Do not ever set title to null (#13430)

* If title is null, leave it as-is (assume somebody else is setting it)
* If title is non-null, set it as before

Change-Id: I72699efa089df64b58448ceef59ba31995f330bf

client/src/com/vaadin/client/ui/ui/UIConnector.java

@@ -680,8 +680,10 @@ public class UIConnector extends AbstractSingleComponentContainerConnector
         }
 
         if (stateChangeEvent.hasPropertyChanged("pageState.title")) {
-            com.google.gwt.user.client.Window
-                    .setTitle(getState().pageState.title);
+            String title = getState().pageState.title;
+            if (title != null) {
+                com.google.gwt.user.client.Window.setTitle(title);
+            }
         }
 
         if (stateChangeEvent.hasPropertyChanged("pushConfiguration")) {

server/src/com/vaadin/server/Page.java

@@ -1133,9 +1133,12 @@ public class Page implements Serializable {
     /**
      * Sets the page title. The page title is displayed by the browser e.g. as
      * the title of the browser window or as the title of the tab.
+     * <p>
+     * If the title is set to null, it will not left as-is. Set to empty string
+     * to clear the title.
      * 
      * @param title
-     *            the new page title to set
+     *            the page title to set
      */
     public void setTitle(String title) {
         getState(true).title = title;

shared/src/com/vaadin/shared/ui/ui/PageState.java

@@ -32,7 +32,7 @@ public class PageState implements Serializable {
     public boolean hasResizeListeners = false;
 
     /**
-     * Non-null if the title is set.
+     * Non-null if the title is set. Null means Vaadin does not touch the title.
      */
     public String title = null;
 }

uitest/src/com/vaadin/tests/components/page/PageTitle.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2000-2013 Vaadin Ltd.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.tests.components.page;
+
+import com.vaadin.annotations.Title;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUI;
+
+@Title("bar")
+public class PageTitle extends AbstractTestUI {
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        String title = request.getParameter("title");
+        if (title != null) {
+            getPage().setTitle(title);
+        }
+
+    }
+
+    @Override
+    protected String getTestDescription() {
+        return "Sets the title according to a given ?title parameter. By default the ApplicationServletRunner will set the title to the fully qualified class name";
+    }
+
+    @Override
+    protected Integer getTicketNumber() {
+        return 13430;
+    }
+
+}

uitest/src/com/vaadin/tests/components/page/PageTitleTest.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2000-2013 Vaadin Ltd.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.tests.components.page;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.vaadin.tests.tb3.MultiBrowserTest;
+
+public class PageTitleTest extends MultiBrowserTest {
+
+    @Test
+    public void nullTitle() {
+        driver.get(getTestUrl());
+        Assert.assertEquals(PageTitle.class.getName(), driver.getTitle());
+    }
+
+    @Test
+    public void fooTitle() {
+        driver.get(getTestUrl() + "?title=foo");
+        Assert.assertEquals("foo", driver.getTitle());
+    }
+}