Cannot add items to nullable array

[cromoteca]

Describe the bug

This issue comes from https://vaadin.com/forum/t/nested-form-issue-typeerror-cannot-read-properties-of-undefined-reading-0/168014. The post contents are copied below.

I trying to use it for simple invoicing application (one invoice can have multiple invoice rows)

When I click on the “Add button”, then I get following error: TypeError: Cannot read properties of undefined (reading '0') at _BinderNode.initializeValue (.

Expected-behavior

No response

Reproduction

The react component looks like this:

function InvoiceItemForm({model, remove}: { model: InvoiceItemModel, remove: () => void }) {
    const {field} = useFormPart(model);

    return (
        <div>
            <NumberField {...field(model.quantity)} />
            <Button onClick={remove}>Remove</Button>
        </div>
    );
}

export default function GroupFormView() {
    const { field, model } = useForm(TransactionModel);
    const { items, value, setValue } = useFormArrayPart(model.items);

    return (
        <>
            <TextField {...field(model.description)} />
            {items?.map((item, index) => (
                <InvoiceItemForm key={index} model={item} remove={() => setValue(value!.filter((_, i) => i !== index))}/>
            ))}
            <Button onClick={() => setValue([...(value ?? []), InvoiceItemModel.createEmptyValue()])}>Add item</Button>
        </>
    );
}

The java entity looks like this

@Entity
@Table(name = "transactions")
...
public class Transaction {

...

  @OneToMany(mappedBy = "transaction", cascade = CascadeType.ALL)
  private List<InvoiceItem> items = new ArrayList<>();

}

@Entity
@Table(name = "invoice_items")
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Getter
@Setter
public class InvoiceItem {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long itemId;

  @ManyToOne
  @JoinColumn(name = "transaction_id", nullable = false)
  private Transaction transaction;

  @NotNull
  @Min(1)
  private Integer quantity;

}

System Info

I use Vaadin version 24.6.0. Java 23, Lombok.

[KardonskyRoman]

👍 I have been using workaround for this behavier more than 2 years in different projects and thought this is done on purpose. Great to see it will be fixed