[Fixes #807] The NonNull annotation can now be used documentary style on params of abstract methods. The warning has been eliminated.

doc/changelog.markdown

@@ -3,6 +3,7 @@ Lombok Changelog
 
 ### v1.16.7 "Edgy Guinea Pig"
 * BUGFIX: `@Value` and `@FieldDefaults` no longer make uninitialized static fields final. [Issue #928](https://github.com/rzwitserloot/lombok/issues/928).
+* ENHANCEMENT: Putting `@NonNull` on a parameter of an abstract method no longer generates a warning, to allow you to use this annotation to document intended behaviour [Issue #807](https://github.com/rzwitserloot/lombok/issues/807).
 
 ### v1.16.6 (August 18th, 2015)
 * FEATURE: `@Helper` can be placed on method-local inner classes to make all methods in the class accessible to the rest of the method. [Full documentation](https://projectlombok.org/features/experimental/Helper.html).

src/core/lombok/eclipse/handlers/HandleNonNull.java

@@ -91,7 +91,7 @@ public class HandleNonNull extends EclipseAnnotationHandler<NonNull> {
 		if (isGenerated(declaration)) return;
 		
 		if (declaration.isAbstract()) {
-			annotationNode.addWarning("@NonNull is meaningless on a parameter of an abstract method.");
+			// This used to be a warning, but as @NonNull also has a documentary purpose, better to not warn about this. Since 1.16.7
 			return;
 		}
 		

src/core/lombok/javac/handlers/HandleNonNull.java

@@ -85,7 +85,7 @@ public class HandleNonNull extends JavacAnnotationHandler<NonNull> {
 		}
 		
 		if (declaration.body == null) {
-			annotationNode.addWarning("@NonNull is meaningless on a parameter of an abstract method.");
+			// This used to be a warning, but as @NonNull also has a documentary purpose, better to not warn about this. Since 1.16.7
 			return;
 		}
 		

test/transform/resource/after-delombok/NonNullOnParameterOfDefaultMethod.java

@@ -0,0 +1,9 @@
+interface NonNullOnParameterOfDefaultMethod {
+	void test(@lombok.NonNull String arg);
+	default void test2(@lombok.NonNull String arg) {
+		if (arg == null) {
+			throw new java.lang.NullPointerException("arg");
+		}
+		System.out.println(arg);
+	}
+}

test/transform/resource/after-ecj/NonNullOnParameterOfDefaultMethod.java

@@ -0,0 +1,10 @@
+interface NonNullOnParameterOfDefaultMethod {
+  void test(@lombok.NonNull String arg);
+  default void test2(@lombok.NonNull String arg) {
+    if ((arg == null))
+        {
+          throw new java.lang.NullPointerException("arg");
+        }
+    System.out.println(arg);
+  }
+}

test/transform/resource/before/NonNullOnParameterOfDefaultMethod.java

@@ -0,0 +1,6 @@
+interface NonNullOnParameterOfDefaultMethod {
+	void test(@lombok.NonNull String arg);
+	default void test2(@lombok.NonNull String arg) {
+		System.out.println(arg);
+	}
+}

test/transform/resource/messages-delombok/NonNullOnParameterAbstract.java.messages

@@ -1 +0,0 @@
-6 @NonNull is meaningless on a parameter of an abstract method.

test/transform/resource/messages-ecj/NonNullOnParameterAbstract.java.messages

@@ -1 +0,0 @@
-6 @NonNull is meaningless on a parameter of an abstract method.

test/transform/resource/messages-idempotent/NonNullOnParameterAbstract.java.messages

@@ -1 +0,0 @@
-9 @NonNull is meaningless on a parameter of an abstract method.

website/features/NonNull.html

@@ -15,7 +15,7 @@
 		<div class="overview">
 			<h3>Overview</h3>
 			<p>
-			<em>NEW in Lombok 0.11.10: </em>You can use <code>@NonNull</code> on the parameter of a method or constructor to have lombok generate a null-check statement for you.
+			<em>NEW in Lombok 0.11.10: </em>You can use <code>@NonNull</code> on the parameter of a method or constructor to have lombok generate a null-check statement for you.<br />
 			</p><p>
 				Lombok has always treated any annotation named <code>@NonNull</code> on a field as a signal to generate a null-check if lombok generates an entire method or constructor for you, via
 				for example <a href="Data.html"><code>@Data</code></a>. Now, however, using lombok's own <code>@lombok.NonNull</code> on a parameter results in the insertion of just the null-check
@@ -60,6 +60,9 @@
 				this feature only triggers on lombok's own <code>@NonNull</code> annotation from the <code>lombok</code> package.
 				</p><p>
 				A <code>@NonNull</code> on a primitive parameter results in a warning. No null-check will be generated.
+				</p><p>
+				A <code>@NonNull</code> on a parameter of an abstract method used to generate a warning; starting with version 1.16.8, this is no longer the case, to acknowledge the notion that <code>@NonNull</code> also has a
+				documentary role. For the same reason, you can annotate a method as <code>@NonNull</code>; this is allowed, generates no warning, and does not generate any code.
 				</p>
 			</div>
 		</div>