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Title: csv: support multi-character lineterminator in writer by jinmay · Pull Request #8328 · RustPython/RustPython · GitHub

Open Graph Title: csv: support multi-character lineterminator in writer by jinmay · Pull Request #8328 · RustPython/RustPython

X Title: csv: support multi-character lineterminator in writer by jinmay · Pull Request #8328 · RustPython/RustPython

Description: Closes #8322 This PR follows our AI policy Summary csv.writer rejected any lineterminator that was not a single character — including the default '\r\n' when passed explicitly — because the dialect stored it as a single-byte csv_core::Terminator. CPython accepts an arbitrary-length terminator. The dialect now stores the line terminator as an owned String (dropping PyDialect's Copy derive). The hand-written writer paths (QUOTE_MINIMAL / QUOTE_NONE / QUOTE_STRINGS / QUOTE_NOTNULL) emit the full terminator directly. The csv_core-backed QUOTE_ALL / QUOTE_NONNUMERIC paths still rely on csv_core for its quoting bookkeeping, so they emit a one-byte sentinel terminator (keeping csv_core's closing-quote / empty-record handling intact) and then replace that sentinel with the real terminator. field_needs_quotes / field_needs_escape now quote/escape a field containing any byte of the terminator, matching CPython. The reader now ignores lineterminator and always splits on \r / \n / \r\n, matching CPython (csv.reader never honored the dialect terminator) and avoiding a mid-UTF-8 record split that a multi-byte terminator would otherwise cause. import csv, io sio = io.StringIO() csv.writer(sio, lineterminator="!@#").writerow(["a", "b"]) # before: TypeError: "lineterminator" must be a 1-character string # after: 'a,b!@#' (matches CPython) Scoped to ASCII terminators; non-ASCII/surrogate terminators and empty-terminator acceptance are left for a follow-up. Test plan Unmarks test_write_lineterminator (@unittest.expectedFailure before). cargo run --release -- -m test test_csv: 128 run, 7 skipped, SUCCESS. extra_tests/snippets/stdlib_csv.py: passes (added test_multichar_lineterminator covering multi-char terminators, terminator-byte quoting, QUOTE_ALL / QUOTE_NONNUMERIC, QUOTE_NONE escaping, register_dialect round-trip, and reader behavior; verified on both RustPython and CPython). cargo fmt --check / cargo clippy: clean (no new warnings). Compared against CPython 3.14 on the same machine; the writer outputs match for ASCII terminators. Assisted-by: Claude Code:claude-opus-4-8 Summary by CodeRabbit Bug Fixes CSV dialects and lineterminator now support arbitrary non-empty multi-character line terminators. CSV writers emit the full configured terminator consistently across quoting modes, including QUOTE_NONE escaping. CSV readers reliably split records on \r\n, keeping any other terminator text as normal field content (CPython-aligned). Dialect registration and retrieval preserve the complete lineterminator value. Tests Added a snippet test for multi-character terminators covering multiple quoting modes, dialect round-tripping, and reader behavior.

Open Graph Description: Closes #8322 This PR follows our AI policy Summary csv.writer rejected any lineterminator that was not a single character — including the default '\r\n' when passed explicitly — because t...

X Description: Closes #8322 This PR follows our AI policy Summary csv.writer rejected any lineterminator that was not a single character — including the default '\r\n' when passed explicitly — b...

Opengraph URL: https://github.com/RustPython/RustPython/pull/8328

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