[MPH-217] Ensure packaging is always shown in effective-pom output

src/it/projects/effective-pom-packaging/invoker.properties

@@ -0,0 +1,18 @@
+# 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.
+
+invoker.goals = ${project.groupId}:${project.artifactId}:${project.version}:effective-pom

src/it/projects/effective-pom-packaging/pom.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+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.
+-->
+
+<project>
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>org.apache.maven.its.help</groupId>
+  <artifactId>mph-217</artifactId>
+  <version>1.0-SNAPSHOT</version>
+  <!-- no packaging set, should default to "jar" -->
+</project>

src/it/projects/effective-pom-packaging/verify.groovy

@@ -0,0 +1,25 @@
+/*
+ * 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.
+ */
+def buildLog = new File(basedir, 'build.log');
+assert buildLog.exists()
+
+def LS = System.getProperty("line.separator")
+assert buildLog.text.find(
+        '(?s)' +
+        '  <packaging>jar</packaging>') != null

src/main/java/org/apache/maven/plugins/help/EffectivePomMojo.java

@@ -197,6 +197,16 @@ private void writeEffectivePom(MavenProject project, XMLWriter writer) throws Mo
         // This removes the XML declaration written by MavenXpp3Writer
         String effectivePom = prettyFormat(sWriter.toString(), null, true);
 
+        // MavenXpp3Writer omits packaging when it is null or "jar" (the default).
+        // Ensure it is always present so users can see the effective packaging value.
+        if (pom.getPackaging() == null || "jar".equals(pom.getPackaging())) {
+            String packaging = pom.getPackaging() != null ? pom.getPackaging() : project.getPackaging();
+            String packagingTag = "  <packaging>" + packaging + "</packaging>";
+            if (!effectivePom.contains(packagingTag)) {
+                effectivePom = effectivePom.replace("</version>" + LS, "</version>" + LS + packagingTag + LS);
+            }
+        }
+
         writeComment(writer, "Effective POM for project '" + project.getId() + "'");
 
         writer.writeMarkup(effectivePom);