal>
+              <goal>stop</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>

it/buildx-target/src/main/docker/Dockerfile

@@ -0,0 +1,6 @@
+FROM alpine AS base
+RUN echo "base" > /stage.txt
+CMD ["sh", "-c", "cat /stage.txt && sleep infinity"]
+
+FROM base AS final
+RUN echo "final" > /stage.txt

it/dockerfile-target/pom.xml

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>io.fabric8.dmp.itests</groupId>
+    <artifactId>dmp-it-parent</artifactId>
+    <version>0.49-SNAPSHOT</version>
+    <relativePath>../pom.xml</relativePath>
+  </parent>
+
+  <artifactId>dmp-it-dockerfile-target</artifactId>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>io.fabric8</groupId>
+        <artifactId>docker-maven-plugin</artifactId>
+        <configuration>
+          <images>
+            <image>
+              <name>dmp/dockerfile-target:${project.version}</name>
+              <build>
+                <dockerFile>${project.basedir}/src/main/docker/Dockerfile</dockerFile>
+                <target>base</target>
+              </build>
+              <run>
+                <wait>
+                  <log>base</log>
+                  <time>5000</time>
+                </wait>
+              </run>
+            </image>
+          </images>
+        </configuration>
+        <executions>
+          <execution>
+            <id>build</id>
+            <goals>
+              <goal>build</goal>
+            </goals>
+            <phase>package</phase>
+          </execution>
+          <execution>
+            <id>integration-test</id>
+            <goals>
+              <goal>start</goal>
+              <goal>stop</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>

it/dockerfile-target/src/main/docker/Dockerfile

@@ -0,0 +1,6 @@
+FROM alpine AS base
+RUN echo "base" > /stage.txt
+CMD ["sh", "-c", "cat /stage.txt && sleep infinity"]
+
+FROM base AS final
+RUN echo "final" > /stage.txt

it/pom.xml

@@ -23,6 +23,7 @@
     <module>builder</module>
     <module>buildx</module>
     <module>buildx-contextdir</module>
+    <module>buildx-target</module>
     <module>buildx-dependencyset</module>
     <module>buildx-dockerfile</module>
     <module>buildx-dockerfile-secret</module>
@@ -31,6 +32,7 @@
     <module>docker-compose</module>
     <module>docker-compose-dependon</module>
     <module>dockerfile</module>
+    <module>dockerfile-target</module>
     <module>dockerfile-base-as-arg</module>
     <module>dockerfile-base-as-arg-buildconfig</module>
     <module>dockerfile-push-build-arg-from</module>

src/main/asciidoc/inc/build/_buildx.adoc

@@ -66,6 +66,8 @@ element defaults to `min` and the `<sbom>` element defaults to `false`.
 For environment variables add a `<env>` element with a list of variables in the form `<secret name>env variable name</secret name>` (whereas the `secret name` can then be referenced in your Dockerfile.
 For files, add a `<files>` component with a list of paths to the files in the form `<secret name>path to file</secret name>`.
 Examples can be found in the https://github.com/kevinleturc/docker-maven-plugin/blob/bd805724111f7744a38d0b67f80f3e2d2a3e46d2/it/buildx-dockerfile-secret/pom.xml#L26[integration tests].
+NOTE: The `--target` option for multi-stage Dockerfiles is configured via the `<target>` element in the parent `<build>` section, not inside `<buildx>`. It applies to both the regular build path and buildx.
+
 |===
 
 .Examples

src/main/asciidoc/inc/build/_configuration.adoc

@@ -132,6 +132,9 @@ a| Scan the archive specified in `dockerArchive` and find the actual repository
 | *skipTag*
 | If set to `true` this plugin won't add any tags to images. Property: `docker.skip.tag`
 
+| *target*
+| Target build stage to build in a multi-stage Dockerfile. Passed as `--target` to `docker build` and `docker buildx build`. Can be overridden with the property `docker.buildTarget`.
+
 | *tags*
 | List of additional `tag` elements with which an image is to be tagged after the build. Whitespace is trimmed from each element and empty elements are ignored.
 

src/main/asciidoc/inc/external/_property_configuration.adoc

@@ -73,6 +73,9 @@ when a `docker.from` or a `docker.fromExt` is set.
 | *docker.build.network*
 | Set the networking mode for the RUN instructions during build
 
