DatePicker looses value with readBean(null) is invoked even if it is set later

[erikcsik]

Description of the bug

Hi,

We have a datepicker binded, if within the same request flow the binder readbean is invoked two times: readBean(null); readBean(myBean); The datepicker looeses value even if the myBean.getDateField() returns a valid localdate.

Expected behavior

If the second readBean object contains valid value for the binded field it should be filled for the DatePicker.

Minimal reproducible example

    private TextField textField = new TextField();
    private Button button = new Button("Test");
    DatePicker datePick = new DatePicker();
    Binder<MyBean> binder = new Binder<MyBean>(MyBean.class);

    public HelloWorldView() {
        add(textField, datePick, button);
        binder.forField(textField).bind("name");
        binder.forField(datePick).bind("localDate");
        MyBean myBean = new MyBean();
        myBean.setLocalDate(LocalDate.now());
        myBean.setName("Test");
        binder.readBean(myBean);
        button.addClickListener(e -> {
            MyBean myBean2 = new MyBean();
            try {
                binder.writeBean(myBean2);
            } catch (ValidationException ex) {
                throw new RuntimeException(ex);
            }
            binder.readBean(null);
            binder.readBean(myBean2);
        });
    }

    public static class MyBean {
        private LocalDate localDate;
        private String name;

        public LocalDate getLocalDate() {
            return localDate;
        }

        public void setLocalDate(LocalDate localDate) {
            this.localDate = localDate;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }
    }

Versions

• Vaadin / Flow version: 24.6.7
• Java version: 21

[TatuLund]

The workaround is to postpone the second read after next client round trip using e.g.

        button.addClickListener(e -> {
            MyBean myBean2 = new MyBean();
            try {
                binder.writeBean(myBean2);
            } catch (ValidationException ex) {
                throw new RuntimeException(ex);
            }
            binder.readBean(null);
            getElement().executeJs("setTimeout(function() { }, 0)").then(result -> binder.readBean(myBean2));
        });

[vursen]

Seems to be the same issue as https://github.com/vaadin/flow-components/issues/7250