import java.util.List;

import org.mapstruct.Condition;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.factory.Mappers;

@Mapper
interface WrongConditionMapper {

    @Mapping(target = "currentId", source = "source.uuid")
    @Mapping(target = "targetIds", source = "sourceIds")
    Target map(Source source, List<String> sourceIds);

    @Condition
    default boolean isNotEmpty(List<String> elements) {
        return elements != null && !elements.isEmpty();
    }

    class Source {
        public String uuid;
    }

    class Target {
        public String currentId;
        public List<String> targetIds;
    }

}

class WrongConditionMapperImpl implements WrongConditionMapper {

    @Override
    public Target map(Source source, List<String> sourceIds) {
        if ( source == null && sourceIds == null ) {
            return null;
        }

        Target target = new Target();

        if ( source != null ) {
            // this isNotEmpty check has nothing to do with source.uuid or target.currentId
            if ( isNotEmpty( sourceIds ) ) {
                target.currentId = source.uuid;
            }
        }
        if ( isNotEmpty( sourceIds ) ) {
            List<String> list = sourceIds;
            target.targetIds = new ArrayList<String>( list );
        }

        return target;
    }
}

import java.util.List;

import org.mapstruct.Condition;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.factory.Mappers;

@Mapper
interface WrongConditionMapper {

    @Mapping(target = "currentId", source = "source.uuid")
    @Mapping(target = "targetIds", source = "sourceIds")
    Target map(Source source, List<String> sourceIds);

    @Condition
    default boolean isNotEmpty(List<String> elements) {
        return elements != null && !elements.isEmpty();
    }

    @Condition
    default boolean stringCondition(String str) {
        return str != null;
    }

    class Source {
        public String uuid;
    }

    class Target {
        public String currentId;
        public List<String> targetIds;
    }

}

import java.util.ArrayList;

import org.mapstruct.ap.testutil.IssueKey;
import org.mapstruct.ap.testutil.ProcessorTest;
import org.mapstruct.ap.testutil.WithClasses;
import org.mapstruct.factory.Mappers;

import static org.assertj.core.api.Assertions.assertThat;

@WithClasses(WrongConditionMapper.class)
@IssueKey("3601")
class Issue3601Test {

    @ProcessorTest
    void shouldMapCurrentId() {

        Issue3601Mapper mapper = Mappers.getMapper( Issue3601Mapper.class );
        Issue3601Mapper.Source source = new Issue3601Mapper.Source();
        source.uuid = "some-uuid";

        Issue3601Mapper.Target target = mapper.map( source, null );

        assertThat( target ).isNotNull();
        assertThat( target.currentId ).isEqualTo( "some-uuid" );
        assertThat( target.targetIds ).isNull();

        target = mapper.map( source, Collections.emptyList() );

        assertThat( target ).isNotNull();
        assertThat( target.currentId ).isEqualTo( "some-uuid" );
        assertThat( target.targetIds ).isNull();

        ArrayList<String> sourceIds = new ArrayList<>();
        sourceIds.add( "other-uuid" );
        target = mapper.map( source, sourceIds );

        assertThat( target ).isNotNull();
        assertThat( target.currentId ).isEqualTo( "some-uuid" );
        assertThat( target.targetIds ).containsExactly( "other-uuid" );
    }
}