#148, #1386, #2593 Only import top level classes

Instead of importing all classes, inner classes will be used through their top level classes only.
This also fixes the problem in #2593 since inner classes are no longer imported but used through their top classes

integrationtest/src/test/java/org/mapstruct/itest/tests/MavenIntegrationTest.java

@@ -128,6 +128,11 @@ public class MavenIntegrationTest {
     void simpleTest() {
     }
 
+    // for issue #2593
+    @ProcessorTest(baseDir = "defaultPackage")
+    void defaultPackageTest() {
+    }
+
     @ProcessorTest(baseDir = "springTest")
     void springTest() {
     }

integrationtest/src/test/resources/defaultPackage/main/java/DefaultPackageObject.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class DefaultPackageObject {
+    public enum CarType {
+        SEDAN, CAMPER, X4, TRUCK;
+    }
+
+    static public class Car {
+
+        private String make;
+        private int numberOfSeats;
+        private CarType type;
+
+        public Car(String string, int numberOfSeats, CarType sedan) {
+            this.make = string;
+            this.numberOfSeats = numberOfSeats;
+            this.type = sedan;
+        }
+
+
+        public String getMake() {
+            return make;
+        }
+
+        public void setMake(String make) {
+            this.make = make;
+        }
+
+        public int getNumberOfSeats() {
+            return numberOfSeats;
+        }
+
+        public void setNumberOfSeats(int numberOfSeats) {
+            this.numberOfSeats = numberOfSeats;
+        }
+
+        public CarType getType() {
+            return type;
+        }
+
+        public void setType(CarType type) {
+            this.type = type;
+        }
+    }
+
+    static public class CarDto {
+
+        private String make;
+        private int seatCount;
+        private String type;
+
+        public String getMake() {
+            return make;
+        }
+
+        public void setMake(String make) {
+            this.make = make;
+        }
+
+        public int getSeatCount() {
+            return seatCount;
+        }
+
+        public void setSeatCount(int seatCount) {
+            this.seatCount = seatCount;
+        }
+
+        public String getType() {
+            return type;
+        }
+
+        public void setType(String type) {
+            this.type = type;
+        }
+    }
+
+
+    @Mapper
+    public interface CarMapper {
+
+        CarMapper INSTANCE = Mappers.getMapper( CarMapper.class );
+
+        @Mapping(source = "numberOfSeats", target = "seatCount")
+        CarDto carToCarDto(Car car);
+    }
+}

integrationtest/src/test/resources/defaultPackage/pom.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Copyright MapStruct Authors.
+
+    Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>org.mapstruct</groupId>
+        <artifactId>mapstruct-it-parent</artifactId>
+        <version>1.0.0</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+
+    <artifactId>defaultPackage</artifactId>
+    <packaging>jar</packaging>
+</project>

integrationtest/src/test/resources/defaultPackage/test/java/DefaultPackageTest.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Filip Hrisafov
+ */
+
+public class DefaultPackageTest {
+
+    @Test
+    public void shouldWorkCorrectlyInDefaultPackage() {
+        DefaultPackageObject.CarDto carDto = DefaultPackageObject.CarMapper.INSTANCE.carToCarDto(
+            new DefaultPackageObject.Car(
+                "Morris",
+                5,
+                DefaultPackageObject.CarType.SEDAN
+            ) );
+
+        assertThat( carDto ).isNotNull();
+        assertThat( carDto.getMake() ).isEqualTo( "Morris" );
+        assertThat( carDto.getSeatCount() ).isEqualTo( 5 );
+        assertThat( carDto.getType() ).isEqualTo( "SEDAN" );
+    }
+}

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

@@ -5,9 +5,11 @@
  */
 package org.mapstruct.ap.internal.model.common;
 
