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Writing custom formatters

A formatter is a function with the following signature:

/**
 * @type {import('stylelint').Formatter}
 */
export default function formatter(results, returnValue) {
  return "a string of formatted results";
}

Where the first argument (results) is an array of Stylelint result objects (type Array<StylelintResult>).

And the second argument (returnValue) is an object (type LinterResult) with one or more of the following keys:

{
  "errored": false, // `true` if there were any warnings with "error" severity
  "maxWarningsExceeded": {
    // Present if Stylelint was configured with a `maxWarnings` count
    "maxWarnings": 10,
    "foundWarnings": 15
  },
  "ruleMetadata": {
    "block-no-empty": {
      "url": "https://stylelint.io/user-guide/rules/block-no-empty"
    }
    // other rules...
  }
}

Passing arguments​

You can use environmental variables in your formatter. For example, pass SKIP_WARNINGS:

SKIP_WARNINGS=true stylelint "*.css" --custom-formatter ./my-formatter.js

Alternatively, you can create a separate formatting program and pipe the output from the built-in JSON formatter into it:

stylelint -f json "*.css" 2>&1 | my-program-that-reads-JSON --option

stylelint.formatters​

Stylelint's internal formatters are exposed publicly in stylelint.formatters.

Sharing formatters​

Use the stylelint-formatter keyword within your package.json. For example:

{
  "keywords": ["stylelint", "stylelint-formatter"]
}