[Sskift]

With encoding: null or false, fields are Buffers. Combining either setting with rtrim: true or trim: true calls field.trimRight() on an unquoted field and throws a TypeError, even for ordinary CSV data.

Trim complete trailing whitespace byte sequences using the parser's existing whitespace table when decoding is disabled. Preserve the returned Buffer, including invalid UTF-8 bytes, and retain the existing behavior for quoted fields and decoded strings.

Validation:

• Four regressions fail before the fix, while two quoted-field controls already pass. All six pass afterward, including byte-sized stream chunks, Unicode whitespace, invalid UTF-8 and empty fields.
• csv-parse suite: 566 passing, two pending, excluding the existing Windows sample-path collection failure tracked in fix: resolve sample file URLs as native paths #512.
• TypeScript, changed-file ESLint/Prettier and git diff --check pass.

AI-assisted implementation and local verification using Codex.