[MPLUGIN-390] Do not overwrite generate files with no content change

maven-plugin-plugin/src/it/mplugin-390/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.1 = process-classes
+invoker.goals.2 = process-classes

maven-plugin-plugin/src/it/mplugin-390/pom.xml

@@ -0,0 +1,114 @@
+<?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 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>org.apache.maven.its.mplugin-390</groupId>
+  <artifactId>mplugin-390</artifactId>
+  <version>1.0-SNAPSHOT</version>
+  <packaging>maven-plugin</packaging>
+
+  <name>Maven Integration Test :: mplugin-390</name>
+  <description>
+    Test plugin-plugin, plugin.xml descriptor - shouldn't contain dependencies in provided scope
+  </description>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.apache.maven</groupId>
+      <artifactId>maven-plugin-api</artifactId>
+      <version>@mavenVersion@</version>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.maven.plugin-tools</groupId>
+      <artifactId>maven-plugin-annotations</artifactId>
+      <version>@project.version@</version>
+      <scope>provided</scope>
+    </dependency>
+
+    <!-- dependency in compile scope -->
+    <dependency>
+      <groupId>org.apache.commons</groupId>
+      <artifactId>commons-math3</artifactId>
+      <version>3.6.1</version>
+    </dependency>
+
+    <!-- dependency in runtime scope -->
+    <dependency>
+      <groupId>org.apache.commons</groupId>
+      <artifactId>commons-rng-client-api</artifactId>
+      <version>1.4</version>
+      <scope>runtime</scope>
+    </dependency>
+
+  </dependencies>
+
+  <build>
+    <pluginManagement>
+      <plugins>
+        <plugin>
+          <groupId>org.apache.maven.plugins</groupId>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.1</version>
+          <configuration>
+            <source>1.8</source>
+            <target>1.8</target>
+          </configuration>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-antrun-plugin</artifactId>
+        <version>3.0.0</version>
+        <executions>
+          <execution>
+            <id>touch</id>
+            <phase>generate-resources</phase>
+            <goals>
+              <goal>run</goal>
+            </goals>
+            <configuration>
+              <target>
+                <touch file="${project.build.directory}/touch.txt"/>
+                <sleep milliseconds="100"/>
+              </target>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-plugin-plugin</artifactId>
+        <version>@project.version@</version>
+      </plugin>
+    </plugins>
+
+  </build>
+</project>

maven-plugin-plugin/src/it/mplugin-390/src/main/java/org/apache/maven/plugin/coreit/FirstMojo.java

@@ -0,0 +1,53 @@
+package org.apache.maven.plugin.coreit;
+
+/*
+ * 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.apache.maven.plugin.AbstractMojo;
+import org.apache.maven.plugin.MojoExecutionException;
+import org.apache.maven.plugins.annotations.Component;
+import org.apache.maven.plugins.annotations.ResolutionScope;
+import org.apache.maven.plugins.annotations.Execute;
+import org.apache.maven.plugins.annotations.LifecyclePhase;
+import org.apache.maven.plugins.annotations.Mojo;
+import org.apache.maven.plugins.annotations.Parameter;
+
+/**
+ * Touches a test file.
+ *
+ * @since 1.2
+ */
+@Mojo( name = "first", requiresDependencyResolution = ResolutionScope.TEST, defaultPhase = LifecyclePhase.INTEGRATION_TEST )
+public class FirstMojo
+    extends AbstractMojo
+{
+
+    /**
+     * @since 0.1
+     * @deprecated As of 0.2
+     */
+    @Parameter( alias = "alias" )
+    private String aliasedParam;
+
+    public void execute()
+        throws MojoExecutionException
+    {
+        // nothing
+    }
+}

maven-plugin-plugin/src/it/mplugin-390/verify.groovy

@@ -0,0 +1,29 @@
+/*
+ * 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.
+ */
+
+File descriptorFile = new File( basedir, "target/classes/META-INF/maven/plugin.xml" );
+assert descriptorFile.isFile()
+
+File touchFile = new File( basedir, "target/touch.txt" );
+assert touchFile.isFile()
+
+// the touch file should be newer than the descriptor
+assert touchFile.lastModified() > descriptorFile.lastModified()
+
+return true;

maven-plugin-tools-generators/src/main/java/org/apache/maven/tools/plugin/generator/PluginDescriptorGenerator.java

