YAML

omnist::formats::yaml::{read_yaml, write_yaml, check_yaml}. Ported from ~/dev/omnist/omnist/formats.py’s read_yaml/write_yaml/check_yaml; see omnist/src/formats/yaml.rs’s module doc for the full detail.

#![allow(unused)]
fn main() {
use indexmap::IndexMap;
use omnist::document::{Doc, Value};
use omnist::formats::yaml::{read_yaml, write_yaml};

let mut fields = IndexMap::new();
fields.insert("name".to_string(), Value::Str("Ada".to_string()));
fields.insert("age".to_string(), Value::Int(37));
let doc = Doc::of(&Value::Object(fields)).unwrap();

let text = write_yaml(&doc, true, None).unwrap();
let doc2 = read_yaml(&text).unwrap();
assert!(doc.eq_doc(&doc2));
}

Scalar-tag resolution: PyYAML’s rules, not yaml_rust2’s

yaml_rust2’s own resolver only recognizes true/false for booleans (YAML 1.2 core schema). This module ignores that and re-implements PyYAML’s YAML-1.1 implicit-resolver regexes instead, live-checked against PyYAML (this project’s Python reference): yes/no/on/off (and case variants) are also booleans; bare y/n are not and stay strings. Quoted scalars are never auto-typed, matching PyYAML (implicit resolution only applies to plain-style scalars).

Merge keys (<<)

yaml_rust2 has no built-in merge-key support; this module implements the YAML merge-key spec directly (an unquoted << key’s value must be a mapping or sequence of mappings, merged in order, explicit keys taking precedence).

No native temporal type, but a looser input grammar than JSON

Like json.rs, Scalar has no temporal variant – a timestamp becomes a Scalar::Str holding its ISO spelling. Unlike JSON, YAML’s timestamp grammar is looser (space-separated date/time, single-digit month/day, a bare Z suffix, no zero-padding); this module normalizes any such spelling to the same canonical, zero-padded, T-joined ISO shape PyYAML’s own datetime.isoformat() would produce – so 2001-12-14 21:59:43.10 -5 round-trips to 2001-12-14T21:59:43.100000-05:00, not its original spelling. A timestamp-shaped string naming a calendar/clock value that doesn’t exist (2024-13-01) is a ParseError, matching PyYAML’s own construction-time failure.

Native NaN/Infinity – no lossy adjustment here (unlike JSON)

YAML’s float grammar has native .nan/.inf/-.inf tokens, so unlike write_json, write_yaml never substitutes null for a special float. The only adjustment check_yaml ever records is forcing double-quoted style for a string containing U+0085 (NEL), which PyYAML’s default styles would otherwise normalize away as a line break.

Integer digit cap

Same 4300-digit cap as json.rs/oml.rs/toml.rs, applied to a plain decimal integer scalar’s digit run before parsing; the same i64 representational ceiling applies (see formats/json.md).