text: 'use strict'
  module.exports = isOptional
  
  const isOptDep = require('./is-opt-dep.js')
  const moduleName = require('../utils/module-name.js')
  
  function isOptional (node, seen) {
    if (!seen) seen = new Set()
    // If a node is not required by anything, then we've reached
    // the top level package.
    if (seen.has(node) || node.requiredBy.length === 0) {
      return false
    }
    seen = new Set(seen)
    seen.add(node)
    const swOptional = node.fromShrinkwrap && node.package._optional
    return node.requiredBy.every(function (req) {
      if (req.fakeChild && swOptional) return true
      return isOptDep(req, moduleName(node)) || isOptional(req, seen)
    })
  }
  