#607 Mapping Iterable<?> object to an object instead of collection

documentation/src/main/asciidoc/chapter-6-mapping-collections.asciidoc

@@ -90,7 +90,7 @@ carDto.getPassengers().addAll( personsToPersonDtos( car.getPassengers() ) );
 
 [WARNING]
 ====
-It is not allowed to declare mapping methods with an iterable source and a non-iterable target or the other way around. An error will be raised when detecting this situation.
+It is not allowed to declare mapping methods with an iterable source (from a java package) and a non-iterable target or the other way around. An error will be raised when detecting this situation.
 ====
 
 [[mapping-maps]]
@@ -224,4 +224,4 @@ When an iterable or map mapping method declares an interface type as return type
 
 |`ConcurrentMap`|`ConcurrentHashMap`
 |`ConcurrentNavigableMap`|`ConcurrentSkipListMap`
-|===
+|===

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

@@ -483,7 +483,7 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
 
         Type parameterType = sourceParameters.get( 0 ).getType();
 
-        if ( parameterType.isIterableOrStreamType() && !resultType.isIterableOrStreamType() ) {
+        if ( isStreamTypeOrIterableFromJavaStdLib( parameterType ) && !resultType.isIterableOrStreamType() ) {
             messager.printMessage( method, Message.RETRIEVAL_ITERABLE_TO_NON_ITERABLE );
             return false;
         }
@@ -493,7 +493,7 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
             return false;
         }
 
-        if ( !parameterType.isIterableOrStreamType() && resultType.isIterableOrStreamType() ) {
+        if ( !parameterType.isIterableOrStreamType() && isStreamTypeOrIterableFromJavaStdLib( resultType ) ) {
             messager.printMessage( method, Message.RETRIEVAL_NON_ITERABLE_TO_ITERABLE );
             return false;
         }
@@ -534,6 +534,10 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
         return true;
     }
 
+    private boolean isStreamTypeOrIterableFromJavaStdLib(Type type) {
+        return type.isStreamType() || ( type.isIterableType() && type.isJavaLangType() );
+    }
+
     /**
      * Retrieves the mappings configured via {@code @Mapping} from the given
      * method.

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

@@ -143,9 +143,9 @@ public enum Message {
     RETRIEVAL_DUPLICATE_MAPPING_TARGETS( "Can't generate mapping method with more than one @MappingTarget parameter." ),
     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." ),
+    RETRIEVAL_ITERABLE_TO_NON_ITERABLE( "Can't generate mapping method from iterable type from java stdlib to non-iterable type." ),
     RETRIEVAL_MAPPING_HAS_TARGET_TYPE_PARAMETER( "Can't generate mapping method that has a parameter annotated with @TargetType." ),
-    RETRIEVAL_NON_ITERABLE_TO_ITERABLE( "Can't generate mapping method from non-iterable type to iterable type." ),
+    RETRIEVAL_NON_ITERABLE_TO_ITERABLE( "Can't generate mapping method from non-iterable type to iterable type from java stdlib." ),
     RETRIEVAL_PRIMITIVE_PARAMETER( "Can't generate mapping method with primitive parameter type." ),
     RETRIEVAL_PRIMITIVE_RETURN( "Can't generate mapping method with primitive return type." ),
     RETRIEVAL_TYPE_VAR_SOURCE( "Can't generate mapping method for a generic type variable source." ),

processor/src/test/java/org/mapstruct/ap/test/collection/erroneous/ErroneousCollectionMappingTest.java

@@ -28,21 +28,25 @@ public class ErroneousCollectionMappingTest {
 
     @Test
     @IssueKey("6")
-    @WithClasses({ ErroneousCollectionToNonCollectionMapper.class })
+    @WithClasses({ ErroneousCollectionToNonCollectionMapper.class, Source.class })
     @ExpectedCompilationOutcome(
         value = CompilationResult.FAILED,
         diagnostics = {
             @Diagnostic(type = ErroneousCollectionToNonCollectionMapper.class,
                 kind = Kind.ERROR,
                 line = 15,
-                message = "Can't generate mapping method from iterable type to non-iterable type."),
+                message = "Can't generate mapping method from iterable type from java stdlib to non-iterable type."),
             @Diagnostic(type = ErroneousCollectionToNonCollectionMapper.class,
                 kind = Kind.ERROR,
                 line = 17,
-                message = "Can't generate mapping method from non-iterable type to iterable type.")
+                message = "Can't generate mapping method from non-iterable type to iterable type from java stdlib."),
+            @Diagnostic(type = ErroneousCollectionToNonCollectionMapper.class,
+                kind = Kind.ERROR,
+                line = 19,
+                message = "Can't generate mapping method from non-iterable type to iterable type from java stdlib.")
         }
     )
-    public void shouldFailToGenerateImplementationBetweenCollectionAndNonCollection() {
+    public void shouldFailToGenerateImplementationBetweenCollectionAndNonCollectionWithResultTypeFromJava() {
     }
 
     @Test

processor/src/test/java/org/mapstruct/ap/test/collection/erroneous/ErroneousCollectionToNonCollectionMapper.java

@@ -15,4 +15,6 @@ public interface ErroneousCollectionToNonCollectionMapper {
     Integer stringSetToInteger(Set<String> strings);
 
