A pure Effect-based YAML 1.2 parser, stringifier, and toolkit for TypeScript. Zero runtime dependencies beyond Effect — no wrappers, no ports, just a clean-room YAML 1.2 implementation designed for the Effect ecosystem.

• Parse and stringify YAML 1.2 with typed errors via Effect
• Bidirectional Effect Schema integration for validated YAML-to-domain roundtrips
• Non-destructive formatting, path-based modification, and semantic equality
• Stream-based lexer, CST parser, and visitor APIs for low-level processing
• Pipeline-friendly dual-style APIs (direct and pipe)

If you just need to parse YAML into a JavaScript object, use yaml. It is depended upon by 13,000+ packages, is battle-tested, and covers the full YAML 1.2 specification.

This library is for Effect-based programs that need deeper introspection and manipulation of YAML documents: typed parse errors you can catchTag, Schema pipelines that validate YAML strings into domain types, AST and CST access, non-destructive formatting and path-based modification, semantic equality comparisons, and SAX-style visitor streams that are composable in Effect pipelines.

Note: yaml-effect is new and may introduce breaking changes before a 1.0.0 release. We are actively working toward full YAML 1.2 spec compliance. The library is validated against the official yaml-test-suite — our current compliance is tracked in the badges above. The parser handles common YAML well, but edge cases around tab handling, complex mapping keys, and strict error rejection are still being addressed.

npm install yaml-effect effect

Peer dependency: effect (>= 3.x) must be installed alongside yaml-effect.

import { Effect } from "effect"; import { parse, stringify } from "yaml-effect"; const program = Effect.gen(function* () { const value = yield* parse("name: Alice\nage: 30"); console.log(value); // { name: "Alice", age: 30 } const yaml = yield* stringify({ greeting: "hello", count: 42 }); console.log(yaml); // "greeting: hello\ncount: 42\n" }); Effect.runSync(program);

For API reference, configuration options, and advanced usage, see docs.

MIT