stylelint/src/rules/color-hex-case/index.js

Modern CSS linter

import {
  report,
  ruleMessages,
  styleSearch,
  validateOptions,
} from "../../utils"

export const ruleName = "color-hex-case"

export const messages = ruleMessages(ruleName, {
  expected: (actual, expected) => `Expected "${actual}" to be "${expected}"`,
})

export default function (expectation) {
  return (root, result) => {
    const validOptions = validateOptions(result, ruleName, {
      actual: expectation,
      possible: [
        "lower",
        "upper",
      ],
    })
    if (!validOptions) { return }

    root.walkDecls(decl => {
      const declString = decl.toString()
      styleSearch({ source: declString, target: "#" }, match => {

        const hexMatch = /^#[0-9A-Za-z]+/.exec(declString.substr(match.startIndex))
        if (!hexMatch) { return }

        const hexValue = hexMatch[0]
        const hexValueLower = hexValue.toLowerCase()
        const hexValueUpper = hexValue.toUpperCase()
        const expectedHex = expectation === "lower" ? hexValueLower : hexValueUpper

        if (hexValue === expectedHex) { return }

        report({
          message: messages.expected(hexValue, expectedHex),
          node: decl,
          index: match.startIndex,
          result,
          ruleName,
        })
      })
    })
  }
}