Module encoding/csv

CSV (RFC 4180) reader and writer.

A document is a list of records, a record a list of fields — Strings, byte-indexed like every other String. The reader accepts LF or CRLF record terminators, quoted fields ("...") with "" for an embedded quote and any bytes — delimiters, quotes, newlines — inside the quotes, and a final record with or without a terminator. The writer quotes a field only when it must (it contains the delimiter, a quote, CR or LF), so csv.parse(csv.write(rows)) round-trips.

Errors are a typed enum (CsvError) carrying byte positions, per the D1 convention for pure decoders (plans/archive/STD_API_AUDIT.md).

csv :: import("std/encoding/csv");
rows := csv.parse(String.from("a,b\n1,\"x,y\"\n"));   // Result(ArrayList(ArrayList(String)), CsvError)
text := csv.write(rows.unwrap());                      // `a,b\n1,"x,y"\n`

Stability

stable — frozen in #421, which reviewed the four expired unstable windows and decided this one. The whole module is eight names (csv_parse, csv_parse_with, csv_parse_strict, csv_write, csv_write_with, CsvOptions, LineEnding, CsvError), each covered by tests/encoding/csv.test.yo, and the shape questions a CSV reader has — whether a lenient parse or a strict one is the default, whether errors are values or effects, what a quote fault reports — are all answered and answered the way Rust's csv crate answers them.

There is deliberately NO header-record API: Reader::headers(), StringRecord and serde derive are the parts of Rust's csv this does not have, and adding them is ADDITIVE — a record here is an ArrayList(String) whether or not the first one names columns, so a future header layer sits on top of csv_parse without changing it. The one place to be careful is CsvOptions: it is a plain value struct with public fields, so a new option is a new field and every positional CsvOptions(...) literal names its fields — use default() or with_delimiter() and let new options default.

LineEnding.Lf as the writer default is the module's one divergence from RFC 4180 (which says CRLF) and is documented at default().