#61 Instantiating collections/maps also if implementation type is used as target type

processor/src/main/java/org/mapstruct/ap/model/Type.java

@@ -50,6 +50,7 @@ public class Type extends AbstractModelElement implements Comparable<Type> {
     private final boolean isInterface;
     private final boolean isEnumType;
     private final boolean isIterableType;
+    private final boolean isCollectionType;
     private final boolean isMapType;
     private final Type implementationType;
     private final TypeMirror typeMirror;
@@ -57,12 +58,12 @@ public class Type extends AbstractModelElement implements Comparable<Type> {
     private final TypeElement typeElement;
 
     public Type(TypeMirror typeMirror, List<Type> typeParameters, Type implementationType, boolean isIterableType,
-                boolean isMapType,
+                boolean isCollectionType, boolean isMapType, Types typeUtils, Elements elementUtils) {
-                Types typeUtils, Elements elementUtils) {
         this.typeMirror = typeMirror;
         this.implementationType = implementationType;
         this.typeParameters = typeParameters;
         this.isIterableType = isIterableType;
+        this.isCollectionType = isCollectionType;
         this.isMapType = isMapType;
         this.typeUtils = typeUtils;
 
@@ -134,6 +135,10 @@ public class Type extends AbstractModelElement implements Comparable<Type> {
         return isIterableType;
     }
 
+    public boolean isCollectionType() {
+        return isCollectionType;
+    }
+
     public boolean isMapType() {
         return isMapType;
     }

processor/src/main/java/org/mapstruct/ap/util/TypeFactory.java

@@ -55,6 +55,7 @@ public class TypeFactory {
     private final Types typeUtils;
 
     private final TypeMirror iterableType;
+    private final TypeMirror collectionType;
     private final TypeMirror mapType;
 
     private final Map<String, Type> implementationTypes = new HashMap<String, Type>();
@@ -64,6 +65,10 @@ public class TypeFactory {
         this.typeUtils = typeUtils;
 
         iterableType = typeUtils.erasure( elementUtils.getTypeElement( Iterable.class.getCanonicalName() ).asType() );
+        collectionType = typeUtils.erasure(
+            elementUtils.getTypeElement( Collection.class.getCanonicalName() )
+                .asType()
+        );
         mapType = typeUtils.erasure( elementUtils.getTypeElement( Map.class.getCanonicalName() ).asType() );
 
         implementationTypes.put( Iterable.class.getName(), getType( ArrayList.class ) );
@@ -101,6 +106,10 @@ public class TypeFactory {
             mirror,
             iterableType
         );
+        boolean isCollectionType = typeUtils.isSubtype(
+            mirror,
+            collectionType
+        );
         boolean isMapType = typeUtils.isSubtype(
             mirror,
             mapType
@@ -111,6 +120,7 @@ public class TypeFactory {
             getTypeParameters( mirror ),
             implementationType,
             isIterableType,
+            isCollectionType,
             isMapType,
             typeUtils,
             elementUtils
@@ -165,6 +175,7 @@ public class TypeFactory {
                 getTypeParameters( mirror ),
                 null,
                 implementationType.isIterableType(),
+                implementationType.isCollectionType(),
                 implementationType.isMapType(),
                 typeUtils,
                 elementUtils

processor/src/main/resources/org.mapstruct.ap.model.PropertyMapping.ftl

@@ -32,7 +32,7 @@
             </#if>
         <#-- c) simply set -->
         <#else>
-            <#if targetType.implementationType??>
+            <#if targetType.collectionType || targetType.mapType>
         if ( ${sourceBeanName}.${sourceAccessorName}() != null ) {
             ${ext.targetBeanName}.${targetAccessorName}( new <#if targetType.implementationType??><@includeModel object=targetType.implementationType/><#else><@includeModel object=targetType/></#if>( ${sourceBeanName}.${sourceAccessorName}() ) );
         }

processor/src/test/java/org/mapstruct/ap/test/collection/CollectionMappingTest.java

@@ -165,6 +165,18 @@ public class CollectionMappingTest extends MapperTestBase {
         assertThat( source.getStringSet() ).containsOnly( "Bob", "Alice" );
     }
 
+    @Test
+    @IssueKey("6")
+    public void shouldMapHashSetAsCopy() {
+        Source source = new Source();
+        source.setStringHashSet( new HashSet<String>( Arrays.asList( "Bob", "Alice" ) ) );
+
+        Target target = SourceTargetMapper.INSTANCE.sourceToTarget( source );
+        target.getStringHashSet().add( "Bill" );
+
+        assertThat( source.getStringHashSet() ).containsOnly( "Bob", "Alice" );
+    }
+
     @Test
     @IssueKey("6")
     public void shouldReverseMapSetAsCopy() {