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Deque;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -22,6 +24,7 @@ import javax.lang.model.element.Element;
 import javax.lang.model.element.ElementKind;
 import javax.lang.model.element.ExecutableElement;
 import javax.lang.model.element.Modifier;
+import javax.lang.model.element.NestingKind;
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.element.VariableElement;
 import javax.lang.model.type.ArrayType;
@@ -71,9 +74,11 @@ public class Type extends ModelElement implements Comparable<Type> {
 
     private final ImplementationType implementationType;
     private final Type componentType;
+    private final Type topLevelType;
 
     private final String packageName;
     private final String name;
+    private final String nameWithTopLevelTypeName;
     private final String qualifiedName;
 
     private final boolean isInterface;
@@ -172,6 +177,9 @@ public class Type extends ModelElement implements Comparable<Type> {
         this.filters = new Filters( accessorNaming, typeUtils, typeMirror );
 
         this.loggingVerbose = loggingVerbose;
+
+        this.topLevelType = topLevelType( this.typeElement, this.typeFactory );
+        this.nameWithTopLevelTypeName = nameWithTopLevelTypeName( this.typeElement );
     }
     //CHECKSTYLE:ON
 
@@ -199,11 +207,23 @@ public class Type extends ModelElement implements Comparable<Type> {
      * <p>
      * If the {@code java.time} variant is referred to first, the {@code java.time.LocalDateTime} will be imported
      * and the {@code org.joda} variant will be referred to with its FQN.
+     * <p>
+     * If the type is nested and its top level type is to be imported
+     * then the name including its top level type will be returned.
      *
-     * @return Just the name if this {@link Type} will be imported, otherwise the fully-qualified name.
+     * @return Just the name if this {@link Type} will be imported, the name up to the top level {@link Type}
+     * (if the top level type is important, otherwise the fully-qualified name.
      */
     public String createReferenceName() {
-        return isToBeImported() ? name :  ( shouldUseSimpleName() ? name : qualifiedName );
+        if ( isToBeImported() || shouldUseSimpleName() ) {
+            return name;
+        }
+
+        if ( isTopLevelTypeToBeImported() && nameWithTopLevelTypeName != null ) {
+            return nameWithTopLevelTypeName;
+        }
+
+        return qualifiedName;
     }
 
     public List<Type> getTypeParameters() {
@@ -402,6 +422,10 @@ public class Type extends ModelElement implements Comparable<Type> {
             result.addAll( componentType.getImportTypes() );
         }
 
+        if ( topLevelType != null ) {
+            result.addAll( topLevelType.getImportTypes() );
+        }
+
         for ( Type parameter : typeParameters ) {
             result.addAll( parameter.getImportTypes() );
         }
@@ -413,6 +437,10 @@ public class Type extends ModelElement implements Comparable<Type> {
         return result;
     }
 
+    protected boolean isTopLevelTypeToBeImported() {
+        return topLevelType != null && topLevelType.isToBeImported();
+    }
+
     /**
      * Whether this type is to be imported by means of an import statement in the currently generated source file
      * (it can be referenced in the generated source using its simple name) or not (referenced using the FQN).
@@ -435,7 +463,7 @@ public class Type extends ModelElement implements Comparable<Type> {
                     isToBeImported = true;
                 }
             }
-            else {
+            else if ( typeElement == null || !typeElement.getNestingKind().isNested() ) {
                 toBeImportedTypes.put( trimmedName, trimmedQualifiedName );
                 isToBeImported = true;
             }
@@ -1492,4 +1520,39 @@ public class Type extends ModelElement implements Comparable<Type> {
         return trimmedClassName;
     }
 
+    private static String nameWithTopLevelTypeName(TypeElement element) {
+        if ( element == null ) {
+            return null;
+        }
+        if ( !element.getNestingKind().isNested() ) {
+            return element.getSimpleName().toString();
+        }
+
+        Deque<CharSequence> elements = new ArrayDeque<>();
+        elements.addFirst( element.getSimpleName() );
+        Element parent = element.getEnclosingElement();
+        while ( parent != null && parent.getKind() != ElementKind.PACKAGE ) {
+            elements.addFirst( parent.getSimpleName() );
+            parent = parent.getEnclosingElement();
+        }
+
+        return String.join( ".", elements );
+    }
+
+    private static Type topLevelType(TypeElement typeElement, TypeFactory typeFactory) {
+        if ( typeElement == null || typeElement.getNestingKind() == NestingKind.TOP_LEVEL ) {
+            return null;
+        }
+
+        Element parent = typeElement.getEnclosingElement();
+        while ( parent != null ) {
+            if ( parent.getEnclosingElement() != null &&
+                parent.getEnclosingElement().getKind() == ElementKind.PACKAGE ) {
+                break;
+            }
+            parent = parent.getEnclosingElement();
+        }
+        return parent == null ? null : typeFactory.getType( parent.asType() );
+    }
+
 }

processor/src/test/java/org/mapstruct/ap/test/imports/InnerClassesImportsTest.java

