- restore ability to use a random container name (#1410)

* - re-enable ability to use a random container name

* changed to %e for an "empty container name" placeholder.

Co-authored-by: Rohan Kumar <rohaan@redhat.com>
Co-authored-by: Roland Huß <roland@ro14nd.de>

src/main/asciidoc/inc/image/_naming.adoc

@@ -41,15 +41,17 @@ When specifying the container name pattern the following placeholders can be use
 | *%a*
 | The `<alias>` of an image which must be set. The alias is set in the top-level image configuration
 
+| *%e*
+| Choose an empty container name, which will let the docker engine chose a random container name automatically. This placeholder must be given as single value to `containerNamePattern` when used.
+
 | *%n*
-| A sanitized version of the imag's short name from which this container is created. "Sanitized" means that any non letter, digit, dot or dash is replaced by an underscore.
+| A sanitized version of the image's short name from which this container is created. "Sanitized" means that any non letter, digit, dot or dash is replaced by an underscore.
 
 | *%t*
 | The build time stamp. This is the timestamp which created during the building of an image and locally cached. A rebuild of the image will update the timestamp.
 
 | *%i*
 | An index which is incremented if a container has already been created. With this parameter it is easily possible to have multiple, similar containers. See the example below for more details.
-
 |===
 
 You can combine the placeholders in any combination and will be resolved during `docker:start`, `docker:stop` and `docker:watch`.

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

@@ -20,7 +20,8 @@
  */
 public class ContainerNamingUtil {
 
-    private static final String INDEX_PLACEHOLDER = "%i";
+    static final String INDEX_PLACEHOLDER = "%i";
+    static final String EMPTY_NAME_PLACEHOLDER = "%e";
 
     public static final String DEFAULT_CONTAINER_NAME_PATTERN = "%n-%i";
 
@@ -35,13 +36,15 @@ public static String formatContainerName(final ImageConfiguration image,
         String containerNamePattern = extractContainerNamePattern(image, defaultContainerNamePattern);
         Set<String> existingContainersNames = extractContainerNames(existingContainers);
 
-        final String partiallyApplied =
-            replacePlaceholders(
-                containerNamePattern,
-                image.getName(),
-                image.getAlias(),
-                buildTimestamp);
+        if (shouldUseEmptyName(containerNamePattern)) {
+            return null;
+        }
 
+        String partiallyApplied = replacePlaceholders(
+                        containerNamePattern,
+                        image.getName(),
+                        image.getAlias(),
+                        buildTimestamp);
 
         if (partiallyApplied.contains(INDEX_PLACEHOLDER)) {
             for (long i = 1; i < Long.MAX_VALUE; i++) {
@@ -70,20 +73,18 @@ public static Collection<Container> getContainersToStop(final ImageConfiguration
 
         String containerNamePattern = extractContainerNamePattern(image, defaultContainerNamePattern);
 
-        // Only special treatment for indexed container names
-        if (!containerNamePattern.contains(INDEX_PLACEHOLDER)) {
+        if (shouldUseEmptyName(containerNamePattern) || !containerNamePattern.contains(INDEX_PLACEHOLDER)) {
             return containers;
         }
 
         final String partiallyApplied =
-            replacePlaceholders(
-                containerNamePattern,
-                image.getName(),
-                image.getAlias(),
-                buildTimestamp);
+                replacePlaceholders(
+                        containerNamePattern,
+                        image.getName(),
+                        image.getAlias(),
+                        buildTimestamp);
 
         return keepOnlyLastIndexedContainer(containers, partiallyApplied);
-
     }
 
     // ========================================================================================================
@@ -155,4 +156,12 @@ private static String extractContainerNamePattern(ImageConfiguration image, Stri
     private static String cleanImageName(final String imageName) {
         return new ImageName(imageName).getSimpleName().replaceAll("[^a-zA-Z0-9_.-]+", "_");
     }
+
+    private static boolean shouldUseEmptyName(String pattern) {
+        if (pattern.contains(EMPTY_NAME_PLACEHOLDER) && !pattern.equals(EMPTY_NAME_PLACEHOLDER)) {
+            throw new IllegalArgumentException("Invalid use of container naming pattern " + EMPTY_NAME_PLACEHOLDER);
+        }
+        return pattern.equals(EMPTY_NAME_PLACEHOLDER);
+    }
+
 }

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

@@ -40,6 +40,28 @@ public void testAlias() {
                                 Collections.emptySet()));
     }
 
+    @Test
+    public void testRandom() {
+        Assert.assertEquals(null,
+                ContainerNamingUtil.formatContainerName(
+                    imageConfiguration("jolokia/jolokia_demo","nameAlias", ContainerNamingUtil.EMPTY_NAME_PLACEHOLDER),
+                    null,
+                    new Date(123456),
+                    Collections.emptySet()));
+    }
+
+    @Test
+    public void testMixedRandom() {
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            Assert.assertEquals(null,
+                    ContainerNamingUtil.formatContainerName(
+                        imageConfiguration("jolokia/jolokia_demo","nameAlias", ContainerNamingUtil.EMPTY_NAME_PLACEHOLDER + "-extra"),
+                        null,
+                        new Date(123456),
+                        Collections.emptySet()));
+        });
+    }
+
     @Test
     public void testTimestamp() {
         Assert.assertEquals("123456",
@@ -74,7 +96,7 @@ public void testIndex() {
     public void testAll() {
         Assert.assertEquals("prefix-1-nameAlias-jolokia_demo-123456-postfix",
                             ContainerNamingUtil.formatContainerName(
-                                imageConfiguration("jolokia/jolokia_demo","nameAlias", "prefix-%i-%a-%n-%t-postfix"),
+                                imageConfiguration("jolokia/jolokia_demo","nameAlias", "prefix-" + ContainerNamingUtil.INDEX_PLACEHOLDER + "-%a-%n-%t-postfix"),
                                 null,
                                 new Date(123456),
                                 Collections.emptySet()));