Adding stylename to MenuBarItem also as one word (#10704)

Fixes #7912

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

@@ -967,6 +967,7 @@ FocusHandler, SubPartAware, MouseOutHandler, MouseOverHandler {
 
             if (styleName != null) {
                 addStyleDependentName(styleName);
+                addStyleName(styleName);
             }
 
             if (enabled) {

uitest/src/main/java/com/vaadin/tests/components/menubar/MenuItemStyleAdd.java

@@ -0,0 +1,31 @@
+package com.vaadin.tests.components.menubar;
+
+import com.vaadin.annotations.Widgetset;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.MenuBar;
+
+@Widgetset("com.vaadin.DefaultWidgetSet")
+public class MenuItemStyleAdd extends AbstractTestUI {
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        MenuBar barmenu = new MenuBar();
+        MenuBar.MenuItem more = barmenu.addItem("More", null, null);
+        more.setStyleName("styleNameMore");
+        barmenu.setMoreMenuItem(more);
+
+        MenuBar.MenuItem drinks = barmenu.addItem("Drinks", null, null);
+        MenuBar.MenuItem hots = drinks.addItem("Hot", null, null);
+        hots.addItem("Tea", null);
+        hots.addItem("Coffee", null);
+        hots.setStyleName("styleTest");
+
+        MenuBar.MenuItem colds = drinks.addItem("Cold", null, null);
+        colds.addItem("Milk", null);
+        colds.addItem("Weissbier", null);
+
+        addComponent(barmenu);
+    }
+
+}

uitest/src/test/java/com/vaadin/tests/components/menubar/MenuItemStyleAddTest.java

@@ -0,0 +1,38 @@
+package com.vaadin.tests.components.menubar;
+
+import com.vaadin.testbench.By;
+import com.vaadin.testbench.elements.MenuBarElement;
+import com.vaadin.tests.tb3.MultiBrowserTest;
+import org.junit.Test;
+import org.openqa.selenium.WebElement;
+import static org.junit.Assert.assertEquals;
+
+import java.util.List;
+
+public class MenuItemStyleAddTest extends MultiBrowserTest {
+
+    @Test
+    public void testCustomStyleShouldStayAfterMenuSelect() {
+        openTestURL();
+
+        MenuBarElement menu = $(MenuBarElement.class).first();
+        List<WebElement> elements = menu
+                .findElements(By.className("v-menubar-menuitem"));
+        WebElement more = elements.get(0);
+        assertEquals(true,
+                more.getAttribute("class")
+                        .replaceAll("v-menubar-menuitem-styleNameMore", "")
+                        .contains("styleNameMore"));
+        assertEquals(2, elements.size());
+        menu.clickItem("Drinks");
+        WebElement popup = getDriver()
+                .findElement(By.className("v-menubar-popup"));
+        List<WebElement> popupElCon = popup
+                .findElements(By.className("styleTest"));
+        assertEquals(1, popupElCon.size());
+        assertEquals(true,
+                popupElCon.get(0).getAttribute("class")
+                        .replaceAll("v-menubar-menuitem-styleTest", "")
+                        .contains("styleTest"));
+    }
+}