@@ -20,7 +20,6 @@
  */
 
 import java.io.File;
-import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStreamWriter;
 import java.io.Writer;
@@ -39,6 +38,7 @@
 import org.apache.maven.tools.plugin.PluginToolsRequest;
 import org.apache.maven.tools.plugin.util.PluginUtils;
 import org.codehaus.plexus.util.StringUtils;
+import org.codehaus.plexus.util.io.CachingOutputStream;
 import org.codehaus.plexus.util.xml.PrettyPrintXMLWriter;
 import org.codehaus.plexus.util.xml.XMLWriter;
 
@@ -89,16 +89,12 @@ public void writeDescriptor( File destinationFile, PluginToolsRequest request, b
     {
         PluginDescriptor pluginDescriptor = request.getPluginDescriptor();
 
-        if ( destinationFile.exists() )
-        {
-            destinationFile.delete();
-        }
-        else if ( !destinationFile.getParentFile().exists() )
+        if ( !destinationFile.getParentFile().exists() )
         {
             destinationFile.getParentFile().mkdirs();
         }
 
-        try ( Writer writer = new OutputStreamWriter( new FileOutputStream( destinationFile ), UTF_8 ) )
+        try ( Writer writer = new OutputStreamWriter( new CachingOutputStream( destinationFile ), UTF_8 ) )
         {
             XMLWriter w = new PrettyPrintXMLWriter( writer, UTF_8.name(), null );
 

maven-plugin-tools-generators/src/main/java/org/apache/maven/tools/plugin/generator/PluginHelpGenerator.java

@@ -23,15 +23,17 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
 import java.io.StringWriter;
+import java.io.Writer;
 
 import org.apache.maven.project.MavenProject;
 import org.apache.velocity.VelocityContext;
 import org.codehaus.plexus.logging.AbstractLogEnabled;
 import org.codehaus.plexus.logging.Logger;
 import org.codehaus.plexus.logging.console.ConsoleLogger;
-import org.codehaus.plexus.util.FileUtils;
 import org.codehaus.plexus.util.StringUtils;
+import org.codehaus.plexus.util.io.CachingOutputStream;
 import org.codehaus.plexus.velocity.VelocityComponent;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
@@ -84,7 +86,10 @@ public void execute( File destinationDirectory )
             String helpClassSources =
                 getHelpClassSources( getPluginHelpPath( mavenProject ) );
 
-            FileUtils.fileWrite( helpClass, UTF_8.name(), helpClassSources );
+            try ( Writer w = new OutputStreamWriter( new CachingOutputStream( helpClass ), UTF_8 ) )
+            {
+                w.write( helpClassSources );
+            }
         }
         catch ( IOException e )
         {

maven-plugin-tools-generators/src/main/java/org/apache/maven/tools/plugin/generator/PluginXdocGenerator.java

@@ -27,11 +27,11 @@
 import org.apache.maven.tools.plugin.ExtendedMojoDescriptor;
 import org.apache.maven.tools.plugin.PluginToolsRequest;
 import org.codehaus.plexus.util.StringUtils;
+import org.codehaus.plexus.util.io.CachingOutputStream;
 import org.codehaus.plexus.util.xml.PrettyPrintXMLWriter;
 import org.codehaus.plexus.util.xml.XMLWriter;
 
 import java.io.File;
-import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStreamWriter;
 import java.io.PrintWriter;
@@ -133,7 +133,7 @@ protected void processMojoDescriptor( MojoDescriptor mojoDescriptor, File destin
         throws IOException
     {
         File outputFile = new File( destinationDirectory, getMojoFilename( mojoDescriptor, "xml" ) );
-        try ( Writer writer = new OutputStreamWriter( new FileOutputStream( outputFile ), UTF_8 ) )
+        try ( Writer writer = new OutputStreamWriter( new CachingOutputStream( outputFile ), UTF_8 ) )
         {
             XMLWriter w = new PrettyPrintXMLWriter( new PrintWriter( writer ), UTF_8.name(), null );
             writeBody( mojoDescriptor, w );