Render null header caption as empty (#18553)

Change-Id: Iaeba81c7e40d4be5f16e74fa8bcf8c86c53a7d3d

client/src/com/vaadin/client/widgets/Grid.java

@@ -4650,12 +4650,10 @@ public class Grid<T> extends ResizeComposite implements
          *            The header caption for this column
          * @return the column itself
          * 
-         * @throws IllegalArgumentException
-         *             if given caption text is null
          */
         public Column<C, T> setHeaderCaption(String caption) {
             if (caption == null) {
-                throw new IllegalArgumentException("Caption cannot be null.");
+                caption = "";
             }
 
             if (!this.headerCaption.equals(caption)) {

server/src/com/vaadin/ui/Grid.java

@@ -3250,7 +3250,9 @@ public class Grid extends AbstractFocusable implements SelectionNotifier,
         public Column setHeaderCaption(String caption)
                 throws IllegalStateException {
             checkColumnIsAttached();
-
+            if (caption == null) {
+                caption = ""; // Render null as empty
+            }
             state.headerCaption = caption;
 
             HeaderRow row = grid.getHeader().getDefaultRow();

uitest/src/com/vaadin/tests/components/grid/NullHeaders.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2000-2014 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.grid;
+
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUIWithLog;
+import com.vaadin.ui.Grid;
+
+public class NullHeaders extends AbstractTestUIWithLog {
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        final Grid grid = new Grid();
+        grid.addColumn("country", String.class);
+        grid.addColumn("foo", String.class);
+        grid.addColumn("bar", Integer.class);
+
+        grid.getColumn("country").setHeaderCaption(null);
+        grid.getColumn("foo").setHeaderCaption("");
+        grid.getColumn("bar").setHeaderCaption(null);
+        grid.addRow("Finland", "foo", 1);
+        grid.addRow("Swaziland", "bar", 2);
+        grid.addRow("Japan", "baz", 3);
+        addComponent(grid);
+    }
+
+}

uitest/src/com/vaadin/tests/components/grid/NullHeadersTest.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2000-2014 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.grid;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.vaadin.testbench.elements.GridElement;
+import com.vaadin.tests.tb3.SingleBrowserTest;
+
+public class NullHeadersTest extends SingleBrowserTest {
+
+    @Test
+    public void gridWithNullHeadersShouldBeRendered() {
+        openTestURL();
+
+        GridElement grid = $(GridElement.class).first();
+
+        Assert.assertEquals(1, grid.getHeaderCount());
+        Assert.assertEquals(3, grid.getHeaderCells(0).size());
+        for (int i = 0; i < 3; i++) {
+            Assert.assertEquals("", grid.getHeaderCell(0, 0).getText());
+        }
+        assertRow(grid, 0, "Finland", "foo", "1");
+        assertRow(grid, 1, "Swaziland", "bar", "2");
+        assertRow(grid, 2, "Japan", "baz", "3");
+    }
+
+    private void assertRow(GridElement grid, int row, String... contents) {
+        for (int col = 0; col < contents.length; col++) {
+            Assert.assertEquals(contents[col], grid.getCell(row, col).getText());
+        }
+
+    }
+}