vuepress/packages/@vuepress/shared-utils/lib/module.js

// Midified from https://github.com/vuejs/vue-cli/blob/dev/packages/@0vue/cli-shared-utils/lib/module.js

const semver = require('semver')
const path = require('upath')
const fs = require('fs-extra')
const { isTest } = require('./env')

function resolveFallback (request, options) {
  const Module = require('module')
  const isMain = false
  const fakeParent = new Module('', null)

  const paths = []

  for (let i = 0; i < options.paths.length; i++) {
    const path = options.paths[i]
    fakeParent.paths = Module._nodeModulePaths(path)
    const lookupPaths = Module._resolveLookupPaths(request, fakeParent, true)

    if (!paths.includes(path)) paths.push(path)

    for (let j = 0; j < lookupPaths.length; j++) {
      if (!paths.includes(lookupPaths[j])) paths.push(lookupPaths[j])
    }
  }

  const filename = Module._findPath(request, paths, isMain)
  if (!filename) {
    const err = new Error(`Cannot find module '${request}'`)
    err.code = 'MODULE_NOT_FOUND'
    throw err
  }
  return filename
}

const resolve = semver.satisfies(process.version, '>=10.0.0')
  ? require.resolve
  : resolveFallback

exports.resolveModule = function (request, context) {
  let resolvedPath
  // TODO
  // Temporary workaround for jest cannot resolve module path from '__mocks__'
  // when using 'require.resolve'.
  if (isTest() && request !== '@vuepress/theme-default') {
    resolvedPath = path.resolve(__dirname, '../../../../__mocks__', request)
    if (!fs.existsSync(`${resolvedPath}.js`) && !fs.existsSync(`${resolvedPath}/index.js`)) {
      throw new Error(`Cannot find module '${request}'`)
    }
    return resolvedPath
  }
  resolvedPath = resolve(request, {
    paths: [context || process.cwd()]
  })
  return resolvedPath
}

exports.loadModule = function (request, context, force = false) {
  const resolvedPath = exports.resolveModule(request, context)
  if (resolvedPath) {
    if (force) {
      clearRequireCache(resolvedPath)
    }
    return require(resolvedPath)
  }
}

exports.clearModule = function (request, context) {
  const resolvedPath = exports.resolveModule(request, context)
  if (resolvedPath) {
    clearRequireCache(resolvedPath)
  }
}

function clearRequireCache (id, map = new Map()) {
  const module = require.cache[id]
  if (module) {
    map.set(id, true)
    // Clear children modules
    module.children.forEach(child => {
      if (!map.get(child.id)) clearRequireCache(child.id, map)
    })
    delete require.cache[id]
  }
}