+| *docker.buildTarget*
+| Target build stage in a multi-stage Dockerfile. Passed as `--target` to `docker build` and `docker buildx build`.
+
 | *docker.buildArg.VARIABLE*
 | Set a ARG to be available during build of image. *Note*: this is handled separately from external configuration, and is always available. See <<property-buildargs,Build Args>> for more details.
 

src/main/java/io/fabric8/maven/docker/access/BuildOptions.java

@@ -90,6 +90,13 @@ public BuildOptions network(String network) {
         return this;
     }
 
+    public BuildOptions target(String target) {
+        if (target != null && !target.isEmpty()) {
+            options.put("target", target);
+        }
+        return this;
+    }
+
     public Map<String, String> getOptions() {
         return options;
     }

src/main/java/io/fabric8/maven/docker/config/BuildImageConfiguration.java

@@ -199,6 +199,13 @@ public class BuildImageConfiguration implements Serializable {
     @Parameter
     private Map<String,String> buildOptions;
 
+    /**
+     * Target build stage in a multi-stage Dockerfile.
+     * Passed as {@code --target} to {@code docker build} and {@code docker buildx build}.
+     */
+    @Parameter
+    private String target;
+
     //Default file exclusions
     @Parameter
     private Boolean useDefaultExcludes;
@@ -456,6 +463,10 @@ public Map<String, String> getBuildOptions() {
         return buildOptions;
     }
 
+    public String getTarget() {
+        return target;
+    }
+
     public Map<String, String> getCreateImageOptions() {
         return createImageOptions;
     }
@@ -750,6 +761,11 @@ public Builder buildOptions(Map<String,String> buildOptions) {
             return this;
         }
 
+        public Builder target(String target) {
+            config.target = target;
+            return this;
+        }
+
         public Builder createImageOptions(Map<String, String> createImageOptions) {
             config.createImageOptions = createImageOptions;
             return this;

src/main/java/io/fabric8/maven/docker/config/handler/property/ConfigKey.java

@@ -41,6 +41,7 @@ public enum ConfigKey {
     AUTO_REMOVE,
     BIND,
     BUILD_OPTIONS,
+    BUILD_TARGET,
     BUILDX_PLATFORMS("buildx.platforms", ValueCombinePolicy.Merge),
     BUILDX_BUILDERNAME("buildx.builderName"),
     BUILDX_NODENAME("buildx.nodeName"),

src/main/java/io/fabric8/maven/docker/config/handler/property/PropertyConfigHandler.java

@@ -174,6 +174,7 @@ private BuildImageConfiguration extractBuildConfiguration(ImageConfiguration fro
             .tags(valueProvider.getList(TAGS, config.getTags()))
             .maintainer(valueProvider.getString(MAINTAINER, config.getMaintainer()))
             .network(valueProvider.getString(BUILD_NETWORK, config.getNetwork()))
+            .target(valueProvider.getString(BUILD_TARGET, config.getTarget()))
             .workdir(valueProvider.getString(WORKDIR, config.getWorkdir()))
             .skip(valueProvider.getBoolean(SKIP_BUILD, config.getSkip()))
             .skipPush(valueProvider.getBoolean(SKIP_PUSH, config.getSkipPush()))

src/main/java/io/fabric8/maven/docker/service/BuildService.java

@@ -178,6 +178,7 @@ protected void buildImage(ImageConfiguration imageConfig, MojoParameters params,
                         .squash(squash)
                         .cacheFrom(buildConfig.getCacheFrom())
                         .network(buildConfig.getNetwork())
+                        .target(buildConfig.getTarget())
                         .buildArgs(mergedBuildMap);
         String newImageId = doBuildImage(imageName, dockerArchive, opts);
         log.info("%s: Built image %s", imageConfig.getDescription(), newImageId);

src/main/java/io/fabric8/maven/docker/service/BuildXService.java

@@ -204,6 +204,11 @@ protected void buildX(List<String> buildX, String builderName, BuildDirs buildDi
         if (buildXConfiguration.getCacheTo() != null) {
             cmdLine.add("--cache-to=" + buildXConfiguration.getCacheTo());
         }
+
+        if (buildConfiguration.getTarget() != null) {
+            cmdLine.add("--target=" + buildConfiguration.getTarget());
+        }
+
         SecretConfiguration secret = buildXConfiguration.getSecret();
         if (secret != null) {
             if (secret.getEnvs() != null) {

src/test/java/io/fabric8/maven/docker/service/BuildServiceTest.java

@@ -399,6 +399,54 @@ void testBuildArgsFromDifferentSources() throws MojoExecutionException, DockerAc
         }
     }
 
