Sparse cell values — the same encoding ISheet.JSON.data uses (ICell.JSON is already just
the value+type pair; style/formula live in sibling fields there, none of which apply to a
values-only cache — design doc §2.5).
OptionalrefreshError
refreshError?:boolean
<sheetData refreshError="1"> — Excel could not refresh this sheet's cache last time it tried.
Sparse cell values — the same encoding
ISheet.JSON.datauses (ICell.JSONis already just the value+type pair; style/formula live in sibling fields there, none of which apply to a values-only cache — design doc §2.5).