From bc03b1762f6fab02985145e70bf6edd97102e2dc Mon Sep 17 00:00:00 2001
From: Konrad Windszus <kwin@apache.org>
Date: Mon, 27 Dec 2021 12:00:09 +0100
Subject: [PATCH] [MNG-7375] prevent potential NPE in Metadata.merge(...)

Add unit tests for merge
---
 .../src/main/mdo/metadata.mdo                 |  2 +-
 .../repository/metadata/MetadataTest.java     | 82 +++++++++++++++++++
 2 files changed, 83 insertions(+), 1 deletion(-)
 create mode 100644 maven-repository-metadata/src/test/java/org/apache/maven/artifact/repository/metadata/MetadataTest.java

diff --git a/maven-repository-metadata/src/main/mdo/metadata.mdo b/maven-repository-metadata/src/main/mdo/metadata.mdo
index a6f5299fa6e1..c998fd3b1894 100644
--- a/maven-repository-metadata/src/main/mdo/metadata.mdo
+++ b/maven-repository-metadata/src/main/mdo/metadata.mdo
@@ -97,7 +97,7 @@ under the License.
 
             for ( Plugin preExisting : getPlugins() )
             {
-                if ( preExisting.getPrefix().equals( plugin.getPrefix() ) )
+                if ( java.util.Objects.equals( preExisting.getPrefix(), plugin.getPrefix() ) )
                 {
                     found = true;
                     break;
diff --git a/maven-repository-metadata/src/test/java/org/apache/maven/artifact/repository/metadata/MetadataTest.java b/maven-repository-metadata/src/test/java/org/apache/maven/artifact/repository/metadata/MetadataTest.java
new file mode 100644
index 000000000000..692a178bf139
--- /dev/null
+++ b/maven-repository-metadata/src/test/java/org/apache/maven/artifact/repository/metadata/MetadataTest.java
@@ -0,0 +1,82 @@
+package org.apache.maven.artifact.repository.metadata;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class MetadataTest {
+
+    @Test
+    void testMergeWithEmptyMetadata() {
+        Metadata metadata = new Metadata();
+        
+        Metadata newMetadata = new Metadata();
+        Assertions.assertFalse(metadata.merge(newMetadata));
+    }
+
+    @Test
+    void testMergeWithDifferentPrefixes() {
+        Metadata metadata = new Metadata();
+        Plugin plugin = new Plugin();
+        plugin.setArtifactId("myArtifactId");
+        plugin.setName("My Name");
+        plugin.setPrefix("myprefix");
+        metadata.addPlugin(plugin);
+        
+        Metadata newMetadata = new Metadata();
+        Plugin newPlugin = plugin.clone();
+        newPlugin.setArtifactId("myNewArtifactId");
+        plugin.setPrefix("mynewprefix");
+        newMetadata.addPlugin(newPlugin);
+        Assertions.assertTrue(metadata.merge(newMetadata));
+    }
+
+    @Test
+    void testMergeWithSamePrefixAndDifferentArtifactIds() {
+        Metadata metadata = new Metadata();
+        Plugin plugin = new Plugin();
+        plugin.setArtifactId("myArtifactId");
+        plugin.setName("My Name");
+        plugin.setPrefix("myprefix");
+        metadata.addPlugin(plugin);
+        
+        Metadata newMetadata = new Metadata();
+        Plugin newPlugin = plugin.clone();
+        newPlugin.setArtifactId("myNewArtifactId");
+        newMetadata.addPlugin(newPlugin);
+        Assertions.assertFalse(metadata.merge(newMetadata));
+    }
+
+    @Test
+    void testMergeWithEmptyPrefix() {
+        Metadata metadata = new Metadata();
+        Plugin plugin = new Plugin();
+        plugin.setArtifactId("myArtifactId");
+        plugin.setName("My Name");
+        metadata.addPlugin(plugin);
+        
+        Metadata newMetadata = new Metadata();
+        Plugin newPlugin = plugin.clone();
+        newPlugin.setPrefix("myprefix");
+        newMetadata.addPlugin(newPlugin);
+        Assertions.assertTrue(metadata.merge(newMetadata));
+    }
+}