[MJAVADOC-812] [REGRESSION] maven-javadoc-plugin 3.10.0 creates empty JARs

This closes #320

Author: michael-o

src/it/projects/MJAVADOC-812/invoker.properties

@@ -0,0 +1,19 @@
+# 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 = javadoc:jar
+

src/it/projects/MJAVADOC-812/pom.xml

@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+~   Licensed 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 xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>org.apache.maven.plugins.javadoc.it</groupId>
+    <artifactId>mjavadoc812</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <packaging>jar</packaging>
+
+    <url>https://issues.apache.org/jira/browse/MJAVADOC-812</url>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>@project.version@</version>
+            </plugin>
+        </plugins>
+    </build>
+</project>

src/it/projects/MJAVADOC-812/verify.groovy

@@ -0,0 +1,22 @@
+/*
+ * 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 javadocJar = new File( basedir, 'target/mjavadoc812-1.0-SNAPSHOT-javadoc.jar')
+
+assert !javadocJar.exists()

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

@@ -171,24 +171,28 @@ protected void doExecute() throws MojoExecutionException {
             failOnError("RuntimeException: Error while generating Javadoc", e);
         }
 
-        try {
-            File outputFile = generateArchive(
-                    new File(getPluginReportOutputDirectory()), finalName + "-" + getClassifier() + ".jar");
-
-            if (!attach) {
-                getLog().info("NOT adding javadoc to attached artifacts list.");
-            } else {
-                // TODO: these introduced dependencies on the project are going to become problematic - can we
-                // export it
-                //  through metadata instead?
-                projectHelper.attachArtifact(project, "javadoc", getClassifier(), outputFile);
+        File javadocOutputDirectory = new File(getPluginReportOutputDirectory());
+        if (javadocOutputDirectory.exists()) {
+            try {
+                File outputFile = generateArchive(javadocOutputDirectory, finalName + "-" + getClassifier() + ".jar");
+
+                if (!attach) {
+                    getLog().info("NOT adding javadoc to attached artifacts list.");
+                } else {
+                    // TODO: these introduced dependencies on the project are going to become problematic - can we
+                    // export it
+                    //  through metadata instead?
+                    projectHelper.attachArtifact(project, "javadoc", getClassifier(), outputFile);
+                }
+            } catch (ArchiverException e) {
+                failOnError("ArchiverException: Error while creating archive", e);
+            } catch (IOException e) {
+                failOnError("IOException: Error while creating archive", e);
+            } catch (RuntimeException e) {
+                failOnError("RuntimeException: Error while creating archive", e);
             }
-        } catch (ArchiverException e) {
-            failOnError("ArchiverException: Error while creating archive", e);
-        } catch (IOException e) {
-            failOnError("IOException: Error while creating archive", e);
-        } catch (RuntimeException e) {
-            failOnError("RuntimeException: Error while creating archive", e);
+        } else {
+            getLog().info("No Javadoc in project. Archive not created.");
         }
     }