@@ -14,7 +14,6 @@ import org.mapstruct.ap.test.imports.innerclasses.InnerClassMapper;
 import org.mapstruct.ap.test.imports.innerclasses.SourceWithInnerClass;
 import org.mapstruct.ap.test.imports.innerclasses.SourceWithInnerClass.SourceInnerClass;
 import org.mapstruct.ap.test.imports.innerclasses.TargetWithInnerClass;
-import org.mapstruct.ap.test.imports.innerclasses.TargetWithInnerClass.TargetInnerClass;
 import org.mapstruct.ap.test.imports.innerclasses.TargetWithInnerClass.TargetInnerClass.TargetInnerInnerClass;
 import org.mapstruct.ap.testutil.IssueKey;
 import org.mapstruct.ap.testutil.ProcessorTest;
@@ -47,8 +46,7 @@ public class InnerClassesImportsTest {
 
         assertThat( target ).isNotNull();
         assertThat( target.getInnerClassMember().getValue() ).isEqualTo( 412 );
-        generatedSource.forMapper( InnerClassMapper.class ).containsImportFor( SourceInnerClass.class );
-        generatedSource.forMapper( InnerClassMapper.class ).containsImportFor( TargetInnerClass.class );
+        generatedSource.addComparisonToFixtureFor( InnerClassMapper.class );
     }
 
     @ProcessorTest
@@ -61,8 +59,7 @@ public class InnerClassesImportsTest {
 
         assertThat( target ).isNotNull();
         assertThat( target.getValue() ).isEqualTo( 412 );
-        generatedSource.forMapper( InnerClassMapper.class ).containsImportFor( SourceInnerClass.class );
-        generatedSource.forMapper( InnerClassMapper.class ).containsImportFor( TargetInnerInnerClass.class );
+        generatedSource.addComparisonToFixtureFor( InnerClassMapper.class );
     }
 
     @ProcessorTest
@@ -82,6 +79,6 @@ public class InnerClassesImportsTest {
         assertThat( sourceAgain ).isNotNull();
         assertThat( sourceAgain.getInnerEnum() ).isEqualTo( InnerEnum.A );
 
-        generatedSource.forMapper( BeanWithInnerEnumMapper.class ).containsImportFor( InnerEnum.class );
+        generatedSource.addComparisonToFixtureFor( BeanWithInnerEnumMapper.class );
     }
 }

processor/src/test/java/org/mapstruct/ap/test/imports/nested/NestedImportsTest.java

@@ -0,0 +1,54 @@
+/*
+ * 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.imports.nested;
+
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.mapstruct.ap.test.imports.nested.other.SourceInOtherPackage;
+import org.mapstruct.ap.test.imports.nested.other.TargetInOtherPackage;
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.ProcessorTest;
+import org.mapstruct.ap.testutil.WithClasses;
+import org.mapstruct.ap.testutil.runner.GeneratedSource;
+
+/**
+ * @author Filip Hrisafov
+ */
+@WithClasses({
+    SourceInOtherPackage.class,
+    TargetInOtherPackage.class,
+    Source.class,
+    Target.class
+})
+@IssueKey("1386,148")
+class NestedImportsTest {
+
+    @RegisterExtension
+    final GeneratedSource generatedSource = new GeneratedSource();
+
+    @ProcessorTest
+    @WithClasses( {
+        SourceInOtherPackageMapper.class
+    } )
+    void shouldGenerateNestedInnerClassesForSourceInOtherPackage() {
+        generatedSource.addComparisonToFixtureFor( SourceInOtherPackageMapper.class );
+    }
+
+    @ProcessorTest
+    @WithClasses( {
+        NestedSourceInOtherPackageMapper.class
+    } )
+    void shouldGenerateCorrectImportsForTopLevelClassesFromOnlyNestedInnerClasses() {
+        generatedSource.addComparisonToFixtureFor( NestedSourceInOtherPackageMapper.class );
+    }
+
+    @ProcessorTest
+    @WithClasses( {
+        TargetInOtherPackageMapper.class
+    } )
+    void shouldGenerateNestedInnerClassesForTargetInOtherPackage() {
+        generatedSource.addComparisonToFixtureFor( TargetInOtherPackageMapper.class );
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/imports/nested/NestedSourceInOtherPackageMapper.java

