stylelint/src/rules/at-rule-name-space-after/index.js

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

export const ruleName = "at-rule-name-space-after"

export const messages = ruleMessages(ruleName, {
  expectedAfter: (name) => `Expected single space after at-rule name \"${name}\"`,
})

export default function (expectation) {
  const checker = whitespaceChecker("space", expectation, messages)
  return (root, result) => {
    const validOptions = validateOptions(result, ruleName, {
      actual: expectation,
      possible: [
        "always",
        "always-single-line",
      ],
    })
    if (!validOptions) { return }

    atRuleNameSpaceChecker({
      root,
      result,
      locationChecker: checker.after,
      checkedRuleName: ruleName,
    })
  }
}

export function atRuleNameSpaceChecker({ locationChecker, root, result, checkedRuleName }) {
  root.walkAtRules(atRule => {
    if (!isStandardSyntaxAtRule(atRule)) { return }

    checkColon(
      `@${atRule.name}${atRule.raws.afterName}${atRule.params}`,
      atRule.name.length,
      atRule
    )
  })

  function checkColon(source, index, node) {
    locationChecker({
      source,
      index,
      err: m => report({
        message: m,
        node,
        index,
        result,
        ruleName: checkedRuleName,
      }),
      errTarget: `@${node.name}`,
    })
  }
}