Fix removing rows from the middle of Escalator (#8826)

* Fix removing rows from the middle of Escalator

Fixes #8825

client/src/main/java/com/vaadin/client/widgets/Escalator.java

@@ -3130,14 +3130,8 @@ public class Escalator extends Widget
                         y += spacerContainer.getSpacerHeight(i);
                     }
 
-                    /*
-                     * this is how many rows appeared into the viewport from
-                     * below
-                     */
-                    final int rowsToUpdateDataOn = numberOfRows
-                            - escalatorRowsToRemove;
-                    final int start = Math.max(0,
-                            escalatorRowCount - rowsToUpdateDataOn);
+                    // #8825 update data starting from the first moved row
+                    final int start = dirtyRowsStart;
                     final int end = escalatorRowCount;
                     for (int i = start; i < end; i++) {
                         final TableRowElement tr = visualRowOrder.get(i);

uitest/src/main/java/com/vaadin/tests/widgetset/client/grid/EscalatorBasicClientFeaturesWidget.java

@@ -540,6 +540,12 @@ public class EscalatorBasicClientFeaturesWidget
                 insertRows(escalator.getBody(), 0, 5);
             }
         }, menupath);
+        addMenuCommand("Add 22 rows to top", new ScheduledCommand() {
+            @Override
+            public void execute() {
+                insertRows(escalator.getBody(), 0, 22);
+            }
+        }, menupath);
         addMenuCommand("Add 50 rows to top", new ScheduledCommand() {
             @Override
             public void execute() {
@@ -560,6 +566,12 @@ public class EscalatorBasicClientFeaturesWidget
                         escalator.getBody().getRowCount() - 50, 50);
             }
         }, menupath);
+        addMenuCommand("Remove 15 rows from middle", new ScheduledCommand() {
+            @Override
+            public void execute() {
+                removeRows(escalator.getBody(), 3, 15);
+            }
+        }, menupath);
         addMenuCommand("Remove 50 rows from almost bottom",
                 new ScheduledCommand() {
                     @Override

uitest/src/test/java/com/vaadin/tests/components/grid/basicfeatures/EscalatorBasicClientFeaturesTest.java

@@ -59,6 +59,8 @@ public abstract class EscalatorBasicClientFeaturesTest
     protected static final String SCROLL_TO = "Scroll to...";
 
     protected static final String REMOVE_ALL_INSERT_SCROLL = "Remove all, insert 30 and scroll 40px";
+    protected static final String ADD_22_ROWS_TO_TOP = "Add 22 rows to top";
+    protected static final String REMOVE_15_ROWS_FROM_MIDDLE = "Remove 15 rows from middle";
 
     protected static final String GENERAL = "General";
     protected static final String DETACH_ESCALATOR = "Detach Escalator";

uitest/src/test/java/com/vaadin/tests/components/grid/basicfeatures/escalator/EscalatorRemoveAndAddRowsTest.java

@@ -19,6 +19,7 @@ import static org.junit.Assert.assertTrue;
 
 import java.io.IOException;
 
+import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 import org.openqa.selenium.By;
@@ -38,7 +39,6 @@ public class EscalatorRemoveAndAddRowsTest
 
     @Test
     public void testRemoveAllRowsAndAddThirtyThenScroll() throws IOException {
-
         selectMenuPath(GENERAL, POPULATE_COLUMN_ROW);
 
         scrollVerticallyTo(99999);
@@ -51,4 +51,33 @@ public class EscalatorRemoveAndAddRowsTest
         assertTrue("Escalator is not scrolled to bottom.",
                 isElementPresent(By.xpath("//td[text() = 'Row 29: 0,129']")));
     }
+
+    @Test
+    public void testRemoveRowsFromMiddle() {
+        selectMenuPath(COLUMNS_AND_ROWS, COLUMNS, ADD_ONE_COLUMN_TO_BEGINNING);
+        selectMenuPath(COLUMNS_AND_ROWS, HEADER_ROWS, ADD_ONE_ROW_TO_BEGINNING);
+        selectMenuPath(COLUMNS_AND_ROWS, BODY_ROWS, ADD_22_ROWS_TO_TOP);
+        // remove enough rows from middle, so that the total size of escalator
+        // rows drops to below the size of the rows shown, forcing the escalator
+        // to remove & move & update rows
+        selectMenuPath(COLUMNS_AND_ROWS, BODY_ROWS, REMOVE_15_ROWS_FROM_MIDDLE);
+        // first there was rows 0-21, then removed 15 rows 3-18, thus the rows
+        // should be 0,1,2,18,19,20,21
+        verifyRow(0, 0);
+        verifyRow(1, 1);
+        verifyRow(2, 2);
+        verifyRow(3, 18);
+        verifyRow(4, 19);
+        verifyRow(5, 20);
+        verifyRow(6, 21);
+    }
+
+    private void verifyRow(int escalatorIndex, int rowIndexInText) {
+        // the format of text in cells is
+        // Row: <index_when_updated>: <cell_index>,<index_when_inserted>
+        Assert.assertEquals("Invalid row present in index " + escalatorIndex,
+                "Row " + escalatorIndex + ": 0," + rowIndexInText,
+                getBodyCell(escalatorIndex, 0).getText());
+    }
+
 }