@@ -0,0 +1,18 @@
+/*
+ * 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.imports.nested;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.ap.test.imports.nested.other.SourceInOtherPackage;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface NestedSourceInOtherPackageMapper {
+
+    Target.Nested map(SourceInOtherPackage.Nested source);
+}

processor/src/test/java/org/mapstruct/ap/test/imports/nested/Source.java

@@ -0,0 +1,48 @@
+/*
+ * 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.imports.nested;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class Source {
+
+    private Nested value;
+
+    public Nested getValue() {
+        return value;
+    }
+
+    public void setValue(Nested value) {
+        this.value = value;
+    }
+
+    public static class Nested {
+
+        private Inner inner;
+
+        public static class Inner {
+
+            private String value;
+
+            public String getValue() {
+                return value;
+            }
+
+            public void setValue(String value) {
+                this.value = value;
+            }
+        }
+
+        public Inner getInner() {
+            return inner;
+        }
+
+        public void setInner(Inner inner) {
+            this.inner = inner;
+        }
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/imports/nested/SourceInOtherPackageMapper.java

@@ -0,0 +1,18 @@
+/*
+ * 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.imports.nested;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.ap.test.imports.nested.other.SourceInOtherPackage;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface SourceInOtherPackageMapper {
+
+    Target map(SourceInOtherPackage source);
+}

processor/src/test/java/org/mapstruct/ap/test/imports/nested/Target.java

@@ -0,0 +1,48 @@
+/*
+ * 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.imports.nested;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class Target {
+
+    private Nested value;
+
+    public Nested getValue() {
+        return value;
+    }
+
+    public void setValue(Nested value) {
+        this.value = value;
+    }
+
+    public static class Nested {
+
+        private Inner inner;
+
+        public static class Inner {
+
+            private String value;
+
+            public String getValue() {
+                return value;
+            }
+
+            public void setValue(String value) {
+                this.value = value;
+            }
+        }
+
+        public Inner getInner() {
+            return inner;
+        }
+
+        public void setInner(Inner inner) {
+            this.inner = inner;
+        }
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/imports/nested/TargetInOtherPackageMapper.java

@@ -0,0 +1,18 @@
+/*
+ * 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.imports.nested;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.ap.test.imports.nested.other.TargetInOtherPackage;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface TargetInOtherPackageMapper {
+
+    TargetInOtherPackage map(Source source);
+}

processor/src/test/java/org/mapstruct/ap/test/imports/nested/other/SourceInOtherPackage.java

@@ -0,0 +1,48 @@
+/*
+ * 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.imports.nested.other;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class SourceInOtherPackage {
+
+    private Nested value;
+
+    public Nested getValue() {
+        return value;
+    }
+
+    public void setValue(Nested value) {
+        this.value = value;
+    }
+
+    public static class Nested {
+
+        private Inner inner;
+
+        public static class Inner {
+
+            private String value;
+
+            public String getValue() {
+                return value;
+            }
+
+            public void setValue(String value) {
+                this.value = value;
+            }
+        }
+
+        public Inner getInner() {
+            return inner;
+        }
+
+        public void setInner(Inner inner) {
+            this.inner = inner;
+        }
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/imports/nested/other/TargetInOtherPackage.java

@@ -0,0 +1,48 @@
+/*
+ * 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.imports.nested.other;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class TargetInOtherPackage {
+
+    private Nested value;
+
+    public Nested getValue() {
+        return value;
+    }
+
+    public void setValue(Nested value) {
+        this.value = value;
+    }
+
+    public static class Nested {
+
+        private Inner inner;
+
+        public static class Inner {
+
+            private String value;
+
+            public String getValue() {
+                return value;
+            }
+
+            public void setValue(String value) {
+                this.value = value;
+            }
+        }
+
+        public Inner getInner() {
+            return inner;
+        }
+
+        public void setInner(Inner inner) {
+            this.inner = inner;
+        }
+    }
+}

processor/src/test/resources/fixtures/org/mapstruct/ap/test/imports/innerclasses/BeanWithInnerEnumMapperImpl.java

