feat: Add modernizer plugin

Author: jeffjensen

src/main/resources/META-INF/archetype-post-generate.groovy

@@ -215,6 +215,7 @@ ${modulesXml}
     <maven-failsafe-plugin.version>3.5.5</maven-failsafe-plugin.version>
     <maven-jar-plugin.version>3.4.2</maven-jar-plugin.version>
     <maven-surefire-plugin.version>3.5.5</maven-surefire-plugin.version>
+    <modernizer-maven-plugin.version>3.4.0</modernizer-maven-plugin.version>
   </properties>
 
   <dependencyManagement>
@@ -271,8 +272,31 @@ ${dmXml}
             <argLine>-XX:MaxRAMPercentage=5.0</argLine>
           </configuration>
         </plugin>
+        <plugin>
+          <groupId>org.gaul</groupId>
+          <artifactId>modernizer-maven-plugin</artifactId>
+          <version>\${modernizer-maven-plugin.version}</version>
+          <configuration>
+            <javaVersion>\${java.version}</javaVersion>
+          </configuration>
+          <executions>
+            <execution>
+              <id>modernizer</id>
+              <phase>verify</phase>
+              <goals>
+                <goal>modernizer</goal>
+              </goals>
+            </execution>
+          </executions>
+        </plugin>
       </plugins>
     </pluginManagement>
+    <plugins>
+      <plugin>
+        <groupId>org.gaul</groupId>
+        <artifactId>modernizer-maven-plugin</artifactId>
+      </plugin>
+    </plugins>
   </build>
 </project>
 """

src/site/asciidoc/modules.adoc

@@ -92,7 +92,9 @@ It contains:
 * `<dependencyManagement>` — all modules pinned to `${project.version}`, sorted alphabetically by `artifactId`
 * Common properties: Java 21 via `maven.compiler.release`; UTF-8 source encoding
 * `<pluginManagement>` — pinned versions for `maven-compiler-plugin`, `maven-failsafe-plugin`,
-  `maven-jar-plugin` (with `skipIfEmpty=true`), and `maven-surefire-plugin`
+  `maven-jar-plugin` (with `skipIfEmpty=true`), `maven-surefire-plugin`, and
+  `modernizer-maven-plugin` (bound to `verify`, `javaVersion` = `${java.version}`)
+* `<plugins>` — activates `modernizer-maven-plugin` so every module is checked for outdated API usage during `verify`
 
 To build a generated project:
 

src/site/asciidoc/requirements.adoc

@@ -59,7 +59,10 @@ Do not create a `pom.xml` at the project root.
   `project.build.sourceEncoding`.
 * `<pluginManagement>` — declare pinned versions for `maven-compiler-plugin`,
   `maven-failsafe-plugin`, `maven-jar-plugin` (configured with `skipIfEmpty=true`),
-  and `maven-surefire-plugin`.
+  `maven-surefire-plugin`, and `modernizer-maven-plugin` (bound to the `verify`
+  phase with `javaVersion` set to `${java.version}`).
+* `<plugins>` — activate `modernizer-maven-plugin` so every module is checked for
+  outdated API usage during `verify`.
 
 === Child module POMs
 

src/test/resources/projects/basic/verify.groovy

@@ -63,6 +63,25 @@ assert parentPom.contains('<artifactId>maven-jar-plugin</artifactId>')      : 'p
 assert parentPom.contains('<artifactId>maven-surefire-plugin</artifactId>') : 'parent must declare maven-surefire-plugin in pluginManagement'
 assert parentPom.contains('<skipIfEmpty>true</skipIfEmpty>')                 : 'maven-jar-plugin must configure skipIfEmpty=true'
 
+// modernizer-maven-plugin: pinned, managed in pluginManagement, activated in build/plugins
+assert parentPom.contains('<modernizer-maven-plugin.version>3.4.0</modernizer-maven-plugin.version>') \
+    : 'parent must pin modernizer-maven-plugin version'
+assert parentPom.count('<artifactId>modernizer-maven-plugin</artifactId>') == 2 \
+    : 'modernizer-maven-plugin must appear twice: once in pluginManagement, once in active plugins'
+
+def pmBlock = (parentPom =~ /(?s)<pluginManagement>.*<\/pluginManagement>/)[0]
+assert pmBlock.contains('<groupId>org.gaul</groupId>')                       : 'modernizer must use groupId org.gaul'
+assert pmBlock.contains('<artifactId>modernizer-maven-plugin</artifactId>') : 'modernizer must be declared in pluginManagement'
+assert pmBlock.contains('<version>${modernizer-maven-plugin.version}</version>') : 'modernizer pluginManagement must reference the version property'
+assert pmBlock.contains('<javaVersion>${java.version}</javaVersion>')        : 'modernizer must configure javaVersion'
+assert pmBlock.contains('<goal>modernizer</goal>')                          : 'modernizer pluginManagement must bind the modernizer goal'
+
+// the active <plugins> section is what remains of <build> after removing <pluginManagement>
+def buildBlock    = (parentPom =~ /(?s)<build>.*<\/build>/)[0]
+def activePlugins = buildBlock.replaceAll(/(?s)<pluginManagement>.*<\/pluginManagement>/, '')
+assert activePlugins.contains('<artifactId>modernizer-maven-plugin</artifactId>') \
+    : 'modernizer-maven-plugin must be activated in the parent <build><plugins> section'
+
 // ── 5. Modules are sorted alphabetically in <modules> ────────────────────────
 
 def moduleOrder = modules.sort().collect { "<module>../${it}</module>" }