Adds the ability to set a target build stage to a Dockerfile (#4810)

Co-authored-by: Eddú Meléndez <[email protected]>

Author: GenghisChen

core/src/main/java/org/testcontainers/images/builder/ImageFromDockerfile.java

@@ -60,6 +60,8 @@ public class ImageFromDockerfile
 
     private Optional<Path> dockerfile = Optional.empty();
 
+    private Optional<String> target = Optional.empty();
+
     private Set<String> dependencyImageNames = Collections.emptySet();
 
     public ImageFromDockerfile() {
@@ -177,6 +179,7 @@ protected void configure(BuildImageCmd buildImageCmd) {
             });
 
         this.buildArgs.forEach(buildImageCmd::withBuildArg);
+        this.target.ifPresent(buildImageCmd::withTarget);
     }
 
     private void prePullDependencyImages(Set<String> imagesToPull) {
@@ -211,6 +214,16 @@ public ImageFromDockerfile withBuildArgs(final Map<String, String> args) {
         return this;
     }
 
+    /**
+     * Sets the target build stage to use.
+     *
+     * @param target the target build stage
+     */
+    public ImageFromDockerfile withTarget(String target) {
+        this.target = Optional.of(target);
+        return this;
+    }
+
     /**
      * Sets the Dockerfile to be used for this image.
      *

core/src/test/java/org/testcontainers/containers/MultiStageBuildTest.java

@@ -0,0 +1,28 @@
+package org.testcontainers.containers;
+
+import org.junit.Test;
+import org.testcontainers.images.builder.ImageFromDockerfile;
+
+import java.io.IOException;
+import java.nio.file.Paths;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class MultiStageBuildTest {
+
+    @Test
+    public void testDockerMultistageBuild() throws IOException, InterruptedException {
+        try (
+            GenericContainer<?> container = new GenericContainer<>(
+                new ImageFromDockerfile()
+                    .withDockerfile(Paths.get("src/test/resources/Dockerfile-multistage"))
+                    .withTarget("builder")
+            )
+                .withCommand("/bin/sh", "-c", "sleep 10")
+        ) {
+            container.start();
+            assertThat(container.execInContainer("pwd").getStdout()).contains("/my-files");
+            assertThat(container.execInContainer("ls").getStdout()).contains("hello.txt");
+        }
+    }
+}

core/src/test/resources/Dockerfile-multistage

@@ -0,0 +1,9 @@
+FROM alpine:3.14 AS builder
+
+WORKDIR /my-files
+
+RUN echo 'Hello World' > hello.txt
+
+FROM alpine:3.14
+
+COPY --from=builder /my-files/hello.txt hello.txt