Migrating from `serde-yaml-ng` to `noyalib`

serde-yaml-ng (crate name serde_yaml_ng) is acatton’s independent continuation of serde_yaml. The README markets it as “as compatible as possible” with the original. 0.10.0 (2024-05-26) is the most recent release — actively maintained but the cadence is slow.

noyalib is a clean-room reimplementation of YAML 1.2 with the same serde data model, no unsafe code, and no libyaml C dependency.

Crates.io / docs.rs state verified 2026-09-05 (every function this guide names still exists on docs.rs). If the upstream API has shifted since, file an issue and we’ll update.

TL;DR

-[dependencies]
-serde_yaml_ng = "0.10"
+[dependencies]
+noyalib = "0.0"

-use serde_yaml_ng::Value;
-let v: Value = serde_yaml_ng::from_str(input)?;
-let s        = serde_yaml_ng::to_string(&v)?;
+use noyalib::Value;
+let v: Value = noyalib::from_str(input)?;
+let s        = noyalib::to_string(&v)?;

Function-by-function mapping

serde_yaml_ng mirrors serde_yaml 0.9 exactly.

`serde_yaml_ng` 0.10	`noyalib`
`serde_yaml_ng::from_str::<T>`	`noyalib::from_str::<T>`
`serde_yaml_ng::from_slice::<T>`	`noyalib::from_slice::<T>`
`serde_yaml_ng::from_reader::<R, T>`	`noyalib::from_reader::<R, T>`
`serde_yaml_ng::from_value::<T>`	`noyalib::from_value::<T>`
`serde_yaml_ng::to_string`	`noyalib::to_string`
`serde_yaml_ng::to_writer`	`noyalib::to_writer`
`serde_yaml_ng::to_value`	`noyalib::to_value`
`serde_yaml_ng::Value`	`noyalib::Value` (same 7 variants)
`serde_yaml_ng::Mapping`	`noyalib::Mapping`
`serde_yaml_ng::Number`	`noyalib::Number` (default `Integer` / `Float`; opt-in `Unsigned(u64)` behind `lossless-u64`)
`serde_yaml_ng::Error`	`noyalib::Error`
`serde_yaml_ng::Deserializer`	`noyalib::Deserializer`
`serde_yaml_ng::Serializer`	`noyalib::Serializer`
`serde_yaml_ng::with::singleton_map*`	`noyalib::with::singleton_map*`
(n/a)	`noyalib::from_str_strict::<T>` — error on unknown keys
(n/a)	`noyalib::Spanned<T>` — source-location wrapper
(n/a)	`noyalib::cst::Document` — lossless byte-faithful edits
(n/a)	`noyalib::ParserConfig` — explicit resource limits

serde_yaml_ng::Value is the same 7-variant enum: Null, Bool, Number, String, Sequence, Mapping, Tagged(Box<TaggedValue>). Match arms unchanged.

Behavioural differences worth knowing

The three notes that apply to the serde_yaml migration apply here. Full discussion in MIGRATION-FROM-SERDE-YAML.md; headlines:

Value::Tagged is preserved. from_str::<Value>("!Custom 'hi'\n") returns Value::Tagged(t) (t.tag() == "!Custom", t.value() == Value::String("hi")). serde_yaml_ng matched serde_yaml’s pre-Tagged behaviour; noyalib preserves the wrapper. Call .untag() to get the inner.
YAML 1.2 strict booleans by default. country: NO stays Value::String("NO"). Opt into YAML 1.1 boolean recognition via ParserConfig::new().legacy_booleans(true).
Multi-doc streams — use noyalib::load_all_as::<T>(input) for Vec<T> of every document in the stream.

Drop-in compatibility shim

[dependencies]
noyalib = { version = "0.0", features = ["compat-serde-yaml"] }

-use serde_yaml_ng::{from_str, to_string, Value, Mapping, Number};
+use noyalib::compat::serde_yaml::{from_str, to_string, Value, Mapping, Number};

The shim is a noyalib-native re-export under the compat::serde_yaml path; no transitive serde_yaml_ng dependency.

Migration checklist

Replace serde_yaml_ng = "0.10" → noyalib = "0.0" (or noyalib = { version = "0.0", features = ["compat-serde-yaml"] } for the shim path).
Replace use serde_yaml_ng::*; → use noyalib::*; (or use noyalib::compat::serde_yaml::*;).
If you exhaustively match Value, the 7-arm shape is unchanged.
Decide YAML 1.1-vs-1.2 boolean handling.
Run your existing test suite.

If you hit a snag, file an issue at https://github.com/sebastienrousseau/noyalib/issues.

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