Contributing

Thanks for trying to contribute or interesting.

You can contribute to:

• Report any issues or bugs.
• Update schemas according to the updated specs of W3C/WHATWG.
• Request or propose something new function.
• Improve APIs and CLIs.
• Review to design for linting according to the specs.
• Improve the documentation and the website.
• Re-design and improve DevOps.
• Improve testing and coverage.
• Create and develop its plugins.

Its purpose is all developers are able to better markup and fit each of diverse their projects. So we want you to contribute. Your thought leads to diversity.

Code contribution

You need:

• Node.js v24 or later (the exact version is pinned in .mise.toml; install mise and run mise install to match it)
• Yarn 4.x (pinned in both .mise.toml and package.json#packageManager — bump them together; CI derives the sandbox Yarn version from the latter)

After cloning this repository, you can also install them through Docker.

When you wrote code then:

• Format and lint code through yarn lint.
• Check to build successfully through yarn build.
• Test your code through yarn test (this also runs TypeScript type-checking on spec files).
• Push to the topic branch and open a pull request.
• Assign reviewer:
  • For the improved code: @yusukehirao
  • For plugins: @yusukehirao
  • For documents/website: @yusukehirao, @kagankan

nu-validator compatibility benchmark

tests/external/ houses a local-only benchmark that compares markuplint with Nu Html Checker. It is not wired into CI. See tests/external/CLAUDE.md for the setup, command list, and the Docker / excluded-ids.json workflow.

Publishing the VS Code Extension

The npm packages are published automatically from CI (npm trusted publisher). The VS Code extension, in contrast, is published manually after the core packages land.

Publisher

The extension is published under the markuplint publisher (Marketplace ID: markuplint.vscode-markuplint).

The legacy yusukehirao.vscode-markuplint ID is deprecated from v5.0.0-rc.3 onwards and no longer receives updates.

yarn vscode:login runs vsce login markuplint, so the Azure DevOps Personal Access Token you authenticate with must have rights on the markuplint publisher.

Versioning

All packages — including the VS Code extension — share a single version because Lerna is configured in non-independent mode. The extension version therefore always matches the core version (e.g. 5.0.0, 5.0.0-rc.2).

VS Code's recommended odd/even minor split is not used. Instead, semver prerelease tags (-alpha.x / -beta.x / -rc.x) are mapped to the Marketplace prerelease channel.

When to publish which mode

Core version tag	Command	Marketplace channel
Stable (e.g. 5.0.0)	yarn vscode:release	Stable
-alpha.x / -beta.x / -rc.x	yarn vscode:pre-release	Prerelease

vscode:package / vscode:pre-package produce a local .vsix without publishing — use these for smoke-testing before running the publish commands.

Workflow

1. Wait for the core packages to be published to npm by CI
2. Pull the release tag locally (git pull --tags)
3. (First time only) yarn vscode:login to authenticate with Marketplace
4. Run yarn vscode:release or yarn vscode:pre-release depending on the tag (see the table above)

Valid modes accepted by vscode/scripts/install.mjs: package, release, pre-package, pre-release. Any other argument exits non-zero.

Reference

• VS Code: Prerelease Extensions
• @vscode/vsce