fix: Ensure row is visible before getting it

vaadin-grid-flow-parent/vaadin-grid-flow-integration-tests/src/test/java/com/vaadin/flow/component/grid/it/ComponentColumnWithHeightIT.java

@@ -54,15 +54,14 @@ public void shouldPositionItemsCorrectlyAfterUpdatingComponentRenderers() {
 
     @Test
     public void shouldPositionItemsCorrectlyAfterScrollingToEnd() {
-        int initialLastRow = grid.getRowCount() - 1;
-        grid.scrollToRow(initialLastRow);
+        var initialLastRow = grid.getRowCount() - 1;
+        var row = grid.getRow(initialLastRow, true);
+        var expectedPosition = row.getLocation().y + row.getSize().height;
 
         add.click();
         // Expect the y position of the last row to equal the y position + the
         // height of the previous row
-        Assert.assertEquals(
-                grid.getRow(initialLastRow).getLocation().y
-                        + grid.getRow(initialLastRow).getSize().height,
+        Assert.assertEquals(expectedPosition,
                 grid.getRow(initialLastRow + 1).getLocation().y);
     }
 }

vaadin-grid-flow-parent/vaadin-grid-testbench/src/main/java/com/vaadin/flow/component/grid/testbench/GridElement.java

@@ -234,15 +234,40 @@ public List<GridTRElement> getRows(int firstRowIndex, int lastRowIndex)
     }
 
     /**
-     * Gets the <code>tr</code> element for the given row index.
+     * Gets the {@code tr} element for the given row index.
      *
      * @param rowIndex
      *            the row index
-     * @return the tr element for the row
+     * @return the {@code tr} element for the row, or {@code null} if the row is
+     *         not in viewport
      * @throws IndexOutOfBoundsException
      *             if no row with given index exists
      */
     public GridTRElement getRow(int rowIndex) throws IndexOutOfBoundsException {
+        return getRow(rowIndex, false);
+    }
+
+    /**
+     * Gets the {@code tr} element for the given row index.
+     * <p>
+     * Returns {@code null} if the row is not in viewport and the provided
+     * {@code scroll} parameter is {@code false}.
+     *
+     * @param rowIndex
+     *            the row index
+     * @param scroll
+     *            whether to scroll to the row index
+     * @return the {@code tr} element for the row, or {@code null} if the row is
+     *         not in viewport and the provided {@code scroll} parameter is
+     *         {@code false}
+     * @throws IndexOutOfBoundsException
+     *             if no row with given index exists
+     */
+    public GridTRElement getRow(int rowIndex, boolean scroll)
+            throws IndexOutOfBoundsException {
+        if (scroll && !isRowInView(rowIndex)) {
+            scrollToFlatRow(rowIndex);
+        }
         var rows = getRows(rowIndex, rowIndex);
         return rows.size() == 1 ? rows.get(0) : null;
     }