Don't remove frozen columns when columns reordered in Grid #16901

Change-Id: Ib812ecd6afeb92d56bb179bcb120c65f20d26a8c

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

@@ -4680,7 +4680,6 @@ public class Grid<T> extends ResizeComposite implements
 
         escalator.getColumnConfiguration()
                 .setFrozenColumnCount(numberOfColumns);
-
     }
 
     /**
@@ -5960,6 +5959,9 @@ public class Grid<T> extends ResizeComposite implements
         // Do ComplexRenderer.init and render new content
         conf.insertColumns(0, columns.size());
 
+        // Number of frozen columns should be kept same #16901
+        updateFrozenColumns();
+
         // Update column widths.
         for (Column<?, T> column : columns) {
             column.reapplyWidth();

uitest/src/com/vaadin/tests/components/grid/basicfeatures/client/GridClientColumnPropertiesTest.java

@@ -93,6 +93,23 @@ public class GridClientColumnPropertiesTest extends GridBasicClientFeaturesTest
         assertFalse(cellIsFrozen(1, 0));
     }
 
+    @Test
+    public void testFrozenColumns_columnsReordered_frozenColumnsKept() {
+        openTestURL();
+
+        selectMenuPath("Component", "State", "Frozen column count", "2 columns");
+
+        assertTrue(cellIsFrozen(1, 0));
+        assertTrue(cellIsFrozen(1, 1));
+        assertFalse(cellIsFrozen(1, 2));
+
+        selectMenuPath("Component", "State", "Reverse grid columns");
+
+        assertTrue(cellIsFrozen(1, 0));
+        assertTrue(cellIsFrozen(1, 1));
+        assertFalse(cellIsFrozen(1, 2));
+    }
+
     @Test
     public void testBrokenRenderer() {
         setDebug(true);