Fix VComboBox internal state cleanup (#10693)

Fixes vaadin/testbench#1009

client/src/main/java/com/vaadin/client/ui/VComboBox.java

             return $entry(function(e) {
                 var deltaX = e.deltaX ? e.deltaX : -0.5*e.wheelDeltaX;
                 var deltaY = e.deltaY ? e.deltaY : -0.5*e.wheelDeltaY;
-
+        
                 // IE8 has only delta y
                 if (isNaN(deltaY)) {
                     deltaY = -0.5*e.wheelDelta;
                 }
-
+        
                 @com.vaadin.client.ui.VComboBox.JsniUtil::moveScrollFromEvent(*)(widget, deltaX, deltaY, e, e.deltaMode);
             });
         }-*/;
          */
         private void cancelPendingPostFiltering() {
             pendingUserInput = null;
+            waitingForFilteringResponse = false;
         }
 
         /**

client/src/main/java/com/vaadin/client/ui/combobox/ComboBoxConnector.java

             getWidget().selectedOptionKey = null;
             getWidget().currentSuggestion = null;
         }
+        if (isNewItemStillPending()
+                && pendingNewItemValue == getState().selectedItemCaption) {
+            // no automated selection handling required
+            clearNewItemHandling();
+        }
         getDataReceivedHandler().updateSelectionFromServer(
                 getState().selectedItemKey, getState().selectedItemCaption,
                 getState().selectedItemIcon);

uitest/src/main/java/com/vaadin/tests/components/combobox/ComboBoxTestBenchPerformance.java

+package com.vaadin.tests.components.combobox;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.vaadin.annotations.Widgetset;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.ComboBox;
+
+@Widgetset("com.vaadin.DefaultWidgetSet")
+public class ComboBoxTestBenchPerformance extends AbstractTestUI {
+
+    @SuppressWarnings("deprecation")
+    @Override
+    protected void setup(VaadinRequest request) {
+        List<String> items = new ArrayList<>();
+        for (int i = 0; i < 20; i++) {
+            items.add(i + "");
+        }
+        ComboBox<String> combo = new ComboBox<>("ComboBox with NewItemHandler");
+        combo.setItems(items);
+        combo.setEmptySelectionAllowed(false);
+        combo.setNewItemHandler(inputString -> {
+            items.add(inputString);
+            combo.setItems(items);
+            combo.setSelectedItem(inputString);
+        });
+        combo.setSelectedItem(items.iterator().next());
+        addComponent(combo);
+    }
+
+    @Override
+    protected String getTestDescription() {
+        return "Selecting values through TestBench shouldn't take minutes.";
+    }
+
+    @Override
+    protected Integer getTicketNumber() {
+        return 10284;
+    }
+}

uitest/src/test/java/com/vaadin/tests/components/combobox/ComboBoxSelectingWithNewItemsAllowedTest.java

     }
 
     @Test
-    public void noSelectionAfterMouseOut() {
+    public void selectionOnMouseOut() {
         typeInputAndHitEnter("a20");
         comboBoxElement.sendKeys(Keys.ARROW_DOWN, Keys.ARROW_DOWN);
 
         findElement(By.className("v-app")).click();
 
         assertInitialItemCount();
-        assertThatSelectedValueIs("a20");
+        assertThatSelectedValueIs("", "null");
     }
 
     @Test

uitest/src/test/java/com/vaadin/tests/components/combobox/ComboBoxTestBenchPerformanceTest.java

+package com.vaadin.tests.components.combobox;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.number.IsCloseTo.closeTo;
+
+import org.junit.Test;
+import org.openqa.selenium.Keys;
+
+import com.vaadin.testbench.elements.ComboBoxElement;
+import com.vaadin.tests.tb3.SingleBrowserTest;
+
+public class ComboBoxTestBenchPerformanceTest extends SingleBrowserTest {
+
+    /**
+     * TestBench timeout is 20s, require 15s to make sure cluster load won't
+     * affect the result badly.
+     */
+    private static final double TIME_LIMIT = 15000d;
+
+    @Test
+    public void testSelectionPerformance() throws Exception {
+        openTestURL();
+
+        long before = System.currentTimeMillis();
+        setComboBoxValue("abc123"); // new
+        long after = System.currentTimeMillis();
+        assertThat((double) after - before, closeTo(0d, TIME_LIMIT));
+
+        before = System.currentTimeMillis();
+        setComboBoxValue("11"); // existing (2nd page)
+        after = System.currentTimeMillis();
+        assertThat((double) after - before, closeTo(0d, TIME_LIMIT));
+
+        before = System.currentTimeMillis();
+        setComboBoxValue("abc123"); // previously added (3rd page)
+        after = System.currentTimeMillis();
+        assertThat((double) after - before, closeTo(0d, TIME_LIMIT));
+    }
+
+    public void setComboBoxValue(final String value) {
+        ComboBoxElement combobox = $(ComboBoxElement.class).first();
+        if (combobox.getPopupSuggestions().contains(value)) {
+            // Select existing item
+            combobox.selectByText(value);
+        } else {
+            // Enter new item
+            combobox.clear();
+            combobox.sendKeys(value);
+            combobox.sendKeys(Keys.ENTER);
+        }
+
+        // Make sure Vaadin is ready before leaving the method
+        testBench().waitForVaadin();
+    }
+}