[MCOMPILER-525] Incorrect detection of dependency change (#172)

Signed-off-by: Jorge Solórzano <jorsol@gmail.com>
Co-authored-by: Guillaume Nodet <gnodet@gmail.com>

src/it/MCOMPILER-525/invoker.properties

@@ -0,0 +1,21 @@
+# 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.
+
+# NOTE: The first time, we run up to "integration-test" phase which includes the AntRun execution which saves the
+# timestamp of the first JAR for comparison with the timestamp of the JAR from the final "package" invocation.
+# Note:
+invoker.goals = clean integration-test package -Dmaven.compiler.showCompilationChanges=true

src/it/MCOMPILER-525/pom.xml

@@ -0,0 +1,64 @@
+<?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/maven-v4_0_0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>org.apache.maven.plugins</groupId>
+  <artifactId>MCOMPILER-525-no-recreation</artifactId>
+  <name>MCOMPILER-525-no-recreation</name>
+  <packaging>jar</packaging>
+  <version>1.0-SNAPSHOT</version>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>@project.version@</version>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-jar-plugin</artifactId>
+        <version>3.3.0</version>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-antrun-plugin</artifactId>
+        <version>3.1.0</version>
+        <executions>
+          <execution>
+            <id>touch</id>
+            <phase>integration-test</phase>
+            <goals>
+              <goal>run</goal>
+            </goals>
+            <configuration>
+              <target>
+                <!-- Save the JAR and especially its timestamp for evaluation by the post-build hook script -->
+                <copy file="target/MCOMPILER-525-no-recreation-1.0-SNAPSHOT.jar"
+                      tofile="target/reference.jar"
+                      preservelastmodified="true" overwrite="true"/>
+              </target>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>

src/it/MCOMPILER-525/src/main/java/myproject/HelloWorld.java

@@ -0,0 +1,34 @@
+/*
+ * 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.
+ */
+package myproject;
+
+/**
+ * The classic Hello World App.
+ */
+public class HelloWorld {
+
+    /**
+     * Main method.
+     *
+     * @param args Not used
+     */
+    public static void main(String[] args) {
+        System.out.println("Hi!");
+    }
+}

src/it/MCOMPILER-525/verify.groovy

@@ -0,0 +1,44 @@
+
+/*
+ * 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 java.nio.file.*;
+import java.time.*;
+import java.time.temporal.*
+import java.util.*;
+
+File target = new File( basedir, "target" );
+assert target.isDirectory()
+
+File jarFile = new File( target, "MCOMPILER-525-no-recreation-1.0-SNAPSHOT.jar" );
+assert jarFile.isFile()
+
+File refFile = new File( target, "reference.jar" );
+assert refFile.isFile()
+
+Instant referenceTimestamp = Files.getLastModifiedTime( refFile.toPath() )
+    .toInstant().truncatedTo( ChronoUnit.MILLIS );
+System.out.println( "Reference timestamp: " + referenceTimestamp );
+
+Instant actualTimestamp = Files.getLastModifiedTime( jarFile.toPath() )
+    .toInstant().truncatedTo( ChronoUnit.MILLIS );
+System.out.println( "Actual timestamp   : " + actualTimestamp );
+
+assert referenceTimestamp.equals(actualTimestamp),
+    "Timestamps don't match, JAR was recreated although contents has not changed"

src/main/java/org/apache/maven/plugin/compiler/AbstractCompilerMojo.java

@@ -1538,7 +1538,7 @@ protected boolean isDependencyChanged() {
         for (String pathElement : pathElements) {
             File artifactPath = new File(pathElement);
             if (artifactPath.isDirectory() || artifactPath.isFile()) {
-                if (hasNewFile(artifactPath, buildStartTime)) {
+                if (!artifactPath.equals(getOutputDirectory()) && hasNewFile(artifactPath, buildStartTime)) {
                     if (showCompilationChanges) {
                         getLog().info("New dependency detected: " + artifactPath.getAbsolutePath());
                     } else {