Fix null selection to work again (#19787)

Reverts the fix for #15181

Change-Id: I9ec45b1c9aad9788559d0de2b086bf5cf4af6b12

2 files changed, 24 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();
                     }
                 }
             }