[plugins] Allow empty plugin add method call

Allow the general plugin add method to be called
with an empty object.
import * as config from './config'
import * as dict from '../get/dict'
import * as input from '../parse/interface/register'
import * as output from '../get/registrar'

const getConfig = config.get
const registers = {
  config,
  dict,
  input,
  output
}

const indices = {}

export const add = (ref, plugins = {}) => {
  let mainIndex = indices[ref] = {}

  if ('config' in plugins) {
    registers.config.add(ref, plugins.config)
    delete plugins.config
  }

  for (let type in plugins) {
    let typeIndex = mainIndex[type] = {}
    let typePlugins = plugins[type]

    for (let name in typePlugins) {
      let typePlugin = typePlugins[name]

      typeIndex[name] = true
      registers[type].add(name, typePlugin)
    }
  }
}

export const remove = (ref) => {
  let mainIndex = indices[ref]

  for (let type in mainIndex) {
    let typeIndex = mainIndex[type]

    for (let name in typeIndex) {
      registers[type].remove(name)
    }
  }

  delete indices[ref]
}

export const has = (ref) => ref in indices
export const list = () => Object.keys(indices)

export {getConfig as config, registers}

import * as config from './config'
import * as dict from '../get/dict'
import * as input from '../parse/interface/register'
import * as output from '../get/registrar'

const getConfig = config.get
const registers = {
  config,
  dict,
  input,
  output
}

const indices = {}

export const add = (ref, plugins) => {
  let mainIndex = indices[ref] = {}

  if ('config' in plugins) {
    registers.config.add(ref, plugins.config)
    delete plugins.config
  }

  for (let type in plugins) {
    let typeIndex = mainIndex[type] = {}
    let typePlugins = plugins[type]

    for (let name in typePlugins) {
      let typePlugin = typePlugins[name]

      typeIndex[name] = true
      registers[type].add(name, typePlugin)
    }
  }
}

export const remove = (ref) => {
  let mainIndex = indices[ref]

  for (let type in mainIndex) {
    let typeIndex = mainIndex[type]

    for (let name in typeIndex) {
      registers[type].remove(name)
    }
  }

  delete indices[ref]
}

export const has = (ref) => ref in indices
export const list = () => Object.keys(indices)

export {getConfig as config}
export {registers}
