Embeddable with list inside repeated embedded is broken

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Consider the following JPA entities/embeddables:

@Entity
public class EntityA {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Extension(vendorName = "datanucleus", key = "gae.encoded-pk", value = "true")
    private String id;

    @Version
    private Integer version;

    @Embedded
    @Extension(vendorName = "datanucleus", key = "gae.unindexed", value = "true")
    private List<EmbeddableB> bs = new ArrayList<EmbeddableB>();

    public List<EmbeddableB> getBs() {
        return bs;
    }

    public void setBs(List<EmbeddableB> bs) {
        this.bs = bs;
    }
}

@Embeddable
public class EmbeddableB {

    @Basic
    @Extension(vendorName = "datanucleus", key = "gae.unindexed", value = "true")
    private int a;

    @Basic
    @Extension(vendorName = "datanucleus", key = "gae.unindexed", value = "true")
    private String b;

    @Basic
    @Extension(vendorName = "datanucleus", key = "gae.unindexed", value = "true")
    List<String> cs = new ArrayList<String>();

    @Embedded
    @Extension(vendorName = "datanucleus", key = "gae.unindexed", value = "true")
    EmbeddableC c = new EmbeddableC();

    public EmbeddableB(int a, String b) {
        this.a = a;
        this.b = b;
        cs.add("x");
    }

}

@Embeddable
public class EmbeddableC {

    @Basic
    private List<Integer> z = Arrays.asList(1, 2, 3);

}

The entity A contains a list of embeddables Bs that contain an embeddable C 
which contains a list.

Now run this code:

EntityManager em = EMF.get().createEntityManager();
try {
    EntityA a = new EntityA();
    a.getBs().add(new EmbeddableB(1, "Hello"));
    a.getBs().add(new EmbeddableB(2, "World"));
    em.persist(a);
} finally {
    em.close();
}

We are adding too Bs to an A so that A should contain two lists z coming from 
the embedded grandchild C. However, the datastore viewer shows columns a.0, 
b.0, a.1, b.1 as expected but only one column z (and not two columns z.0, z.1).

This looks like an error.

(Further, I have to annotate each property of the embedded classes to have them 
unindexed. It doesn't suffice to add this annotation just to the property "bs" 
of EntityA. This makes not generating indexes rather tedious. But it is 
important as soon as the number of generated columns becomes large — and 
indexing these columns may even make no sense in the first place.)

Original issue reported on code.google.com by marc.nieper@gmail.com on 17 Apr 2013 at 8:08