Round-trip & fmt –check

Problem. You want to confirm a file is already in canonical Aozora form — or to canonicalise it — and to rely on parse ∘ serialize being lossless.

The property

AozoraTree::serialize re-emits Aozora source from the parsed tree. The guarantee is a fixed point: parsing a canonical document and serialising it returns the same bytes, and serialising again changes nothing.

use aozora::Document;

fn main() {
    let source = "｜青梅《おうめ》";

    let once = Document::new(source).parse().serialize();
    let twice = Document::new(once.clone()).parse().serialize();

    assert_eq!(once, twice, "serialize is a fixed point");
    println!("{twice}");
}

Expected output

｜青梅《おうめ》

Canonical vs. raw input

Real Aozora Bunko sources carry stylistic variation the lexer normalises before tokenising — CRLF vs LF, NFC vs NFD around accents, and the bare-vs-explicit ruby delimiter (青梅《おうめ》 vs ｜青梅《おうめ》). For raw input, therefore:

// Not guaranteed for arbitrary raw input:
assert_eq!(Document::new(raw).parse().serialize(), raw);   // may differ

// Guaranteed: the SECOND pass is a fixed point.
let canonical = Document::new(raw).parse().serialize();
assert_eq!(Document::new(canonical.clone()).parse().serialize(), canonical);

The first serialize() is the canonical form (e.g. it always emits the explicit ｜ ruby delimiter — see the Ruby node chapter); from there it is stable. This fixed-point property is what the corpus sweep verifies across the full ~17 000-work catalogue.

Solution (CLI)

aozora fmt is the round-trip at the shell. With --check it is a read-only gate — exit 0 if the file is already canonical, 1 if it would change:

aozora fmt --check src.txt        # CI gate: nonzero if not canonical
aozora fmt src.txt > out.txt      # write the canonical form to stdout
aozora fmt --write src.txt        # rewrite in place
cat src.txt | aozora fmt          # stdin → stdout

Exit codes: 0 on success (or no diff under --check), 1 on a formatting mismatch under --check, 2 on a usage error. aozora fmt --check is exactly what this project runs in CI to keep fixtures canonical.

See also

• Runnable example: just example round_trip (crates/aozora/examples/round_trip.rs).
• Library Quickstart → Round-trip.
• HTML renderer & canonical serialiser — how the canonical form is defined.
• CLI reference → aozora fmt — flags and exit codes.