SubclassExhaustiveStrategy.RUNTIME_EXCEPTION option does not work if the superclass has a non-empty constructor

[prtnv]

• Is this an issue (and hence not a question)?

If the superclass has a non-empty constructor, then MapStruct ignores the subclassExhaustiveStrategy = SubclassExhaustiveStrategy.RUNTIME_EXCEPTION option when generating code

MapStruct 1.5.1.Final, JDK 17

Reproduction scenario:

  @BeanMapping( subclassExhaustiveStrategy = SubclassExhaustiveStrategy.RUNTIME_EXCEPTION )
  @SubclassMapping( source = Source1.class, target = Target1.class )
  @SubclassMapping( source = Source2.class, target = Target2.class )
  AbstractTarget map( AbstractSource source );

  abstract class AbstractTarget {
    private final String name;

    protected AbstractTarget(String name) {
      this.name = name;
    }
    // getter
  }

  class Target1 extends AbstractTarget {
    protected Target1(String name) {
      super(name);
    }
  }

  class Target2 extends AbstractTarget {
    protected Target2(String name) {
      super(name);
    }
  }

  abstract class AbstractSource {
    private final String name;

    protected AbstractSource(String name) {
      this.name = name;
    }
    // getter
  }

  class Source1 extends AbstractSource {
    protected Source1(String name) {
      super(name);
    }
  }

  class Source2 extends AbstractSource {
    protected Source2(String name) {
      super(name);
    }
  }

For this example MapStruct generates the following code

@Override
public AbstractTarget map(AbstractSource source) {
    if ( source == null ) {
        return null;
    }
    if (source instanceof Source1) {
        return source1ToTarget1( (Source1) source );
    }
    else if (source instanceof Source2) {
        return source2ToTarget2( (Source2) source );
    }
    else {
        String name = null;
        name = source.getName();
        AbstractTarget abstractTarget = new AbstractTarget( name );
        return abstractTarget;
    }
}

I was expecting a new IllegalArgumentException to be thrown in the last else statement. And also this generated code doesn't compile due to new AbstractTarget( name )

After some debugging, I think that if change the isAbstractReturnType method in the BeanMappingMethod#isAbstractReturnType class from

public boolean isAbstractReturnType() {
    return getFactoryMethod() == null && !hasConstructorMappings() && returnTypeToConstruct != null
        && returnTypeToConstruct.isAbstract();
}

to

public boolean isAbstractReturnType() {
    return getFactoryMethod() == null ^ hasConstructorMappings() && returnTypeToConstruct != null
        && returnTypeToConstruct.isAbstract();
}

then everything will be fine

Can I try to create PR to fix it?

[antonvovk]

Hi!
@prtnv I can confirm that I am experiencing exactly the same problem. Thanks for creating an issue.