Avoid generate @DeleGate method body NPE when deletegate target is nu…

…ll on javac's HandleDelegate

src/core/lombok/experimental/Delegate.java

@@ -1,16 +1,16 @@
 /*
  * Copyright (C) 2010-2017 The Project Lombok Authors.
- * 
+ *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
- * 
+ *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
- * 
+ *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
@@ -28,14 +28,14 @@
 
 /**
  * Put on any field to make lombok generate delegate methods that forward the call to this field.
- * 
+ * <p>
  * Example:
  * <pre>
  *     private &#64;Delegate List&lt;String&gt; foo;
  * </pre>
- * 
+ * <p>
  * will generate for example an {@code boolean add(String)} method, which contains: {@code return foo.add(arg);}, as well as all other methods in {@code List}.
- * 
+ * <p>
  * All public instance methods of the field's type, as well as all public instance methods of all the field's type's superfields are delegated, except for all methods
  * that exist in {@link Object}, the {@code canEqual(Object)} method, and any methods that appear in types
  * that are listed in the {@code excludes} property.
@@ -65,4 +65,11 @@
 	 * @return For each method (not already in {@code java.lang.Object}) in these types, skip generating a delegate method (overrides {@code types()}).
 	 */
 	Class<?>[] excludes() default {};
+
+	/**
+	 * If configuration turn to true. When field is null and target type delegate method return as a references type, just return a null instead of throw a NPE
+	 *
+	 * @return Is it needed to avoid NPE make the utmost effort.
+	 */
+	boolean skipAndReturnNullOnNullRef() default false;
 }

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

@@ -23,6 +23,8 @@
 
 import static com.sun.tools.javac.code.Flags.*;
 import static lombok.core.handlers.HandlerUtil.handleExperimentalFlagUsage;
+import static lombok.javac.Javac.CTC_EQUAL;
+import static lombok.javac.Javac.CTC_BOT;
 import static lombok.javac.handlers.JavacHandlerUtil.*;
 
 import java.lang.annotation.Annotation;
@@ -72,13 +74,8 @@
 import lombok.core.AnnotationValues;
 import lombok.core.HandlerPriority;
 import lombok.experimental.Delegate;
-import lombok.javac.FindTypeVarScanner;
-import lombok.javac.JavacAnnotationHandler;
-import lombok.javac.JavacNode;
-import lombok.javac.JavacResolution;
+import lombok.javac.*;
 import lombok.javac.JavacResolution.TypeNotConvertibleException;
-import lombok.javac.JavacTreeMaker;
-import lombok.javac.ResolutionResetNeeded;
 import lombok.permit.Permit;
 import lombok.spi.Provides;
 
@@ -111,7 +108,7 @@ public class HandleDelegate extends JavacAnnotationHandler<Delegate> {
 
 		@SuppressWarnings("deprecation") Class<? extends Annotation> oldDelegate = lombok.Delegate.class;
 		deleteAnnotationIfNeccessary(annotationNode, Delegate.class, oldDelegate);
-		
+
 		Type delegateType;
 		Name delegateName = annotationNode.toName(annotationNode.up().getName());
 		DelegateReceiver delegateReceiver;
@@ -211,16 +208,16 @@ public class HandleDelegate extends JavacAnnotationHandler<Delegate> {
 				}
 			}
 
-			for (MethodSig sig : signaturesToDelegate) generateAndAdd(sig, annotationNode, delegateName, delegateReceiver);
+			for (MethodSig sig : signaturesToDelegate) generateAndAdd(sig, annotationNode, delegateName, delegateReceiver, annotation.getInstance().skipAndReturnNullOnNullRef());
 		} catch (DelegateRecursion e) {
 			annotationNode.addError(String.format(RECURSION_NOT_ALLOWED, e.member, e.type));
 		}
 	}
 
-	public void generateAndAdd(MethodSig sig, JavacNode annotation, Name delegateName, DelegateReceiver delegateReceiver) {
+	public void generateAndAdd(MethodSig sig, JavacNode annotation, Name delegateName, DelegateReceiver delegateReceiver, boolean tryToAvoidNOE) {
 		List<JCMethodDecl> toAdd = new ArrayList<JCMethodDecl>();
 		try {
-			toAdd.add(createDelegateMethod(sig, annotation, delegateName, delegateReceiver));
+			toAdd.add(createDelegateMethod(sig, annotation, delegateName, delegateReceiver, tryToAvoidNOE));
 		} catch (TypeNotConvertibleException e) {
 			annotation.addError("Can't create delegate method for " + sig.name + ": " + e.getMessage());
 			return;
@@ -285,7 +282,7 @@ public void checkConflictOfTypeVarNames(MethodSig sig, JavacNode annotation) thr
 		}
 	}
 
-	public JCMethodDecl createDelegateMethod(MethodSig sig, JavacNode annotation, Name delegateName, DelegateReceiver delegateReceiver) throws TypeNotConvertibleException, CantMakeDelegates {
+	public JCMethodDecl createDelegateMethod(MethodSig sig, JavacNode annotation, Name delegateName, DelegateReceiver delegateReceiver, boolean tryToAvoidNOE) throws TypeNotConvertibleException, CantMakeDelegates {
 		/* public <T, U, ...> ReturnType methodName(ParamType1 name1, ParamType2 name2, ...) throws T1, T2, ... {
 		 *      (return) delegate.<T, U>methodName(name1, name2);
 		 *  }
@@ -346,7 +343,18 @@ public JCMethodDecl createDelegateMethod(MethodSig sig, JavacNode annotation, Na
 
 		JCExpression delegateCall = maker.Apply(toList(typeArgs), maker.Select(delegateReceiver.get(annotation, delegateName), sig.name), toList(args));
 		JCStatement body = useReturn ? maker.Return(delegateCall) : maker.Exec(delegateCall);
-		JCBlock bodyBlock = maker.Block(0, com.sun.tools.javac.util.List.of(body));
+		JCBlock bodyBlock = null;
+		// only worked when avoid NPE been told and target method not return primitive type
+		if (tryToAvoidNOE && !Javac.isPrimitive(returnType)){
+			bodyBlock = maker.Block(0, com.sun.tools.javac.util.List.of(
+					maker.If(maker.Binary(CTC_EQUAL, delegateReceiver.get(annotation, delegateName), maker.Literal(CTC_BOT, null))
+							, maker.Return(useReturn ? maker.Literal(CTC_BOT, null) : null)
+							, null
+					)
+					, body));
+		}else{
+			bodyBlock = maker.Block(0, com.sun.tools.javac.util.List.of(body));
+		}
 
 		return recursiveSetGeneratedBy(maker.MethodDef(mods, sig.name, returnType, toList(typeParams), toList(params), toList(thrown), bodyBlock, null), annotation);
 	}