fix: arg stated in a FROM clause can reference other args (#1800)

doc/changelog.md

@@ -3,6 +3,7 @@
   - Automatically create parent directories of portPropertyFile path
   - Added support for `platform` attribute of a container in the docker-compose configuration.
   - `docker:push` failed with build `ARG` in `FROM` ([1778](https://github.com/fabric8io/docker-maven-plugin/issues/1778))
+  - `FROM` can reference `ARG` that references other `ARG` ([1800](https://github.com/fabric8io/docker-maven-plugin/issues/1800))
 
 * **0.44.0** (2024-02-17):
   - Add new option "useDefaultExclusion" for build configuration to handle exclusion of hidden files ([1708](https://github.com/fabric8io/docker-maven-plugin/issues/1708))

src/main/java/io/fabric8/maven/docker/util/DockerFileUtil.java

@@ -185,9 +185,12 @@ static String resolveImageTagFromArgs(String imageTagString, Map<String, String>
         String resolvedImageString = imageTagString;
         Set<String> foundArgs = findAllArgs(imageTagString);
         for (String foundArg : foundArgs) {
+            // check if the arg referenced in imageTagString exists in the Dockerfile
             if (args.containsKey(foundArg)) {
-                resolvedImageString = resolvedImageString.replaceFirst(String.format("\\$\\{*%s\\}*", foundArg),
-                        args.get(foundArg));
+                // resolve args that are referenced by this arg
+                String arg = resolveImageTagFromArgs(args.get(foundArg), args);
+                // replace the arg by its value
+                resolvedImageString = resolvedImageString.replaceFirst(String.format("\\$\\{*%s\\}*", foundArg), arg);
             }
         }
         return resolvedImageString;

src/test/java/io/fabric8/maven/docker/util/DockerFileUtilTest.java

@@ -52,6 +52,35 @@ void testSimple() throws Exception {
             toTest, FixedStringSearchInterpolator.create(), Collections.emptyMap()).get(0));
     }
 
+    @Test
+    void testSimpleWithArgs() throws Exception {
+        File toTest = copyToTempDir("Dockerfile_from_simple_with_args");
+        // default arg value
+        Assertions.assertEquals("alpine:latest", DockerFileUtil.extractBaseImages(
+                toTest, FixedStringSearchInterpolator.create(), Collections.emptyMap()).get(0));
+        // given arg value
+        Assertions.assertEquals("alpine:3", DockerFileUtil.extractBaseImages(
+                toTest, FixedStringSearchInterpolator.create(), Collections.singletonMap("VERSION", "3")).get(0));
+    }
+
+    @Test
+    void testSimpleWithChainedArgs() throws Exception {
+        File toTest = copyToTempDir("Dockerfile_from_simple_with_chained_args");
+        // default arg value
+        Assertions.assertEquals("alpine:latest", DockerFileUtil.extractBaseImages(
+                toTest, FixedStringSearchInterpolator.create(), Collections.emptyMap()).get(0));
+        // given arg value
+        Assertions.assertEquals("archlinux:latest", DockerFileUtil.extractBaseImages(
+                toTest, FixedStringSearchInterpolator.create(), Collections.singletonMap("IMAGE_NAME", "archlinux")).get(0));
+        Assertions.assertEquals("alpine:3", DockerFileUtil.extractBaseImages(
+                toTest, FixedStringSearchInterpolator.create(), Collections.singletonMap("IMAGE_TAG", "3")).get(0));
+        Map<String, String> buildArgsFromConfig = new HashMap<>();
+        buildArgsFromConfig.put("IMAGE_NAME", "archlinux");
+        buildArgsFromConfig.put("IMAGE_TAG", "base-devel");
+        Assertions.assertEquals("archlinux:base-devel", DockerFileUtil.extractBaseImages(
+                toTest, FixedStringSearchInterpolator.create(), buildArgsFromConfig).get(0));
+    }
+
     @Test
     void testMultiStage() throws Exception {
         File toTest = copyToTempDir("Dockerfile_multi_stage");

src/test/resources/io/fabric8/maven/docker/util/Dockerfile_from_simple_with_args

@@ -0,0 +1,3 @@
+# Dockerfile with a simple FROM clause with ARG
+ARG VERSION=latest
+FROM alpine:${VERSION}

src/test/resources/io/fabric8/maven/docker/util/Dockerfile_from_simple_with_chained_args

@@ -0,0 +1,5 @@
+# Dockerfile with a simple FROM clause with ARGs
+ARG IMAGE_NAME=alpine
+ARG IMAGE_TAG=latest
+ARG FULL_IMAGE=${IMAGE_NAME}:${IMAGE_TAG}
+FROM ${FULL_IMAGE}