setDataAtCell does not pass down source when changes are passed as array.
When we use the drag-fill and pass custome source from the setDataAtCell, We are still getting “edit” as source value.
In code snippet you will see a button below grid , when you click on the button you can see the source argument received by beforeChange and afterChnage in the console.
Please refer the code snippet : https://codepen.io/tbankar/pen/LYKwWpG