Introduce empty selection functionality for NativeSelect. (#8336)

* Introduce empty selection functionality for NativeSelect.

Fixes vaadin/framework8-issues#545

3 files changed, 82 insertions, 2 deletions

diff --git a/server/src/main/java/com/vaadin/ui/NativeSelect.java b/server/src/main/java/com/vaadin/ui/NativeSelect.java
index 9ae3409b66..f7427568ff 100644
--- a/server/src/main/java/com/vaadin/ui/NativeSelect.java
+++ b/server/src/main/java/com/vaadin/ui/NativeSelect.java
@@ -17,6 +17,7 @@
 package com.vaadin.ui;
 
 import java.util.Collection;
+import java.util.Objects;
 
 import com.vaadin.data.HasDataProvider;
 import com.vaadin.data.provider.DataProvider;
@@ -139,4 +140,59 @@ public class NativeSelect<T> extends AbstractSingleSelect<T>
     public ItemCaptionGenerator<T> getItemCaptionGenerator() {
         return super.getItemCaptionGenerator();
     }
+
+    /**
+     * Returns whether the user is allowed to select nothing in the combo box.
+     *
+     * @return true if empty selection is allowed, false otherwise
+     */
+    public boolean isEmptySelectionAllowed() {
+        return getState(false).emptySelectionAllowed;
+    }
+
+    /**
+     * Sets whether the user is allowed to select nothing in the combo box. When
+     * true, a special empty item is shown to the user.
+     *
+     * @param emptySelectionAllowed
+     *            true to allow not selecting anything, false to require
+     *            selection
+     */
+    public void setEmptySelectionAllowed(boolean emptySelectionAllowed) {
+        getState().emptySelectionAllowed = emptySelectionAllowed;
+    }
+
+    /**
+     * Returns the empty selection caption.
+     * <p>
+     * The empty string {@code ""} is the default empty selection caption.
+     *
+     * @see #setEmptySelectionAllowed(boolean)
+     * @see #isEmptySelectionAllowed()
+     * @see #setEmptySelectionCaption(String)
+     * @see #isSelected(Object)
+     *
+     * @return the empty selection caption, not {@code null}
+     */
+    public String getEmptySelectionCaption() {
+        return getState(false).emptySelectionCaption;
+    }
+
+    /**
+     * Sets the empty selection caption.
+     * <p>
+     * The empty string {@code ""} is the default empty selection caption.
+     * <p>
+     * If empty selection is allowed via the
+     * {@link #setEmptySelectionAllowed(boolean)} method (it is by default) then
+     * the empty item will be shown with the given caption.
+     *
+     * @param caption
+     *            the caption to set, not {@code null}
+     * @see #isSelected(Object)
+     */
+    public void setEmptySelectionCaption(String caption) {
+        Objects.nonNull(caption);
+        getState().emptySelectionCaption = caption;
+    }
 }
diff --git a/server/src/test/java/com/vaadin/tests/server/component/combobox/ComboBoxDeclarativeTest.java b/server/src/test/java/com/vaadin/tests/server/component/combobox/ComboBoxDeclarativeTest.java
index 1677f8699b..e2a0c67f2a 100644
--- a/server/src/test/java/com/vaadin/tests/server/component/combobox/ComboBoxDeclarativeTest.java
+++ b/server/src/test/java/com/vaadin/tests/server/component/combobox/ComboBoxDeclarativeTest.java
@@ -48,12 +48,14 @@ public class ComboBoxDeclarativeTest
         int pageLength = 7;
         String popupWidth = "11%";
         boolean emptySelectionAllowed = false;
+        String emptySelectionCaption = "foo";
 
         String design = String.format(
                 "<%s placeholder='%s' text-input-allowed='%s' page-length='%d' "
-                        + "popup-width='%s' empty-selection-allowed='%s' scroll-to-selected-item/>",
+                        + "popup-width='%s' empty-selection-allowed='%s' "
+                        + "scroll-to-selected-item empty-selection-caption='%s'/>",
                 getComponentTag(), placeholder, textInputAllowed, pageLength,
-                popupWidth, emptySelectionAllowed);
+                popupWidth, emptySelectionAllowed, emptySelectionCaption);
 
         ComboBox<String> comboBox = new ComboBox<>();
         comboBox.setPlaceholder(placeholder);
@@ -62,6 +64,7 @@ public class ComboBoxDeclarativeTest
         comboBox.setPopupWidth(popupWidth);
         comboBox.setScrollToSelectedItem(true);
         comboBox.setEmptySelectionAllowed(emptySelectionAllowed);
+        comboBox.setEmptySelectionCaption(emptySelectionCaption);
 
         testRead(design, comboBox);
         testWrite(design, comboBox);
diff --git a/server/src/test/java/com/vaadin/tests/server/component/nativeselect/NativeSelectDeclarativeTest.java b/server/src/test/java/com/vaadin/tests/server/component/nativeselect/NativeSelectDeclarativeTest.java
index 2b80546e80..fea6ac3b12 100644
--- a/server/src/test/java/com/vaadin/tests/server/component/nativeselect/NativeSelectDeclarativeTest.java
+++ b/server/src/test/java/com/vaadin/tests/server/component/nativeselect/NativeSelectDeclarativeTest.java
@@ -15,6 +15,8 @@
  */
 package com.vaadin.tests.server.component.nativeselect;
 
+import org.junit.Test;
+
 import com.vaadin.tests.server.component.abstractsingleselect.AbstractSingleSelectDeclarativeTest;
 import com.vaadin.ui.NativeSelect;
 
@@ -29,6 +31,25 @@ import com.vaadin.ui.NativeSelect;
 public class NativeSelectDeclarativeTest
         extends AbstractSingleSelectDeclarativeTest<NativeSelect> {
 
+    @Test
+    public void nativeSelectSpecificPropertiesSerialize() {
+        boolean emptySelectionAllowed = false;
+        String emptySelectionCaption = "foo";
+
+        String design = String.format(
+                "<%s empty-selection-allowed='%s' "
+                        + "empty-selection-caption='%s'/>",
+                getComponentTag(), emptySelectionAllowed,
+                emptySelectionCaption);
+
+        NativeSelect<String> select = new NativeSelect<>();
+        select.setEmptySelectionAllowed(emptySelectionAllowed);
+        select.setEmptySelectionCaption(emptySelectionCaption);
+
+        testRead(design, select);
+        testWrite(design, select);
+    }
+
     @Override
     protected String getComponentTag() {
         return "vaadin-native-select";