metamask-extension/app/scripts/migrations/002.js

import { cloneDeep } from 'lodash'

const version = 2

export default {
  version,

  migrate (originalVersionedData) {
    const versionedData = cloneDeep(originalVersionedData)
    versionedData.meta.version = version
    try {
      if (versionedData.data.config.provider.type === 'etherscan') {
        versionedData.data.config.provider.type = 'rpc'
        versionedData.data.config.provider.rpcTarget = 'https://rpc.metamask.io/'
      }
    } catch (_) {
      // empty
    }
    return Promise.resolve(versionedData)
  },
}