Display the caption of the Empty selection in NativeSelect (#11191)

* Fixes #10937

- Previously if selected value is null, then index is set to -1; in current implementation if value is null and emptySelection is allowed then set the index to 0. (The position for the empty selection)

- Also, if changing the allowEmptySelection on the fly, ensure, that either index is to-reset to -1 by setting the selected value to null on the client-side (the value before was null) or preserve the value(value was different than empty).

* Change the test case

Since in this pr the behaviour of the NS is changed, therefore old test need to be adjusted.

Change: setting null as value will select empty selection. Before that nothing would be selected and value will be cleared.

Behaviour change in PR: Allow selecting null as value

2 files changed, 29 insertions, 1 deletions

diff --git a/client/src/main/java/com/vaadin/client/ui/VNativeSelect.java b/client/src/main/java/com/vaadin/client/ui/VNativeSelect.java
index f6980050b6..f92aa05e42 100644
--- a/client/src/main/java/com/vaadin/client/ui/VNativeSelect.java
+++ b/client/src/main/java/com/vaadin/client/ui/VNativeSelect.java
@@ -29,6 +29,7 @@ import com.vaadin.shared.ui.nativeselect.NativeSelectState;
 public class VNativeSelect extends FocusableFlowPanelComposite {
 
     private final ListBox listBox = new ListBox();
+    private boolean emptySelectionAllowed = true;
 
     /**
      * Creates a new {@code VNativeSelect} instance.
@@ -55,7 +56,11 @@ public class VNativeSelect extends FocusableFlowPanelComposite {
      */
     public void setSelectedItem(String value) {
         if (value == null) {
-            getListBox().setSelectedIndex(-1);
+            if (emptySelectionAllowed) {
+                getListBox().setSelectedIndex(0);
+            } else {
+                getListBox().setSelectedIndex(-1);
+            }
         } else {
             for (int i = 0; i < getListBox().getItemCount(); i++) {
                 if (Objects.equals(value, getListBox().getValue(i))) {
@@ -132,4 +137,23 @@ public class VNativeSelect extends FocusableFlowPanelComposite {
         return getListBox().getVisibleItemCount();
     }
 
+    /**
+     * Returns true if empty selection is allowed.
+     *
+     * @since
+     * @return empty selection is allowed
+     */
+    public boolean isEmptySelectionAllowed() {
+        return emptySelectionAllowed;
+    }
+
+    /**
+     * Sets true if empty selection is allowed.
+     *
+     * @since
+     * @param emptySelectionAllowed
+     */
+    public void setEmptySelectionAllowed(boolean emptySelectionAllowed) {
+        this.emptySelectionAllowed = emptySelectionAllowed;
+    }
 }
diff --git a/client/src/main/java/com/vaadin/client/ui/nativeselect/NativeSelectConnector.java b/client/src/main/java/com/vaadin/client/ui/nativeselect/NativeSelectConnector.java
index 44b6c3b831..5f17ac4e64 100644
--- a/client/src/main/java/com/vaadin/client/ui/nativeselect/NativeSelectConnector.java
+++ b/client/src/main/java/com/vaadin/client/ui/nativeselect/NativeSelectConnector.java
@@ -95,10 +95,14 @@ public class NativeSelectConnector
         ListBox listBox = getWidget().getListBox();
         boolean hasEmptyItem = listBox.getItemCount() > 0
                 && listBox.getValue(0).isEmpty();
+        getWidget().setEmptySelectionAllowed(getState().emptySelectionAllowed);
         if (hasEmptyItem && getState().emptySelectionAllowed) {
             listBox.setItemText(0, getState().emptySelectionCaption);
         } else if (hasEmptyItem && !getState().emptySelectionAllowed) {
             listBox.removeItem(0);
+            if (getWidget().getListBox().getSelectedIndex() == 0) {
+                getWidget().setSelectedItem(null);
+            }
         } else if (!hasEmptyItem && getState().emptySelectionAllowed) {
             listBox.insertItem(getState().emptySelectionCaption, 0);
             listBox.setValue(0, "");