📝 Scope the round-trip byte-for-byte promise to UTF-8#209
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YAMLRocks reads UTF-16 and UTF-32 (the YAML spec requires it, detected by a byte order mark or the leading-byte pattern), but it decodes to text internally and re-emits as UTF-8. So a UTF-16 file loads to the right data, yet re-emitting it under OPT_ROUND_TRIP produces that text as UTF-8, not the original UTF-16 bytes. The byte-for-byte guarantee only ever meant UTF-8, which is what configuration files use in practice. Say so in the round-trip guide and the stability roadmap, rather than imply an encoding-preserving round-trip we do not offer. No behavior change; this documents what already happens.
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Pull request overview
This documentation-only PR clarifies that YAMLRocks's round-trip "byte-for-byte" guarantee applies only to UTF-8 input. YAMLRocks reads UTF-16/UTF-32 (per the YAML 1.2 spec, detected by BOM or null-byte pattern) but transcodes them to UTF-8 internally, so re-emitting a non-UTF-8 file produces the same text as UTF-8 rather than the original bytes. The change adds this scope to the two most prominent contract pages (the round-trip guide and the stability roadmap) without altering any code behavior. I verified the claims against detect_encoding/bytes_to_string in src/ffi/mod.rs and the UTF-8-only real-world corpus filter — both accurately support the documented behavior.
Changes:
- Adds a
:::note[Byte fidelity is a UTF-8 guarantee]block to the round-trip guide explaining the UTF-16/UTF-32 transcoding behavior and advising UTF-8 conversion for byte-for-byte editing. - Qualifies the stability roadmap's "Round-trip preservation" contract to specify an unmodified UTF-8 document re-emits byte-for-byte.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| docs/src/content/docs/guides/round-trip.md | Adds a note scoping the byte-for-byte promise to UTF-8 and describing UTF-16/32 transcoding. |
| docs/src/content/docs/stability-roadmap.md | Qualifies the round-trip preservation contract to UTF-8, noting UTF-16/32 re-emit as UTF-8. |
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #209 +/- ##
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+ Coverage 92.56% 93.07% +0.51%
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Files 40 40
Lines 12051 12672 +621
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+ Hits 11155 11795 +640
+ Misses 896 877 -19 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Breaking change
None. Documentation only, no behavior change.
Proposed change
YAMLRocks reads UTF-16 and UTF-32 (the YAML 1.2 spec requires it, detected by a byte order mark or the leading-byte pattern), but it decodes to text internally and re-emits as UTF-8. So a UTF-16 file loads to the right data, yet re-emitting it under
OPT_ROUND_TRIPproduces that text as UTF-8, not the original UTF-16 bytes.The byte-for-byte guarantee only ever meant UTF-8, which is what configuration files use in practice. This scopes the claim explicitly in the two places that make it, the round-trip guide and the stability roadmap, rather than imply an encoding-preserving round-trip that is not offered. It documents current behavior; nothing changes in code.
Context: the yamlrocks-vs-PyYAML round-trip differential surfaced UTF-16 inputs as non-byte-identical on re-emit. That is expected (transcoding to UTF-8), so the fix is to state the guarantee's scope, not to change the round-trip.
Type of change
Additional information
Checklist
uv run pytestpasses locally. A pull request cannot be merged unless CI is green.uv run ruff check .anduv run ruff format --check .pass.cargo fmt --checkandcargo clippy --all-targets -- -D warningspass.If the change is user-facing:
docs/is added or updated, anddocs/verify_examples.pystill passes.