ryl 0.15.0

Fast YAML linter inspired by yamllint

ryl

ryl - the Rust YAML linter - is intended to ultimately be a drop-in replacement for yamllint. It is usable today, but parity and edge-case behaviour are still maturing.

Full documentation lives at https://ryl-docs.pages.dev/.

Compatibility note

• ryl aims to match yamllint behaviour and includes many parity tests.
• ryl uses the granit-parser parser stack, while yamllint uses the PyYAML parser stack.
• granit-parser and PyYAML do not always agree on which files are valid YAML.
• ryl targets YAML 1.2 strictly. yamllint defaults to YAML 1.1 semantics, so bareword booleans like yes / no / on / off (and case variants) are plain strings in ryl and booleans in yamllint. Leading-zero integers like 0755 are decimal in ryl and octal in yamllint. The same 1.2 semantics also apply when ryl parses .yamllint configuration files inherited from yamllint. See the YAML version compatibility page for the practical implications.

Quick start

ryl enables no rules by default, so it needs a configuration that turns rules on. -d 'extends: default' opts into yamllint's standard rule set for a one-off run; for a project, drop a .ryl.toml at the root (see Configuration).

# Using uv (Python)
uvx ryl -d 'extends: default' .

# Using npx (Node.js)
npx @owenlamont/ryl -d 'extends: default' .

For prek / pre-commit integration, see ryl-pre-commit.

Installation

uv tool install ryl                 # uv
npm install -g @owenlamont/ryl      # npm
pip install ryl                     # pip
cargo install ryl                   # cargo

Status and scope

• All 23 yamllint rules are implemented, plus a ryl-only tags rule (forbids unsafe and non-portable YAML tags; configured in TOML only). The current rule reference and per-rule pages are at https://ryl-docs.pages.dev/rules/.
• Auto-fixing (--fix) is supported for braces, brackets, commas, comments, comments-indentation, new-line-at-end-of-file, new-lines, and quoted-strings. The set of rules that may apply fixes is configurable via the TOML [fix] table.
• --diff previews those safe fixes as a unified diff on stdout instead of writing them (modelled on ruff check --diff); it is mutually exclusive with --fix, works with stdin, and exits 1 iff some file would change.
• TOML is the recommended configuration format and supports ryl-only features that have no upstream equivalent: the [fix] table, [per-file-ignores], and rule options such as allow-double-quotes-for-escaping.
• TOML assigns each file a source kind via the [files] table (yaml = [...], markdown = [...]). The legacy yaml-files key is YAML-only; in TOML use [files].yaml.
• YAML embedded in Markdown (front matter and fenced yaml/yml blocks) can be linted by listing globs under [files].markdown; diagnostics map back to the Markdown file. It is off by default; --fix writes safe fixes back into the embedded blocks and --diff previews them at the host-file level. See https://ryl-docs.pages.dev/markdown/.
• yamllint-style YAML configuration is also accepted (.yamllint, .yamllint.yml, .yamllint.yaml) for drop-in compatibility, including the built-in default, relaxed, and empty presets via extends. An existing yamllint configuration can be converted with ryl --migrate-configs --migrate-write.
• --list-files prints the files ryl would lint (after ignores and config discovery) and exits, without running rules. --no-warnings suppresses warning-level diagnostics in the output. --strict turns a warning-only run into exit code 2.
• Pass - as the input to read YAML from stdin (ruff convention). Add --stdin-filename <PATH> so diagnostics, project-config discovery, and path-based filtering (yaml-files, per-file-ignores, per-rule ignore) use that filename. Without it, diagnostics are labelled <stdin>, config is anchored at the current working directory, and all path-based filtering is skipped so every enabled rule runs. - cannot be combined with other inputs; --fix cannot read from stdin, but --diff can.
• Run ryl --help for the authoritative CLI reference.

For installation walkthroughs, configuration presets, and per-rule documentation, see the docs site.

Performance

ryl is significantly faster than yamllint on large trees. The figure below is from a 5x5 file-count × file-size matrix with 5 runs per point:

The benchmark script is in scripts/benchmark_perf_vs_yamllint.py; run it with --help for the full option set.

Acknowledgements

This project exists thanks to the tooling and ecosystems around YAML linting and developer automation, especially:

• yamllint - for giving me the shoulders to stand on and the source of many of the automated tests that ryl uses now to check for behaviour parity. Copying the behaviour of an existing tool is infinitely easier than building one from scratch - there'd be no ryl without yamllint.
• ruff - for showing the power of Rust tooling for Python development and inspiring the config and API for ryl.
• rumdl - for giving me another template to follow for Rust tooling and showing me almost the only dev tool I was still using after this that wasn't written in Rust was yamllint (which inspired me to tackle this project).
• saphyr - ryl's vendored YAML DOM is derived from saphyr, and saphyr's developers were very patient in showing some of the nuance and complexity of parsing YAML which I was embarrassingly ignorant of when starting ryl.
• granit-parser - a saphyr-parser fork with comment and style metadata that ryl uses for event-stream parsing.
• esbuild and biome - for providing the "binary wrapper" blueprint for distributing high-performance native tools via NPM.