Add missing Grid.removeAllColumns (#8750)

Fixes #8704

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

@@ -2323,6 +2323,15 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
         removeColumn(getColumnOrThrow(columnId));
     }
 
+    /**
+     * Removes all columns from this Grid.
+     */
+    public void removeAllColumns() {
+        for (Column<T, ?> column : getColumns()) {
+            removeColumn(column);
+        }
+    }
+
     /**
      * Sets the details component generator.
      *

server/src/test/java/com/vaadin/tests/server/component/grid/GridTest.java

@@ -403,6 +403,20 @@ public class GridTest {
                 grid.getColumns());
     }
 
+    @Test
+    public void removeAllColumns() {
+        grid.removeAllColumns();
+
+        Assert.assertEquals(Collections.emptyList(), grid.getColumns());
+    }
+
+    @Test
+    public void removeAllColumnsInGridWithoutColumns() {
+        grid.removeAllColumns();
+        grid.removeAllColumns();
+        Assert.assertEquals(Collections.emptyList(), grid.getColumns());
+    }
+
     @Test
     public void setColumns_reorder() {
         // Will remove other columns