getGroupingValue takes the original row only

[dvmoritzschoefl]

Currently, it seems that the code for getting the grouping value does this

  if (!column.columnDef.getGroupingValue) {
    return row.getValue(columnId)
  }

  if (row._groupingValuesCache) {
    row._groupingValuesCache[columnId] = column.columnDef.getGroupingValue(
      row.original,
    )
  }

which means it passes the original row only. Our problem is that we rely on accessor functions as data mapping mechanism, and this architecture prevents us from defining a custom groupingValue and an accessor function at the same time, since you need the row index (of the row, not the original) to call the accessor function.

We currently have a workaround involving a cache to make the values returned by the accessor function stable, but this seams suboptimal.

Would it be a useful addition for the table to pass the row instead of row.original or does this has some side effects i am not aware of?

[mg1986jp]

Yeah, this is a real limitation. getGroupingValue receives row.original because it was designed to compute grouping keys from raw data before the row model processes things like accessors. But if your accessor does non-trivial mapping (lookups, computed values), you end up duplicating that logic or maintaining a cache like you're doing.

The cleanest workaround without patching the library: compute the mapped values upfront and store them on the original data. Instead of relying on the accessor to do the mapping at render time, pre-process your data array before passing it to useReactTable:

const processedData = useMemo(() =>
  rawData.map((item, index) => ({
    ...item,
    _mappedValue: computeValue(item, index), // whatever your accessor does
  })),
  [rawData]
);

Then your getGroupingValue just reads row._mappedValue and the accessor reads the same field. Single source of truth, no cache needed.

If that doesn't fit your architecture (e.g. the mapping depends on other table state), then passing the full Row instead of row.original would be the right API change. It shouldn't cause issues since Row has .original on it anyway — existing code calling getGroupingValue(row.original) would just need to be updated to getGroupingValue(row) with users accessing row.original themselves. Might be worth opening a feature request / PR for that.