Happen if we call table.edit(row,... ) on a newly added item off the visible range. Looks like internals get confused.

To reproduce, run the example below

 * - click addAndEdit to insert cell off the visual range and start edit
 * - click scrollBar to scroll to inserted cell
 * - click addAndEdit again
 * - expected: cell with "initial 51" is edited
 * - actual: cell with "initial 50" is edited
 * - type x at beginning of editor text field, commit by enter
 * - note two cells with "xinitial 50"
 * - scroll back and forth to get rid of the visual artefact (only one is really changed)
 * - note that "initial 51" is changed to "xinitial 50" - corrupted data!


The example:

public class TablePCoreAddAndEdit extends Application {

    private Parent getContent() {
        TableView<Dummy> table = new TableView<>(createData(50));
        table.setEditable(true);
        
        TableColumn<Dummy, String> column = new TableColumn<>("Value");
        column.setCellValueFactory(c -> c.getValue().valueProperty());
        column.setCellFactory(TextFieldTableCell.forTableColumn());
        column.setMinWidth(200);
        table.getColumns().addAll(column);
        
        // insert and start editing at an invisible row
        // in my environment, I see about 12 rows
        int insertIndex = 20;
        Button addAndEdit = new Button("AddAndEdit");
        addAndEdit.setOnAction(e -> {
            Dummy dummy = new Dummy();
            table.getItems().add(insertIndex, dummy);
            table.edit(insertIndex, column);
            LOG.info("insertIndex" + insertIndex + "isAtIndex " + table.getItems().indexOf(dummy) + dummy);
        });
        
        Button logEditing = new Button("LogEditing");
        logEditing.setOnAction(e-> {
            TablePosition<?, ?> editingCell = table.getEditingCell();
            LOG.info((editingCell != null
                    ? "editing row: " + editingCell.getRow() + table.getItems().get(editingCell.getRow()): "no editing cell")
                    + "value at insertIndex: " + table.getItems().get(insertIndex)
                    );
        });
        HBox buttons = new HBox(10, addAndEdit, logEditing);
        BorderPane content = new BorderPane(table);
        content.setBottom(buttons);
        return content;
    }

    private ObservableList<Dummy> createData(int size) {
        return FXCollections.observableArrayList(
                Stream.generate(Dummy::new)
                .limit(size)
                .collect(Collectors.toList()));
    }
    
    private static class Dummy {
        private static int count;
        StringProperty value = new SimpleStringProperty(this, "value", "initial " + count++);
        public StringProperty valueProperty() {return value;}
        public String getValue() {return valueProperty().get(); }
        public void setValue(String text) {valueProperty().set(text); }
        public String toString() {return "[dummy: " + getValue() + "]";}
    }
    @Override
    public void start(Stage primaryStage) throws Exception {
        primaryStage.setScene(new Scene(getContent()));
        //primaryStage.setTitle(FXUtils.version());
        primaryStage.show();
    }
    
    public static void main(String[] args) {
        launch(args);
    }
    
    @SuppressWarnings("unused")
    private static final Logger LOG = Logger
            .getLogger(TablePCoreAddAndEdit.class.getName());
}