stylelint-scss/src/utils/hasInterpolatingAmpersand.js

A collection of SCSS specific rules for stylelint

import _ from "lodash"

/**
 * Check whether a selector has an interpolating ampersand
 * An "interpolating ampersand" is an "&" used to interpolate within another
 * simple selector (e.g. `&-modifier`), rather than an "&" that stands
 * on its own as a simple selector (e.g. `& .child`)
 *
 * @param {string} selector
 * @return {boolean} If `true`, the selector has an interpolating ampersand
 */
export default function (selector) {
  for (let i = 0; i < selector.length; i++) {
    if (selector[i] !== "&") { continue }
    if (!_.isUndefined(selector[i - 1]) && !isCombinator(selector[i - 1])) { return true }
    if (!_.isUndefined(selector[i + 1]) && !isCombinator(selector[i + 1])) { return true }
  }
  return false
}

function isCombinator(x) {
  return /[\s+>~]/.test(x)
}