Schema modes

A schema decides how a plain scalar like NO, on, or 0123 becomes a typed value. saneyaml defaults to YAML 1.2, where those stay strings — so you don’t get the “Norway problem.”

The Norway problem

In YAML 1.1 (and the archived serde_yaml), NO resolves to the boolean false. A country-code list [NO, SE, FI] silently becomes [false, SE, FI].

YAML 1.2 fixed this: only true / false are booleans. saneyaml follows 1.2 by default.

#![allow(unused)]
fn main() {
let codes: Vec<String> = saneyaml::from_str("[NO, SE, FI]")?;
assert_eq!(codes, ["NO", "SE", "FI"]); // strings, as written
}

Default resolution (YAML 1.2)

The full table for every mode is in COMPATIBILITY.md → Scalar resolution.

Choosing a mode

Pass a configured LoadOptions instead of calling from_str directly:

#![allow(unused)]
fn main() {
use saneyaml::LoadOptions;

let cfg: Config = LoadOptions::core().from_str(text)?;          // YAML 1.2 (the default)
let cfg: Config = LoadOptions::json().from_str(text)?;          // JSON booleans/null/numbers only
let cfg: Config = LoadOptions::failsafe().from_str(text)?;      // every scalar stays a string
let cfg: Config = LoadOptions::legacy_serde_yaml().from_str(text)?; // YAML 1.1 / serde_yaml-style
}

Schema::{Core, Json, Failsafe, LegacySerdeYaml} are the enum equivalents; Schema::Yaml12 and Schema::Yaml11 are retained aliases for Core and LegacySerdeYaml.

Per-document %YAML directives

To let each document’s %YAML header pick the mode — %YAML 1.1 gets legacy construction, everything else stays 1.2 — use directive mode:

#![allow(unused)]
fn main() {
let docs = saneyaml::LoadOptions::yaml_version_directive().from_documents_str(stream)?;
}

What YAML 1.1 mode turns on

legacy_serde_yaml() / yaml_1_1() resolves the legacy forms: boolean words (yes/no/on/off), octal 0123, 0x/0b radix integers, base-60 sexagesimals, and !!timestamp-shaped scalars (read via saneyaml::Timestamp). Numeric spellings that overflow Number stay strings.

Even in YAML 1.2 mode you can still opt into individual YAML 1.1 types with explicit tags (!!int 0o77, !!binary …, !!timestamp …) without switching the whole schema. See COMPATIBILITY.md for the exact tag rules.