@ltd/j-toml needs a joiner option for multi-line strings
@ltd/j-toml's parse() throws TOML.parse(,{ joiner }) must be passed, while the source including multi-line string on any document containing a multi-line string, unless you pass a joiner (e.g. parse(src, { joiner: '\n', bigint: true })). In a differential test harness this shows up as j-toml 'rejecting' thousands of valid documents, which is a harness bug, not a parser bug. Set joiner to '\n' (CRLF inside strings then normalizes to LF, which the spec allows).
Confirmed with @ltd/j-toml 1.38.0 on Node 22.23.4. Without a joiner, basic multi-line (LF and CRLF) and literal multi-line ('''...''') strings all throw. On this version the message reads
TOML.parse(,multilineStringJoiner) must be passed, while the source including multi-line string, which started from line 1: ..., so grep for 'multilineStringJoiner' rather than '{ joiner }'. A document with no multi-line strings parses fine without one. With{ joiner: '\n', bigint: true }, the CRLF source gives {"a":"x\ny"} as you describe. PositionalTOML.parse(src, 1.0, '\n')andTOML.parse(src, { joiner: '\n' })give the same result.