[MCOMPILER-391] Use dep mgmt when resolving annotation processors and…

… their deps

 * dependency managemet can be used for two slighty difference use
   cases (when it comes to annotation processor dependencies):
     -- getting the version of the top-level processor path elements
     -- passing the list of managed dependencies to maven-resolver
        when resolving the whole processorpath
   These two can be combined, so there is total of 4 combinations (some of
   the them make more sense than the others, but generally there is
   no reason to not support all of them)

 * using dependency management when resolving transitive dependencies of
   annotation processors is something that may or may not be desired.
   For that reason, there is a new flag that explicitly enables this
   behavior, while default is to _not_ use dependency management
   (the current behavior)

src/it/MCOMPILER-391-processorpath-dep-mgmt/annotation-api/pom.xml

@@ -0,0 +1,34 @@
+<?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>
+
+  <parent>
+    <groupId>org.apache.maven.plugins.compiler.it</groupId>
+    <artifactId>mcompiler391-test</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>mcompiler391-annotation-api</artifactId>
+
+</project>

src/it/MCOMPILER-391-processorpath-dep-mgmt/annotation-api/src/main/java/mcompiler391/SimpleAnnotation.java

@@ -0,0 +1,35 @@
+/*
+ * 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 mcompiler391;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.SOURCE)
+public @interface SimpleAnnotation {
+    /**
+     * Specifies which classes (FQCNs) are supposed to be on classpath during annotation processing.
+     * Used to check if the dependency resolution mechanism of maven-compiler-plugin is constructing
+     * the classpath (processorpath) correctly, based on the plugin configuration and dependency management.
+     */
+    String[] onClasspath() default "";
+}

src/it/MCOMPILER-391-processorpath-dep-mgmt/annotation-processor-dep-v1/pom.xml

@@ -0,0 +1,34 @@
+<?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>
+
+  <parent>
+    <groupId>org.apache.maven.plugins.compiler.it</groupId>
+    <artifactId>mcompiler391-test</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>mcompiler391-annotation-processor-dep</artifactId>
+
+</project>

src/it/MCOMPILER-391-processorpath-dep-mgmt/annotation-processor-dep-v1/src/main/java/mcompiler391/AnnotationProcessorDependencyV1.java

@@ -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.
+ */
+package mcompiler391;
+
+public class AnnotationProcessorDependencyV1 {}

src/it/MCOMPILER-391-processorpath-dep-mgmt/annotation-processor-dep-v2/pom.xml

@@ -0,0 +1,37 @@
+<?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>
+
+  <parent>
+    <groupId>org.apache.maven.plugins.compiler.it</groupId>
+    <artifactId>mcompiler391-test</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+  </parent>
+
+  <!-- Same groupId + artifactId as for v1 (1.0.0-SNAPSHOT), but different version to test version overrides
+       via dependency management -->
+  <artifactId>mcompiler391-annotation-processor-dep</artifactId>
+  <version>2.0.0-SNAPSHOT</version>
+
+</project>

src/it/MCOMPILER-391-processorpath-dep-mgmt/annotation-processor-dep-v2/src/main/java/mcompiler391/AnnotationProcessorDependencyV2.java

@@ -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.
+ */
+package mcompiler391;
+
+public class AnnotationProcessorDependencyV2 {}

src/it/MCOMPILER-391-processorpath-dep-mgmt/annotation-processor/pom.xml

@@ -0,0 +1,47 @@
+<?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>
+
+  <parent>
+    <groupId>org.apache.maven.plugins.compiler.it</groupId>
+    <artifactId>mcompiler391-test</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>mcompiler391-annotation-processor</artifactId>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.apache.maven.plugins.compiler.it</groupId>
+      <artifactId>mcompiler391-annotation-api</artifactId>
+      <version>1.0.0-SNAPSHOT</version>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.maven.plugins.compiler.it</groupId>
+      <artifactId>mcompiler391-annotation-processor-dep</artifactId>
+      <version>1.0.0-SNAPSHOT</version>
+    </dependency>
+  </dependencies>
+
+</project>

src/it/MCOMPILER-391-processorpath-dep-mgmt/annotation-processor/src/main/java/mcompiler391/SimpleAnnotationProcessor.java

@@ -0,0 +1,89 @@
+/*
+ * 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 mcompiler391;
+
+import javax.annotation.processing.AbstractProcessor;
+import javax.annotation.processing.Filer;
+import javax.annotation.processing.RoundEnvironment;
+import javax.annotation.processing.SupportedAnnotationTypes;
+import javax.annotation.processing.SupportedSourceVersion;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.Name;
+import javax.lang.model.element.PackageElement;
+import javax.lang.model.element.TypeElement;
+import javax.lang.model.util.Elements;
+import javax.tools.FileObject;
+import javax.tools.StandardLocation;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.util.Set;
+
+@SupportedSourceVersion(SourceVersion.RELEASE_6)
+@SupportedAnnotationTypes("mcompiler391.SimpleAnnotation")
+public class SimpleAnnotationProcessor extends AbstractProcessor {
+
+    @Override
+    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
+        if (annotations.isEmpty()) {
+            return true;
+        }
+
+        Filer filer = processingEnv.getFiler();
+
+        Elements elementUtils = processingEnv.getElementUtils();
+
+        Set<? extends Element> elements =
+                roundEnv.getElementsAnnotatedWith(annotations.iterator().next());
+
+        for (Element element : elements) {
+            Name name = element.getSimpleName();
+            PackageElement packageElement = elementUtils.getPackageOf(element);
+
+            SimpleAnnotation annotation = element.getAnnotation(SimpleAnnotation.class);
+            assertClassesAreOnClasspath(annotation.onClasspath());
+
+            try {
+                Name packageName = packageElement.getQualifiedName();
+                FileObject resource =
+                        filer.createResource(StandardLocation.SOURCE_OUTPUT, packageName, name + ".txt", element);
+
+                Writer writer = resource.openWriter();
+                writer.write(name.toString());
+                writer.close();
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return !elements.isEmpty();
+    }
+
+    private void assertClassesAreOnClasspath(String[] fqcns) {
+        for (String fqcn : fqcns) {
+            try {
+                getClass().getClassLoader().loadClass(fqcn);
+            } catch (ClassNotFoundException cnfe) {
+                String msg = String.format(
+                        "Expected class '%s' to be on the classpath (processorpath), " + "but it wasn't.", fqcn);
+                throw new RuntimeException(msg, cnfe);
+            }
+        }
+    }
+}