added annotation to find exact package for moxy reflector deleaget

moxy-compiler/src/main/java/com/arellomobile/mvp/compiler/MvpCompiler.java

@@ -1,6 +1,7 @@
 package com.arellomobile.mvp.compiler;
 
 import com.arellomobile.mvp.InjectViewState;
+import com.arellomobile.mvp.RegisterMoxyReflectorDelegate;
 import com.arellomobile.mvp.compiler.presenterbinder.InjectPresenterProcessor;
 import com.arellomobile.mvp.compiler.presenterbinder.PresenterBinderClassGenerator;
 import com.arellomobile.mvp.compiler.reflector.MoxyReflectorGenerator;
@@ -76,10 +77,12 @@ public synchronized void init(ProcessingEnvironment processingEnv) {
 	@Override
 	public Set<String> getSupportedAnnotationTypes() {
 		Set<String> supportedAnnotationTypes = new HashSet<>();
-		Collections.addAll(supportedAnnotationTypes,
+		Collections.addAll(
+		        supportedAnnotationTypes,
 				InjectPresenter.class.getCanonicalName(),
-				InjectViewState.class.getCanonicalName()
-		);
+				InjectViewState.class.getCanonicalName(),
+				RegisterMoxyReflectorDelegate.class.getCanonicalName()
+        );
 		return supportedAnnotationTypes;
 	}
 
@@ -141,16 +144,21 @@ private boolean throwableProcess(RoundEnvironment roundEnv) {
 		return true;
 	}
 
-	/**
-	 * @return first package associated with this module.
-	 * Probably should return module's top-level package
-	 */
 	private String getMoxyReflectorDelegatePackage(
 	        final RoundEnvironment roundEnv
     ) {
+        final Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(RegisterMoxyReflectorDelegate.class);
+
+        if (elements.isEmpty()) {
+            getMessager().printMessage(
+                    Diagnostic.Kind.ERROR,
+                    "Cannot find any class annotated with " + RegisterMoxyReflectorDelegate.class.getSimpleName() + " in this module"
+            );
+        }
+
 		return processingEnv
 				.getElementUtils()
-				.getPackageOf(roundEnv.getElementsAnnotatedWith(InjectPresenter.class).iterator().next())
+				.getPackageOf(elements.iterator().next())
 				.getQualifiedName()
 				.toString();
     }

moxy/src/main/java/com/arellomobile/mvp/RegisterMoxyReflectorDelegate.java

@@ -0,0 +1,11 @@
+package com.arellomobile.mvp;
+
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.TYPE;
+
+/**
+ * Register MoxyReflector package
+ */
+@Target(TYPE)
+public @interface RegisterMoxyReflectorDelegate {}