Skip Java 9-14 in reproducible test

src/it/projects/reproducible/invoker.properties

@@ -14,4 +14,12 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
+
+# javadoc has some annoying bugs that make the output unreproducible:
+# See: https://issues.apache.org/jira/browse/MJAVADOC-681
+# https://bugs.openjdk.org/browse/JDK-8268771
+# https://bugs.openjdk.org/browse/JDK-8237909
+
+# To create "reproducible" javadoc you need to use Java 8 or Java 15+
+invoker.java.version = 1.8, 15+
 invoker.goals = compile javadoc:jar

src/it/projects/reproducible/pom.xml

@@ -26,6 +26,8 @@
   <artifactId>bar</artifactId>
   <version>0.1.0-SNAPSHOT</version>
 
+  <inceptionYear>2010</inceptionYear>
+
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <maven.compiler.source>@maven.compiler.source@</maven.compiler.source>
@@ -39,9 +41,6 @@
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-javadoc-plugin</artifactId>
         <version>@project.version@</version>
-        <configuration>
-          <notimestamp>true</notimestamp>
-        </configuration>
       </plugin>
     </plugins>
   </build>

src/it/projects/reproducible/verify.groovy

@@ -29,7 +29,7 @@ assert apidocs.isDirectory()
 
 def options = new File( apidocs, 'options' )
 assert options.isFile()
-assert options.text.contains( "'Copyright © 2020. All rights reserved.'" )
+assert options.text.contains( "'Copyright © 2010–2020. All rights reserved.'" )
 
 def artifact = new File( target, 'bar-0.1.0-SNAPSHOT-javadoc.jar' )
 assert artifact.isFile()
@@ -39,7 +39,8 @@ apidocs.eachFileRecurse
 {
     if ( it.name.endsWith( '.html' ) )
     {
-        assert it.text =~ /<!-- Generated by javadoc (\(\d+\) )?-->/
+        def line = it.text.readLines().find { it.startsWith( "<!-- Generated by javadoc" ) }
+        assert line ==~ /<!-- Generated by javadoc (\(\d+\) )?-->/
     }
 }
 
@@ -53,13 +54,8 @@ long normalizeUTC( String timestamp )
 }
 
 JarFile jar = new JarFile( artifact )
+assert jar.stream().count() > 0
 
 // All entries should have the same timestamp
 FileTime expectedTimestamp = FileTime.fromMillis( normalizeUTC( "2020-02-29T23:59:58Z" ) )
-def testTimestamp =
-{
-    JarEntry entry -> assert expectedTimestamp.equals( entry.getLastModifiedTime() )
-}
-
-jar.stream().forEach( testTimestamp )
-jar.close()
+jar.stream().forEach { assert expectedTimestamp.equals( it.getLastModifiedTime() ) }

src/main/java/org/apache/maven/plugins/javadoc/AbstractJavadocMojo.java

@@ -1286,14 +1286,16 @@ public abstract class AbstractJavadocMojo
 
     /**
      * Suppresses the timestamp, which is hidden in an HTML comment in the generated HTML near the top of each page.
-     * <br/>
+     * <br><br>
+     * <strong>Note:</strong> If the project has the property <code>project.build.outputTimestamp</code>, the value
+     * will be overwritten to true. This way it is possible to generate reproducible javadoc jars.
+     * <br><br>
      * See
      * <a href="https://docs.oracle.com/javase/7/docs/technotes/tools/windows/javadoc.html#notimestamp">notimestamp</a>.
-     * <br/>
+     * <br>
      * Since
      * <a href="https://docs.oracle.com/javase/7/docs/technotes/guides/javadoc/whatsnew-1.5.0.html#commandlineoptions">
      * Java 5.0</a>.
-     * <br/>
      *
      * @since 2.1
      */
@@ -5654,7 +5656,7 @@ private void addStandardDocletOptions( File javadocOutputDirectory,
 
         addArgIf( arguments, nosince, "-nosince" );
 
-        if ( MavenArchiver.parseBuildOutputTimestamp( outputTimestamp ).isPresent() )
+        if ( !notimestamp && MavenArchiver.parseBuildOutputTimestamp( outputTimestamp ).isPresent() )
         {
             // Override the notimestamp option if a Reproducible Build is requested.
             notimestamp = true;