A formula read with `cm` (Excel's XLDAPR dynamic-array record in
xl/metadata.xml) now carries `Formula::dynamic`, and the writer keeps the
`cm` and the metadata part for it even when the formula returns one value
and the export shape analysis would not need array evaluation. Before, such
formulas were saved as legacy formulas, so Excel recalculated some of them
with implicit intersection (SUMPRODUCT(IFERROR(range/range,0)) changed
value), and workbooks whose every dynamic formula was scalar lost
xl/metadata.xml altogether.
The mark survives moves, row and column insertion or deletion, sheet and
name renames and LAMBDA call-case fixes; retyping a formula drops it and
the writer decides from the formula's shape, as before. It is serialized
only when set, so saved documents without it are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
write_csv visited every position of the used range and appended to one growing
String with no limit, so two cells far apart (A1 and XFD1048576) asked for
about 16 GiB of commas. The output is now capped at 512 MiB: a lower bound
(delimiters and line ends of every row) is checked before anything is
allocated, and the text written so far is checked after each row. Over the
cap, write_csv returns IoError::TooLarge naming the rows, columns and limit,
and Save As / Export CSV and TSV report it without writing a file. Accepted
exports are unchanged. write_csv now returns a Result.