@@ -0,0 +1,48 @@
+/*
+ * 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.imports.innerclasses;
+
+import javax.annotation.processing.Generated;
+
+@Generated(
+    value = "org.mapstruct.ap.MappingProcessor",
+    date = "2021-10-16T21:06:53+0200",
+    comments = "version: , compiler: javac, environment: Java 17 (Oracle Corporation)"
+)
+public class BeanWithInnerEnumMapperImpl implements BeanWithInnerEnumMapper {
+
+    @Override
+    public BeanWithInnerEnum fromFacade(BeanFacade beanFacade) {
+        if ( beanFacade == null ) {
+            return null;
+        }
+
+        BeanWithInnerEnum beanWithInnerEnum = new BeanWithInnerEnum();
+
+        beanWithInnerEnum.setTest( beanFacade.getTest() );
+        if ( beanFacade.getInnerEnum() != null ) {
+            beanWithInnerEnum.setInnerEnum( Enum.valueOf( BeanWithInnerEnum.InnerEnum.class, beanFacade.getInnerEnum() ) );
+        }
+
+        return beanWithInnerEnum;
+    }
+
+    @Override
+    public BeanFacade toFacade(BeanWithInnerEnum beanWithInnerEnum) {
+        if ( beanWithInnerEnum == null ) {
+            return null;
+        }
+
+        BeanFacade beanFacade = new BeanFacade();
+
+        beanFacade.setTest( beanWithInnerEnum.getTest() );
+        if ( beanWithInnerEnum.getInnerEnum() != null ) {
+            beanFacade.setInnerEnum( beanWithInnerEnum.getInnerEnum().name() );
+        }
+
+        return beanFacade;
+    }
+}

processor/src/test/resources/fixtures/org/mapstruct/ap/test/imports/innerclasses/InnerClassMapperImpl.java

@@ -0,0 +1,55 @@
+/*
+ * 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.imports.innerclasses;
+
+import javax.annotation.processing.Generated;
+
+@Generated(
+    value = "org.mapstruct.ap.MappingProcessor",
+    date = "2021-10-16T21:06:53+0200",
+    comments = "version: , compiler: javac, environment: Java 17 (Oracle Corporation)"
+)
+public class InnerClassMapperImpl implements InnerClassMapper {
+
+    @Override
+    public TargetWithInnerClass sourceToTarget(SourceWithInnerClass source) {
+        if ( source == null ) {
+            return null;
+        }
+
+        TargetWithInnerClass targetWithInnerClass = new TargetWithInnerClass();
+
+        targetWithInnerClass.setInnerClassMember( innerSourceToInnerTarget( source.getInnerClassMember() ) );
+
+        return targetWithInnerClass;
+    }
+
+    @Override
+    public TargetWithInnerClass.TargetInnerClass innerSourceToInnerTarget(SourceWithInnerClass.SourceInnerClass source) {
+        if ( source == null ) {
+            return null;
+        }
+
+        TargetWithInnerClass.TargetInnerClass targetInnerClass = new TargetWithInnerClass.TargetInnerClass();
+
+        targetInnerClass.setValue( source.getValue() );
+
+        return targetInnerClass;
+    }
+
+    @Override
+    public TargetWithInnerClass.TargetInnerClass.TargetInnerInnerClass innerSourceToInnerInnerTarget(SourceWithInnerClass.SourceInnerClass source) {
+        if ( source == null ) {
+            return null;
+        }
+
+        TargetWithInnerClass.TargetInnerClass.TargetInnerInnerClass targetInnerInnerClass = new TargetWithInnerClass.TargetInnerClass.TargetInnerInnerClass();
+
+        targetInnerInnerClass.setValue( source.getValue() );
+
+        return targetInnerInnerClass;
+    }
+}

processor/src/test/resources/fixtures/org/mapstruct/ap/test/imports/nested/NestedSourceInOtherPackageMapperImpl.java