+    @Test
+    void testTargetIsPropagatedToBuildOptions() throws DockerAccessException, MojoExecutionException {
+        // Given
+        BuildImageConfiguration buildConfig = new BuildImageConfiguration.Builder()
+            .target("my-stage")
+            .build();
+
+        imageConfig = new ImageConfiguration.Builder()
+            .name("build-image")
+            .buildConfig(buildConfig)
+            .build();
+
+        BuildService.BuildContext buildContext = new BuildService.BuildContext.Builder()
+            .mojoParameters(mojoParameters)
+            .build();
+        File buildArchive = buildService.buildArchive(imageConfig, buildContext, "");
+
+        // When
+        buildService.buildImage(imageConfig, null, false, false, Collections.emptyMap(), buildArchive);
+
+        // Then
+        Mockito.verify(docker).buildImage(Mockito.any(), Mockito.any(),
+            Mockito.argThat((BuildOptions options) -> "my-stage".equals(options.getOptions().get("target"))));
+    }
+
+    @Test
+    void testTargetAbsentFromBuildOptionsWhenNotConfigured() throws DockerAccessException, MojoExecutionException {
+        // Given
+        BuildImageConfiguration buildConfig = new BuildImageConfiguration.Builder().build();
+
+        imageConfig = new ImageConfiguration.Builder()
+            .name("build-image")
+            .buildConfig(buildConfig)
+            .build();
+
+        BuildService.BuildContext buildContext = new BuildService.BuildContext.Builder()
+            .mojoParameters(mojoParameters)
+            .build();
+        File buildArchive = buildService.buildArchive(imageConfig, buildContext, "");
+
+        // When
+        buildService.buildImage(imageConfig, null, false, false, Collections.emptyMap(), buildArchive);
+
+        // Then
+        Mockito.verify(docker).buildImage(Mockito.any(), Mockito.any(),
+            Mockito.argThat((BuildOptions options) -> !options.getOptions().containsKey("target")));
+    }
+
     private void givenAnImageConfiguration(String cleanup) {
         BuildImageConfiguration buildConfig = new BuildImageConfiguration.Builder()
             .cleanup(cleanup)

src/test/java/io/fabric8/maven/docker/service/BuildXServiceTest.java

@@ -204,6 +204,32 @@ void testBuildXCacheToIsPresentIfProvided() throws Exception {
         verifyBuildXArgumentPresentInExec("--cache-to=cacheToSpec");
     }
 
+    @Test
+    void testBuildXTargetIsNotPresentIfNotProvided() throws Exception {
+
+        //Given
+        buildConfigUsingBuildx(temporaryFolder, (buildX, buildImage) -> {});
+
+        // When
+        buildx.build(projectPaths, imageConfig, configuredRegistry, authConfigList, buildArchive);
+
+        //Then
+        verifyBuildXArgumentNotPresentInExec("--target");
+    }
+
+    @Test
+    void testBuildXTargetIsPresentIfProvided() throws Exception {
+
+        //Given
+        buildConfigUsingBuildx(temporaryFolder, (buildX, buildImage) -> buildImage.target("my-stage"));
+
+        // When
+        buildx.build(projectPaths, imageConfig, configuredRegistry, authConfigList, buildArchive);
+
+        //Then
+        verifyBuildXArgumentPresentInExec("--target=my-stage");
+    }
+
     private void buildConfigUsingBuildx(File temporaryFolder, BiConsumer<BuildXConfiguration.Builder, BuildImageConfiguration.Builder> spec) {
         final BuildXConfiguration.Builder buildXConfigurationBuilder = new BuildXConfiguration.Builder()
                 .dockerStateDir(temporaryFolder.getAbsolutePath())