PureYAML

PureYAML is a dependency-free YAML package written entirely in Swift.

The goal is a Linux- and WebAssembly-compatible replacement for the YAML pieces that currently force packages such as OpenAPIDoctor through C-backed parsers. The package is intentionally strict about portability:

no external SwiftPM dependencies
no bundled C sources
no Foundation requirement in the library target
root Swift package layout
macOS, Linux, and WASI build gates

Status

This repository starts with the first real parser milestone: block mappings, block sequences, ordered mappings, common scalars, quoted strings, comments, and a matching dumper. It also includes path-aware validation for structural YAML checks such as duplicate mapping keys.

It is not yet a full YAML 1.2 implementation. Anchors, aliases, tags, flow collections, folded scalars, literal scalars, directives, and custom decoding are planned work.

Attribution

PureYAML is informed by Yams and its bundled CYaml / libyaml-derived parser, but it does not copy their implementation into Sources/. See ATTRIBUTION.md.

Usage

import PureYAML

let document = try PureYAML.parse("""
openapi: 3.1.0
info:
  title: Example API
servers:
  - url: /
""")

let yaml = PureYAML.dump(document)

try PureYAML.validate(document)

Development Contract

PureYAML must stay dependency-free and portable. Before merging changes:

bash scripts/check-style.sh
bash scripts/check-namespacing.sh
bash scripts/check-changelog-touched.sh
swiftformat . --config .swiftformat --lint
swiftlint --config .swiftlint.yml --strict
swift build
swift test
bash scripts/check-linux.sh
bash scripts/check-wasm.sh

scripts/check-wasm.sh expects a Swift toolchain with a matching Swift Wasm SDK. For Swift 6.3.2, install the SDK with:

swift sdk install https://download.swift.org/swift-6.3.2-release/wasm-sdk/swift-6.3.2-RELEASE/swift-6.3.2-RELEASE_wasm.artifactbundle.tar.gz --checksum a61f0584c93283589f8b2f42db05c1f9a182b506c2957271402992655591dd7c

License

MIT.

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