metamask-extension/app/scripts/migrations/026.js

/*

This migration moves the identities stored in the KeyringController
 into the PreferencesController

*/

import { cloneDeep } from 'lodash'

const version = 26

export default {
  version,
  migrate(originalVersionedData) {
    const versionedData = cloneDeep(originalVersionedData)
    versionedData.meta.version = version
    try {
      const state = versionedData.data
      versionedData.data = transformState(state)
    } catch (err) {
      console.warn(`MetaMask Migration #${version}${err.stack}`)
      return Promise.reject(err)
    }
    return Promise.resolve(versionedData)
  },
}

function transformState(state) {
  if (!state.KeyringController || !state.PreferencesController) {
    return state
  }

  if (!state.KeyringController.walletNicknames) {
    return state
  }

  state.PreferencesController.identities = Object.keys(
    state.KeyringController.walletNicknames,
  ).reduce((identities, address) => {
    identities[address] = {
      name: state.KeyringController.walletNicknames[address],
      address,
    }
    return identities
  }, {})
  delete state.KeyringController.walletNicknames
  return state
}