Add an integration test for a multi-release project defined with the new <source> element.

Author: desruisseaux

src/it/multirelease-on-classpath/invoker.properties

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+# 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 = clean compile
+invoker.buildResult = success

src/it/multirelease-on-classpath/pom.xml

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+<?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/4.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.1.0 http://maven.apache.org/xsd/maven-4.1.0.xsd">
+  <modelVersion>4.1.0</modelVersion>
+  <groupId>org.apache.maven.plugins</groupId>
+  <artifactId>multirelease-on-classpath</artifactId>
+  <version>1.0-SNAPSHOT</version>
+  <packaging>jar</packaging>
+  <name>Mulirelease in Maven 4</name>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>@project.version@</version>
+        <configuration>
+          <!-- TODO: remove source and target after we identified where Maven inherits those values. -->
+          <source />
+          <target />
+        </configuration>
+      </plugin>
+    </plugins>
+
+    <sources>
+      <source>
+        <directory>src/main/java</directory>
+        <targetVersion>15</targetVersion>
+      </source>
+      <source>
+        <directory>src/main/java_16</directory>
+        <targetVersion>16</targetVersion>
+      </source>
+      <source>
+        <directory>src/main/java_17</directory>
+        <targetVersion>17</targetVersion>
+      </source>
+    </sources>
+  </build>
+</project>

src/it/multirelease-on-classpath/src/main/java/foo/MainFile.java

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+/*
+ * 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 foo;
+
+/**
+ * Test {@code <Source>}.
+ * Another {@code <Source>}.
+ */
+public class MainFile {
+    public static void main(String[] args) {
+        System.out.println("MainFile");
+    }
+}

src/it/multirelease-on-classpath/src/main/java/foo/OtherFile.java

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+/*
+ * 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 foo;
+
+/**
+ * Test {@code <Source>}.
+ * Another {@code <Source>}.
+ */
+public class OtherFile {
+    public static void main(String[] args) {
+        System.out.println("OtherFile");
+    }
+}

src/it/multirelease-on-classpath/src/main/java_16/foo/OtherFile.java

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+/*
+ * 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 foo;
+
+/**
+ * Test {@code <Source>}.
+ * Another {@code <Source>}.
+ */
+public class OtherFile {
+    public static void main(String[] args) {
+        System.out.println("OtherFile on Java 16");
+        MainFile.main(args); // Verify that we have access to the base version.
+    }
+
+    static void requireJava16() {
+        System.out.println("Method available only on Java 16+");
+    }
+}

src/it/multirelease-on-classpath/src/main/java_17/foo/YetAnotherFile.java

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+/*
+ * 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 foo;
+
+/**
+ * Test {@code <Source>}.
+ * Another {@code <Source>}.
+ */
+class YetAnotherFile {
+    static void main(String[] args) {
+        System.out.println("YetAnotherFile on Java 17");
+        MainFile.main(args); // Verify that we have access to the base version.
+        OtherFile.requireJava16(); // Verify that we have access to the Java 16 version.
+    }
+}

src/it/multirelease-on-classpath/verify.groovy

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+/*
+ * 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.util.jar.JarFile
+
+def baseVersion = 59; // Java 15
+def nextVersion = 60; // Java 16
+def lastVersion = 61; // Java 17
+
+assert baseVersion == getMajor(new File( basedir, "target/classes/foo/MainFile.class"))
+assert baseVersion == getMajor(new File( basedir, "target/classes/foo/OtherFile.class"))
+assert nextVersion == getMajor(new File( basedir, "target/classes/META-INF/versions/16/foo/OtherFile.class"))
+assert lastVersion == getMajor(new File( basedir, "target/classes/META-INF/versions/17/foo/YetAnotherFile.class"))
+
+int getMajor(File file)
+{
+  assert file.exists()
+  def dis = new DataInputStream(new FileInputStream(file))
+  final String firstFourBytes = Integer.toHexString(dis.readUnsignedShort()) + Integer.toHexString(dis.readUnsignedShort())
+  if (!firstFourBytes.equalsIgnoreCase("cafebabe"))
+  {
+    throw new IllegalArgumentException(dataSourceName + " is not a Java .class file.")
+  }
+  final int minorVersion = dis.readUnsignedShort()
+  final int majorVersion = dis.readUnsignedShort()
+
+  dis.close()
+  return majorVersion
+}