     Set<String> integerToStringSet(Integer integer);
+
+    Set<String> nonJavaStdlibToCollection(Source stringCollection);
 }

processor/src/test/java/org/mapstruct/ap/test/collection/iterabletononiterable/Fruit.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.collection.iterabletononiterable;
+
+/**
+ *
+ * @author Saheb Preet Singh
+ */
+public class Fruit {
+
+    private String type;
+
+    public Fruit(String type) {
+        this.type = type;
+    }
+
+    public String getType() {
+        return type;
+    }
+
+    public void setType(String type) {
+        this.type = type;
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/collection/iterabletononiterable/FruitSalad.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.collection.iterabletononiterable;
+
+import java.util.List;
+
+/**
+ *
+ * @author Saheb Preet Singh
+ */
+public class FruitSalad {
+
+    private List<Fruit> fruits;
+
+    public FruitSalad(List<Fruit> fruits) {
+        this.fruits = fruits;
+    }
+
+    public List<Fruit> getFruits() {
+        return fruits;
+    }
+
+    public void setFruits(List<Fruit> fruits) {
+        this.fruits = fruits;
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/collection/iterabletononiterable/FruitsMapper.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.collection.iterabletononiterable;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.factory.Mappers;
+
+/**
+ *
+ * @author Saheb Preet Singh
+ */
+@Mapper
+public interface FruitsMapper {
+
+    FruitsMapper INSTANCE = Mappers.getMapper(
+        FruitsMapper.class );
+
+    FruitsMenu fruitSaladToMenu(FruitSalad salad);
+
+    FruitSalad fruitsMenuToSalad(FruitsMenu menu);
+}

processor/src/test/java/org/mapstruct/ap/test/collection/iterabletononiterable/FruitsMenu.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.collection.iterabletononiterable;
+
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ *
+ * @author Saheb Preet Singh
+ */
+public class FruitsMenu implements Iterable<Fruit> {
+
+    private List<Fruit> fruits;
+
+    public FruitsMenu(List<Fruit> fruits) {
+        this.fruits = fruits;
+    }
+
+    public List<Fruit> getFruits() {
+        return fruits;
+    }
+
+    public void setFruits(List<Fruit> fruits) {
+        this.fruits = fruits;
+    }
+
+    @Override
+    public Iterator<Fruit> iterator() {
+        return this.fruits.iterator();
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/collection/iterabletononiterable/IterableToNonIterableMappingTest.java

@@ -8,6 +8,7 @@ package org.mapstruct.ap.test.collection.iterabletononiterable;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import java.util.Arrays;
+import java.util.List;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -15,7 +16,8 @@ import org.mapstruct.ap.testutil.IssueKey;
 import org.mapstruct.ap.testutil.WithClasses;
 import org.mapstruct.ap.testutil.runner.AnnotationProcessorTestRunner;
 
-@WithClasses({ Source.class, Target.class, SourceTargetMapper.class, StringListMapper.class })
+@WithClasses({ Source.class, Target.class, SourceTargetMapper.class, StringListMapper.class, FruitsMenu.class,
+        FruitSalad.class, Fruit.class, FruitsMapper.class })
 @RunWith(AnnotationProcessorTestRunner.class)
 public class IterableToNonIterableMappingTest {
 
@@ -45,4 +47,26 @@ public class IterableToNonIterableMappingTest {
         assertThat( source.getNames() ).isEqualTo( Arrays.asList( "Alice", "Bob", "Jim" ) );
         assertThat( source.publicNames ).isEqualTo( Arrays.asList( "Alice", "Bob", "Jim" ) );
     }
+
+    @Test
+    @IssueKey("607")
+    public void shouldMapIterableToNonIterable() {
+        List<Fruit> fruits =  Arrays.asList( new Fruit( "mango" ), new Fruit( "apple" ),
+                new Fruit( "banana" ) );
+        FruitsMenu menu = new FruitsMenu(fruits);
+        FruitSalad salad = FruitsMapper.INSTANCE.fruitsMenuToSalad( menu );
+        assertThat( salad.getFruits().get( 0 ).getType() ).isEqualTo( "mango" );
+        assertThat( salad.getFruits().get( 1 ).getType() ).isEqualTo( "apple" );
+        assertThat( salad.getFruits().get( 2 ).getType() ).isEqualTo( "banana" );
+    }
+
+    @Test
+    @IssueKey("607")
+    public void shouldMapNonIterableToIterable() {
+        List<Fruit> fruits =  Arrays.asList( new Fruit( "mango" ), new Fruit( "apple" ),
+                new Fruit( "banana" ) );
+        FruitSalad salad = new FruitSalad(fruits);
+        FruitsMenu menu = FruitsMapper.INSTANCE.fruitSaladToMenu( salad );
+        assertThat( salad.getFruits() ).extracting( Fruit::getType ).containsExactly( "mango", "apple", "banana" );
+    }
 }

processor/src/test/java/org/mapstruct/ap/test/java8stream/erroneous/ErroneousStreamMappingTest.java

@@ -42,11 +42,11 @@ public class ErroneousStreamMappingTest {
             @Diagnostic(type = ErroneousStreamToNonStreamMapper.class,
                 kind = Kind.ERROR,
                 line = 15,
-                message = "Can't generate mapping method from iterable type to non-iterable type."),
+                message = "Can't generate mapping method from iterable type from java stdlib to non-iterable type."),
             @Diagnostic(type = ErroneousStreamToNonStreamMapper.class,
                 kind = Kind.ERROR,
                 line = 17,
-                message = "Can't generate mapping method from non-iterable type to iterable type.")
+                message = "Can't generate mapping method from non-iterable type to iterable type from java stdlib.")
         }
     )
     public void shouldFailToGenerateImplementationBetweenStreamAndNonStreamOrIterable() {