PostCSS Runner Guidelines
A PostCSS runner is a tool that processes CSS through a user-defined list of plugins; for example, postcss-cli
or gulp‑postcss
. These rules are mandatory for any such runners.
For single-plugin tools, like gulp-autoprefixer
, these rules are not mandatory but are highly recommended.
See also ClojureWerkz’s recommendations for open source projects.
1. API
1.1. Accept functions in plugin parameters
If your runner uses a config file, it must be written in JavaScript, so that it can support plugins which accept a function, such as postcss-assets
:
2. Processing
2.1. Set from
and to
processing options
from
and to
processing optionsTo ensure that PostCSS generates source maps and displays better syntax errors, runners must specify the from
and to
options. If your runner does not handle writing to disk (for example, a gulp transform), you should set both options to point to the same file:
2.2. Use only the asynchronous API
PostCSS runners must use only the asynchronous API. The synchronous API is provided only for debugging, is slower, and can’t work with asynchronous plugins.
2.3. Use only the public PostCSS API
PostCSS runners must not rely on undocumented properties or methods, which may be subject to change in any minor release. The public API is described in API docs.
3. Output
3.1. Don’t show JS stack for CssSyntaxError
CssSyntaxError
PostCSS runners must not show a stack trace for CSS syntax errors, as the runner can be used by developers who are not familiar with JavaScript. Instead, handle such errors gracefully:
3.2. Display result.warnings()
result.warnings()
PostCSS runners must output warnings from result.warnings()
:
See also postcss-log-warnings and postcss-messages plugins.
3.3. Allow the user to write source maps to different files
PostCSS by default will inline source maps in the generated file; however, PostCSS runners must provide an option to save the source map in a different file:
4. Documentation
4.1. Document your runner in English
PostCSS runners must have their README.md
wrote in English. Do not be afraid of your English skills, as the open source community will fix your errors.
Of course, you are welcome to write documentation in other languages; just name them appropriately (e.g. README.ja.md
).
4.2. Maintain a changelog
PostCSS runners must describe changes of all releases in a separate file, such as ChangeLog.md
, History.md
, or with GitHub Releases. Visit Keep A Changelog for more information on how to write one of these.
Of course, you should use SemVer.
4.3. postcss-runner
keyword in package.json
postcss-runner
keyword in package.json
PostCSS runners written for npm must have the postcss-runner
keyword in their package.json
. This special keyword will be useful for feedback about the PostCSS ecosystem.
For packages not published to npm, this is not mandatory, but recommended if the package format is allowed to contain keywords.
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