#782 Adding negative test for @MappingTarget with immutable classes

processor/src/main/java/org/mapstruct/ap/internal/processor/MethodRetrievalProcessor.java

@@ -403,6 +403,11 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
             return false;
         }
 
+        if ( targetParameter != null && targetParameter.getType().getBuilderType() != null  ) {
+            messager.printMessage( method, Message.RETRIEVAL_IMMUTABLE_TARGET );
+            return false;
+        }
+
         if ( isVoid( resultType ) ) {
             messager.printMessage( method, Message.RETRIEVAL_VOID_MAPPING_METHOD );
             return false;

processor/src/main/java/org/mapstruct/ap/internal/util/Message.java

@@ -100,6 +100,7 @@ public enum Message {
 
     RETRIEVAL_NO_INPUT_ARGS( "Can't generate mapping method with no input arguments." ),
     RETRIEVAL_DUPLICATE_MAPPING_TARGETS( "Can't generate mapping method with more than one @MappingTarget parameter." ),
+    RETRIEVAL_IMMUTABLE_TARGET( "Can't generate mapping method when @MappingTarget is supposed to be immutable (has a builder)." ),
     RETRIEVAL_VOID_MAPPING_METHOD( "Can't generate mapping method with return type void." ),
     RETRIEVAL_NON_ASSIGNABLE_RESULTTYPE( "The result type is not assignable to the the return type." ),
     RETRIEVAL_ITERABLE_TO_NON_ITERABLE( "Can't generate mapping method from iterable type to non-iterable type." ),

processor/src/test/java/org/mapstruct/ap/test/builder/abstractBuilder/AbstractBuilderTest.java

@@ -30,7 +30,6 @@ import static org.assertj.core.api.Assertions.assertThat;
  * builder class, and some of the properties are written by the concrete builder implementation.
  */
 @WithClasses({
-    Product.class,
     AbstractProductBuilder.class,
     AbstractImmutableProduct.class,
     ImmutableProduct.class,

processor/src/test/java/org/mapstruct/ap/test/builder/abstractBuilder/AbstractImmutableProduct.java

@@ -21,7 +21,7 @@ package org.mapstruct.ap.test.builder.abstractBuilder;
 /**
  * @author Filip Hrisafov
  */
-public abstract class AbstractImmutableProduct implements Product {
+public abstract class AbstractImmutableProduct {
 
     private final String name;
 

processor/src/test/java/org/mapstruct/ap/test/builder/abstractBuilder/AbstractProductBuilder.java

@@ -18,7 +18,7 @@
  */
 package org.mapstruct.ap.test.builder.abstractBuilder;
 
-public abstract class AbstractProductBuilder<T extends Product> {
+public abstract class AbstractProductBuilder<T extends AbstractImmutableProduct> {
 
     protected String name;
 

processor/src/test/java/org/mapstruct/ap/test/builder/abstractBuilder/ImmutableProduct.java

@@ -31,7 +31,6 @@ public class ImmutableProduct extends AbstractImmutableProduct {
         return new ImmutableProductBuilder();
     }
 
-    @Override
     public Integer getPrice() {
         return price;
     }

processor/src/test/java/org/mapstruct/ap/test/builder/abstractBuilder/Product.java

@@ -1,25 +0,0 @@
-/**
- *  Copyright 2012-2017 Gunnar Morling (http://www.gunnarmorling.de/)
- *  and/or other contributors as indicated by the @authors tag. See the
- *  copyright.txt file in the distribution for a full listing of all
- *  contributors.
- *
- *  Licensed 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 org.mapstruct.ap.test.builder.abstractBuilder;
-
-public interface Product {
-    String getName();
-
-    Integer getPrice();
-}

processor/src/test/java/org/mapstruct/ap/test/builder/mappingTarget/simple/BuilderInfoTargetTest.java

@@ -26,6 +26,9 @@ import org.mapstruct.ap.testutil.runner.AnnotationProcessorTestRunner;
 import org.mapstruct.ap.testutil.runner.GeneratedSource;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import org.mapstruct.ap.testutil.compilation.annotation.CompilationResult;
+import org.mapstruct.ap.testutil.compilation.annotation.Diagnostic;
+import org.mapstruct.ap.testutil.compilation.annotation.ExpectedCompilationOutcome;
 
 @WithClasses({
     SimpleMutableSource.class,
@@ -50,4 +53,18 @@ public class BuilderInfoTargetTest {
         assertThat( targetObject.getAge() ).isEqualTo( 3 );
         assertThat( targetObject.getName() ).isEqualTo( "Bob" );
     }
+
+    @WithClasses(ErroneousSimpleBuilderMapper.class)
+    @Test
+    @ExpectedCompilationOutcome(value = CompilationResult.FAILED,
+        diagnostics = {
+            @Diagnostic(type = ErroneousSimpleBuilderMapper.class,
+                kind = javax.tools.Diagnostic.Kind.ERROR,
+                line = 26,
+                messageRegExp = "^Can't generate mapping method when @MappingTarget is supposed to be immutable "
+                + "\\(has a builder\\)\\.$")
+        })
+    public void shouldFailCannotModifyImmutable() {
+
+    }
 }

processor/src/test/java/org/mapstruct/ap/test/builder/mappingTarget/simple/ErroneousSimpleBuilderMapper.java

@@ -19,8 +19,9 @@
 package org.mapstruct.ap.test.builder.mappingTarget.simple;
 
 import org.mapstruct.Mapper;
+import org.mapstruct.MappingTarget;
 
 @Mapper
-public interface InvalidSimpleBuilderMapper {
-    SimpleImmutableTarget toImmutable(SimpleMutableSource source);
+public interface ErroneousSimpleBuilderMapper {
+    void toImmutable(SimpleMutableSource source, @MappingTarget SimpleImmutableTarget target);
 }