Add LATEST_EXISTING manifest merge strategy

src/main/java/org/wildfly/prospero/extras/manifest/merge/ManifestMergeCommand.java

@@ -48,7 +48,7 @@ public Integer call() throws Exception {
     }
 
     public static ChannelManifest merge(ChannelManifest manifestOne, ChannelManifest manifestTwo,
-                                        VersionMergeStrategy.Strategies mergeStrategy,
+                                        VersionMergeStrategy mergeStrategy,
                                         String mergedManifestName, String mergedManifestId) {
         Objects.requireNonNull(manifestOne);
         Objects.requireNonNull(manifestTwo);
@@ -62,14 +62,25 @@ public static ChannelManifest merge(ChannelManifest manifestOne, ChannelManifest
         Set<Stream> merged = new TreeSet<>(streamsOne);
         for (Stream s : streamsTwo) {
             final String key = s.getGroupId() + ":" + s.getArtifactId();
+            final String versionOne;
+            final String versionTwo = s.getVersion();
             if (!presentKeys.containsKey(key)) {
-                merged.add(s);
+                versionOne = null;
             } else {
-                final String version = mergeStrategy.merge(presentKeys.get(key).getVersion(), s.getVersion());
-                if (!version.equals(presentKeys.get(key).getVersion())) {
+                versionOne = presentKeys.get(key).getVersion();
+            }
+
+            final String version = mergeStrategy.merge(versionOne, versionTwo);
+            final Stream streamOne = presentKeys.get(key);
+            if (version == null) {
+                if (streamOne != null) {
+                    merged.remove(streamOne);
+                }
+            } else if (!version.equals(versionOne)) {
+                if (streamOne != null) {
                     merged.remove(presentKeys.get(key));
-                    merged.add(s);
                 }
+                merged.add(s);
             }
         }
 

src/main/java/org/wildfly/prospero/extras/manifest/merge/VersionMergeStrategy.java

@@ -5,7 +5,8 @@
 public interface VersionMergeStrategy {
     enum Strategies implements VersionMergeStrategy {
         LATEST(new LatestMergeStrategy()),
-        FIRST(new FirstMergeStrategy());
+        FIRST(new FirstMergeStrategy()),
+        LATEST_EXISTING(new LatestExistingMergeStrategy());
 
         private final VersionMergeStrategy mergeStrategy;
 
@@ -24,18 +25,31 @@ class FirstMergeStrategy implements VersionMergeStrategy {
 
     @Override
     public String merge(String v1, String v2) {
-        return v1;
+        return v1 == null ? v2 : v1;
     }
 }
 
 class LatestMergeStrategy implements VersionMergeStrategy {
 
     @Override
     public String merge(String v1, String v2) {
+        if (v1 == null || v2 == null) {
+            return v1 == null ? v2 : v1;
+        }
         if (VersionMatcher.COMPARATOR.compare(v2, v1) > 0) {
             return v2;
         } else {
             return v1;
         }
     }
 }
+
+class LatestExistingMergeStrategy extends LatestMergeStrategy {
+    @Override
+    public String merge(String v1, String v2) {
+        if (v1 == null) {
+            return null;
+        }
+        return super.merge(v1, v2);
+    }
+}

src/test/java/org/wildfly/prospero/extras/manifest/merge/ManifestMergeCommandTest.java

@@ -0,0 +1,48 @@
+package org.wildfly.prospero.extras.manifest.merge;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+import org.wildfly.channel.ChannelManifest;
+import org.wildfly.channel.Stream;
+
+class ManifestMergeCommandTest {
+
+    protected static final ChannelManifest MANIFEST_ONE = new ChannelManifest(null, null, null, List.of(new Stream("org.test", "test-one", "1.0.0")));
+    protected static final ChannelManifest MANIFEST_TWO = new ChannelManifest(null, null, null, List.of(new Stream("org.test", "test-one", "1.1.0")));
+
+    @Test
+    public void pickFirstVersion() throws Exception {
+
+
+        final VersionMergeStrategy strategy = (v1, v2) -> v1;
+        final ChannelManifest merged = ManifestMergeCommand.merge(MANIFEST_ONE, MANIFEST_TWO, strategy, null, null);
+
+        assertThat(merged.getStreams())
+                .containsOnly(new Stream("org.test", "test-one", "1.0.0"));
+
+    }
+
+    @Test
+    public void pickSecondVersion() throws Exception {
+        final VersionMergeStrategy strategy = (v1, v2) -> v2;
+        final ChannelManifest merged = ManifestMergeCommand.merge(MANIFEST_ONE, MANIFEST_TWO, strategy, null, null);
+
+        assertThat(merged.getStreams())
+                .containsOnly(new Stream("org.test", "test-one", "1.1.0"));
+
+    }
+
+    @Test
+    public void rejectStream() throws Exception {
+        // if the strategy returns null, the stream should be removed
+        final VersionMergeStrategy strategy = (v1, v2) -> null;
+        final ChannelManifest merged = ManifestMergeCommand.merge(MANIFEST_ONE, MANIFEST_TWO, strategy, null, null);
+
+        assertThat(merged.getStreams())
+                .isEmpty();
+
+    }
+}

src/test/java/org/wildfly/prospero/extras/manifest/merge/VersionMergeStrategyTest.java

@@ -11,12 +11,25 @@ public void testLatestVersionMerge() {
         final VersionMergeStrategy latest = new LatestMergeStrategy();
         assertEquals("1.2.4", latest.merge("1.2.3", "1.2.4"));
         assertEquals("1.2.4", latest.merge("1.2.4", "1.2.3"));
+        assertEquals("1.2.4", latest.merge("1.2.4", null));
+        assertEquals("1.2.4", latest.merge(null, "1.2.4"));
     }
 
     @Test
     public void testFirstVersionMerge() {
         final VersionMergeStrategy first = new FirstMergeStrategy();
         assertEquals("1.2.3", first.merge("1.2.3", "1.2.4"));
         assertEquals("1.2.4", first.merge("1.2.4", "1.2.3"));
+        assertEquals("1.2.4", first.merge("1.2.4", null));
+        assertEquals("1.2.4", first.merge(null, "1.2.4"));
+    }
+
+    @Test
+    public void testLatestExistingVersionMerge() {
+        final VersionMergeStrategy strategy = new LatestExistingMergeStrategy();
+        assertEquals("1.2.4", strategy.merge("1.2.3", "1.2.4"));
+        assertEquals("1.2.4", strategy.merge("1.2.4", "1.2.3"));
+        assertEquals("1.2.4", strategy.merge("1.2.4", null));
+        assertNull(strategy.merge(null, "1.2.4"));
     }
 }