2 files changed, 5 insertions, 24 deletions
diff --git a/server/src/main/java/com/vaadin/ui/AbstractSingleSelect.java b/server/src/main/java/com/vaadin/ui/AbstractSingleSelect.java
index 2b0e6b7d01..f9eed7fef3 100644
--- a/server/src/main/java/com/vaadin/ui/AbstractSingleSelect.java
+++ b/server/src/main/java/com/vaadin/ui/AbstractSingleSelect.java
@@ -230,10 +230,8 @@ public abstract class AbstractSingleSelect<T> extends AbstractListing<T>
         T oldSelection = getSelectedItem().orElse(getEmptyValue());
         doSetSelectedKey(key);
 
-        // Update diffstate so that a change will be sent to the client if the
-        // selection is changed to its original value
-        updateDiffstate("selectedItemKey",
-                key == null ? Json.createNull() : Json.create(key));
+        // Set diffstate to something that will always send selection to client
+        updateDiffstate("selectedItemKey", Json.createObject());
 
         fireEvent(new SingleSelectionEvent<>(AbstractSingleSelect.this,
                 oldSelection, true));
diff --git a/server/src/main/java/com/vaadin/ui/ComboBox.java b/server/src/main/java/com/vaadin/ui/ComboBox.java
index 73d9ad84cf..af100e03f1 100644
--- a/server/src/main/java/com/vaadin/ui/ComboBox.java
+++ b/server/src/main/java/com/vaadin/ui/ComboBox.java
@@ -25,11 +25,11 @@ import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Stream;
 
-import com.vaadin.data.ValueProvider;
 import org.jsoup.nodes.Element;
 
 import com.vaadin.data.HasFilterableDataProvider;
 import com.vaadin.data.HasValue;
+import com.vaadin.data.ValueProvider;
 import com.vaadin.data.provider.CallbackDataProvider;
 import com.vaadin.data.provider.DataCommunicator;
 import com.vaadin.data.provider.DataKeyMapper;
@@ -57,7 +57,6 @@ import com.vaadin.ui.declarative.DesignAttributeHandler;
 import com.vaadin.ui.declarative.DesignContext;
 import com.vaadin.ui.declarative.DesignFormatter;
 
-import elemental.json.Json;
 import elemental.json.JsonObject;
 
 /**
@@ -189,7 +188,8 @@ public class ComboBox<T> extends AbstractSingleSelect<T>
     public ComboBox() {
         super(new DataCommunicator<T>() {
             @Override
-            protected DataKeyMapper<T> createKeyMapper(ValueProvider<T,Object> identifierGetter) {
+            protected DataKeyMapper<T> createKeyMapper(
+                    ValueProvider<T, Object> identifierGetter) {
                 return new KeyMapper<T>(identifierGetter) {
                     @Override
                     public void remove(T removeobj) {
@@ -831,23 +831,6 @@ public class ComboBox<T> extends AbstractSingleSelect<T>
                 q -> sizeCallback.applyAsInt(q.getFilter().orElse(""))));
     }
 
-    @Override
-    protected void setSelectedFromClient(String key) {
-        super.setSelectedFromClient(key);
-
-        /*
-         * The client side for combo box always expects a state change for
-         * selectedItemKey after it has sent a selection change. This means that
-         * we must store a value in the diffstate that guarantees that a new
-         * value will be sent, regardless of what the value actually is at the
-         * time when changes are sent.
-         *
-         * Keys are always strings (or null), so using a non-string type will
-         * always trigger a diff mismatch and a resend.
-         */
-        updateDiffstate("selectedItemKey", Json.create(0));
-    }
-
     /**
      * Predicate to check {@link ComboBox} item captions against user typed
      * strings.