Added utility for debugging annotation processors.

src/main/groovy/com/xinra/nucleus/apt/NucleusProcessor.java

@@ -10,7 +10,7 @@
 import javax.tools.Diagnostic;
 
 /**
- * Base class for annotation Processors
+ * Base class for annotation Processors.
  * 
  * @author Erik Hofer
  */

src/main/groovy/com/xinra/nucleus/apt/testing/ProcessorTesting.java

@@ -0,0 +1,64 @@
+package com.xinra.nucleus.apt.testing;
+
+import java.io.File;
+import java.io.PrintWriter;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Set;
+import javax.annotation.processing.Processor;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaCompiler.CompilationTask;
+import javax.tools.JavaFileObject;
+import javax.tools.JavaFileObject.Kind;
+import javax.tools.StandardJavaFileManager;
+import javax.tools.StandardLocation;
+import javax.tools.ToolProvider;
+
+/**
+ * Used for debugging annotation processors.
+ */
+//based on http://stackoverflow.com/a/27560295/5519485
+public class ProcessorTesting {
+
+  private ProcessorTesting() {}
+
+  /**
+   * Compiles sources in the given directory and applies annotation processors.
+   * Include in a unit test:
+   * <pre>
+   * {@literal @Test}
+   * public void runAnnoationProcessor() throws Exception {
+   *   ProcessorTesting.compile("src/main/java", MyProcessor.class);
+   * }
+   * </pre>
+   * This way the annotation processor(s) can be debugged when running the
+   * test in debug mode.
+   * 
+   * @param sourcePath path of the source files to be compiled
+   * @param processors annotation processors that should be run on the code
+   */
+  public static void compile(String sourcePath, Processor... processors)
+      throws Exception {
+
+    Iterable<JavaFileObject> files = getSourceFiles(sourcePath);
+
+    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
+
+    CompilationTask task = 
+        compiler.getTask(new PrintWriter(System.out), null, null, null, null, files);
+    task.setProcessors(Arrays.asList(processors));
+
+    task.call();
+  }
+
+  private static Iterable<JavaFileObject> getSourceFiles(String path) throws Exception {
+    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
+    StandardJavaFileManager files = compiler.getStandardFileManager(null, null, null);
+
+    files.setLocation(StandardLocation.SOURCE_PATH, Arrays.asList(new File(path)));
+
+    Set<Kind> fileKinds = Collections.singleton(Kind.SOURCE);
+    return files.list(StandardLocation.SOURCE_PATH, "", fileKinds, true);
+  }
+
+}