@@ -0,0 +1,42 @@
+/*
+ * 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.imports.nested;
+
+import javax.annotation.processing.Generated;
+import org.mapstruct.ap.test.imports.nested.other.SourceInOtherPackage;
+
+@Generated(
+    value = "org.mapstruct.ap.MappingProcessor",
+    date = "2021-10-24T19:26:14+0200",
+    comments = "version: , compiler: javac, environment: Java 1.8.0_161 (Oracle Corporation)"
+)
+public class NestedSourceInOtherPackageMapperImpl implements NestedSourceInOtherPackageMapper {
+
+    @Override
+    public Target.Nested map(SourceInOtherPackage.Nested source) {
+        if ( source == null ) {
+            return null;
+        }
+
+        Target.Nested nested = new Target.Nested();
+
+        nested.setInner( innerToInner( source.getInner() ) );
+
+        return nested;
+    }
+
+    protected Target.Nested.Inner innerToInner(SourceInOtherPackage.Nested.Inner inner) {
+        if ( inner == null ) {
+            return null;
+        }
+
+        Target.Nested.Inner inner1 = new Target.Nested.Inner();
+
+        inner1.setValue( inner.getValue() );
+
+        return inner1;
+    }
+}

processor/src/test/resources/fixtures/org/mapstruct/ap/test/imports/nested/SourceInOtherPackageMapperImpl.java

@@ -0,0 +1,54 @@
+/*
+ * 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.imports.nested;
+
+import javax.annotation.Generated;
+import org.mapstruct.ap.test.imports.nested.other.SourceInOtherPackage;
+
+@Generated(
+    value = "org.mapstruct.ap.MappingProcessor",
+    date = "2018-08-19T19:13:35+0200",
+    comments = "version: , compiler: javac, environment: Java 1.8.0_161 (Oracle Corporation)"
+)
+public class SourceInOtherPackageMapperImpl implements SourceInOtherPackageMapper {
+
+    @Override
+    public Target map(SourceInOtherPackage source) {
+        if ( source == null ) {
+            return null;
+        }
+
+        Target target = new Target();
+
+        target.setValue( nestedToNested( source.getValue() ) );
+
+        return target;
+    }
+
+    protected Target.Nested.Inner innerToInner(SourceInOtherPackage.Nested.Inner inner) {
+        if ( inner == null ) {
+            return null;
+        }
+
+        Target.Nested.Inner inner1 = new Target.Nested.Inner();
+
+        inner1.setValue( inner.getValue() );
+
+        return inner1;
+    }
+
+    protected Target.Nested nestedToNested(SourceInOtherPackage.Nested nested) {
+        if ( nested == null ) {
+            return null;
+        }
+
+        Target.Nested nested1 = new Target.Nested();
+
+        nested1.setInner( innerToInner( nested.getInner() ) );
+
+        return nested1;
+    }
+}

processor/src/test/resources/fixtures/org/mapstruct/ap/test/imports/nested/TargetInOtherPackageMapperImpl.java

@@ -0,0 +1,54 @@
+/*
+ * 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.imports.nested;
+
+import javax.annotation.processing.Generated;
+import org.mapstruct.ap.test.imports.nested.other.TargetInOtherPackage;
+
+@Generated(
+    value = "org.mapstruct.ap.MappingProcessor",
+    date = "2021-10-24T13:45:02+0200",
+    comments = "version: , compiler: javac, environment: Java 1.8.0_161 (Oracle Corporation)"
+)
+public class TargetInOtherPackageMapperImpl implements TargetInOtherPackageMapper {
+
+    @Override
+    public TargetInOtherPackage map(Source source) {
+        if ( source == null ) {
+            return null;
+        }
+
+        TargetInOtherPackage targetInOtherPackage = new TargetInOtherPackage();
+
+        targetInOtherPackage.setValue( nestedToNested( source.getValue() ) );
+
+        return targetInOtherPackage;
+    }
+
+    protected TargetInOtherPackage.Nested.Inner innerToInner(Source.Nested.Inner inner) {
+        if ( inner == null ) {
+            return null;
+        }
+
+        TargetInOtherPackage.Nested.Inner inner1 = new TargetInOtherPackage.Nested.Inner();
+
+        inner1.setValue( inner.getValue() );
+
+        return inner1;
+    }
+
+    protected TargetInOtherPackage.Nested nestedToNested(Source.Nested nested) {
+        if ( nested == null ) {
+            return null;
+        }
+
+        TargetInOtherPackage.Nested nested1 = new TargetInOtherPackage.Nested();
+
+        nested1.setInner( innerToInner( nested.getInner() ) );
+
+        return nested1;
+    }
+}