Fix null selection to work again (#19787)

Reverts the fix for #15181

Change-Id: I9ec45b1c9aad9788559d0de2b086bf5cf4af6b12

4 files changed, 69 insertions, 7 deletions

diff --git a/server/src/main/java/com/vaadin/server/KeyMapper.java b/server/src/main/java/com/vaadin/server/KeyMapper.java
index 0e4b7edc77..709c3e0c2d 100644
--- a/server/src/main/java/com/vaadin/server/KeyMapper.java
+++ b/server/src/main/java/com/vaadin/server/KeyMapper.java
@@ -93,4 +93,18 @@ public class KeyMapper<V> implements Serializable {
         objectKeyMap.clear();
         keyObjectMap.clear();
     }
+
+    /**
+     * Checks if the given key is mapped to an object.
+     * 
+     * @since
+     * 
+     * @param key
+     *            the key to check
+     * @return <code>true</code> if the key is currently mapped,
+     *         <code>false</code> otherwise
+     */
+    public boolean containsKey(String key) {
+        return keyObjectMap.containsKey(key);
+    }
 }
diff --git a/server/src/main/java/com/vaadin/ui/AbstractSelect.java b/server/src/main/java/com/vaadin/ui/AbstractSelect.java
index 2714e0cbf5..882458c531 100644
--- a/server/src/main/java/com/vaadin/ui/AbstractSelect.java
+++ b/server/src/main/java/com/vaadin/ui/AbstractSelect.java
@@ -530,18 +530,21 @@ public abstract class AbstractSelect extends AbstractField<Object> implements
                         setValue(null, true);
                     }
                 } else {
-                    final Object id = itemIdMapper
-                            .get(clientSideSelectedKeys[0]);
-
-                    if (id != null) {
-                        if (isNullSelectionAllowed()
+                    String clientSelectedKey = clientSideSelectedKeys[0];
+                    if ("null".equals(clientSelectedKey)
+                            || itemIdMapper.containsKey(clientSelectedKey)) {
+                        // Happens to work for nullselection
+                        // (get ("null") -> null))
+                        final Object id = itemIdMapper.get(clientSelectedKey);
+
+                        if (!isNullSelectionAllowed() && id == null) {
+                            markAsDirty();
+                        } else if (id != null
                                 && id.equals(getNullSelectionItemId())) {
                             setValue(null, true);
                         } else {
                             setValue(id, true);
                         }
-                    } else {
-                        markAsDirty();
                     }
                 }
             }
diff --git a/uitest/src/main/java/com/vaadin/tests/components/nativeselect/NativeSelectNull.java b/uitest/src/main/java/com/vaadin/tests/components/nativeselect/NativeSelectNull.java
new file mode 100644
index 0000000000..fb5914f395
--- /dev/null
+++ b/uitest/src/main/java/com/vaadin/tests/components/nativeselect/NativeSelectNull.java
@@ -0,0 +1,25 @@
+package com.vaadin.tests.components.nativeselect;
+
+import com.vaadin.data.Property.ValueChangeEvent;
+import com.vaadin.data.Property.ValueChangeListener;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUIWithLog;
+import com.vaadin.ui.NativeSelect;
+
+public class NativeSelectNull extends AbstractTestUIWithLog {
+    @Override
+    protected void setup(VaadinRequest request) {
+        NativeSelect nativeSelect = new NativeSelect();
+        nativeSelect.addItem("Item");
+        nativeSelect.addValueChangeListener(new ValueChangeListener() {
+
+            @Override
+            public void valueChange(ValueChangeEvent event) {
+                log("Value: " + event.getProperty().getValue());
+
+            }
+        });
+        addComponent(nativeSelect);
+    }
+
+}
diff --git a/uitest/src/test/java/com/vaadin/tests/components/nativeselect/NativeSelectNullTest.java b/uitest/src/test/java/com/vaadin/tests/components/nativeselect/NativeSelectNullTest.java
new file mode 100644
index 0000000000..613efbb566
--- /dev/null
+++ b/uitest/src/test/java/com/vaadin/tests/components/nativeselect/NativeSelectNullTest.java
@@ -0,0 +1,20 @@
+package com.vaadin.tests.components.nativeselect;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.vaadin.testbench.elements.NativeSelectElement;
+import com.vaadin.tests.tb3.SingleBrowserTest;
+import com.vaadin.tests.tb3.SingleBrowserTestPhantomJS2;
+
+public class NativeSelectNullTest extends SingleBrowserTestPhantomJS2 {
+    @Test
+    public void selectNull() {
+        openTestURL();
+        NativeSelectElement select = $(NativeSelectElement.class).first();
+        select.selectByText("Item");
+        Assert.assertEquals("1. Value: Item", getLogRow(0));
+        select.selectByText("");
+        Assert.assertEquals("2. Value: null", getLogRow(0));
+    }
+}