Maintain RowGroup dataSrc when moved with ColReorder (#1121)

NEWS.md

@@ -1,5 +1,7 @@
 # CHANGES IN DT VERSION 0.32
 
+- Fixed a bug that caused the column used for grouping with the RowGroup extension to change when relocated by the ColReorder extension (thanks, @isthisthat, @mikmart, #1109).
+
 - Fixed the bug that `replaceData()` failed to work with data that has no column names (thanks, @mmuurr, #1108).
 
 - `updateSearch()` now sets the slider values based on the new search string for numeric columns (thanks, @mikmart, #1110).

inst/htmlwidgets/datatables.js

@@ -348,6 +348,15 @@ HTMLWidgets.widget({
     var table = $table.DataTable(options);
     $el.data('datatable', table);
 
+    if ('rowGroup' in options) {
+      // Maintain RowGroup dataSrc when columns are reordered (#1109)
+      table.on('column-reorder', function(e, settings, details) {
+        var oldDataSrc = table.rowGroup().dataSrc();
+        var newDataSrc = details.mapping[oldDataSrc];
+        table.rowGroup().dataSrc(newDataSrc);
+      });
+    }
+
     // Unregister previous Crosstalk event subscriptions, if they exist
     if (instance.ctfilterSubscription) {
       instance.ctfilterHandle.off("change", instance.ctfilterSubscription);