Upgrading level to v2

Hi there, I’m upgrading from 1.7.0 to 2.1.2 at this small project and get the following error:

  Error {
    message: 'constructor requires a location string argument',
  }

  LevelDOWN.AbstractLevelDOWN (node_modules/leveldown/node_modules/abstract-leveldown/abstract-leveldown.js:12:11)
  new LevelDOWN (node_modules/leveldown/leveldown.js:14:21)
  LevelDOWN (node_modules/leveldown/leveldown.js:12:12)
  Level (node_modules/level-packager/level-packager.js:13:27)
  Object.create (test/helpers/database.js:11:18)
  Test.test.beforeEach.t [as fn] (test/validation.js:9:31)

Think because it’s missing the location parameter, at the following code: leveldb(process.env.LEVELDOWN_DB || require('memdown'));

How would I achieve this in version 2?

[Siilwyn]

Thank you all for your helpful & detailed responses! ❤️ Really like being able to swap out memdown and leveldown, perfect for testing.

If anybody is interested these are the changes I made to update: https://github.com/Siilwyn/cheers-receiver/pull/4/commits/242bd70fab78cc685a325ff981950c8e2cfba6fa

[ralphtheninja]

@Siilwyn I see now why it works

level@1.7.0 use level-packager@1.2.0 which does:

const levelup = require('levelup')

function packager (leveldown) {
  function Level (location, options, callback) {
    if (typeof options === 'function')
      callback = options
    if (!(typeof options === 'object' && options !== null))
      options  = {}

    options.db = leveldown

    return levelup(location, options, callback)
  }

  [ 'destroy', 'repair' ].forEach(function (m) {
    if (typeof leveldown[m] === 'function') {
      Level[m] = function (location, callback) {
        leveldown[m](location, callback || function () {})
      }
    }
  })

  return Level
}

module.exports = packager

Here location corresponds to { db: memdown } in your case, which is passed down to levelup() which will use that as a backend. Afaict this was not intended, but worked because levelup had this functionality.

Now level-packager does:

const levelup = require('levelup')
const encode = require('encoding-down')

function packager (leveldown) {
  function Level (location, options, callback) {
    if (typeof options === 'function') {
      callback = options
    }
    if (typeof options !== 'object' || options === null) {
      options = {}
    }

    return levelup(encode(leveldown(location), options), options, callback)
  }

  [ 'destroy', 'repair' ].forEach(function (m) {
    if (typeof leveldown[m] === 'function') {
      Level[m] = function (location, callback) {
        leveldown[m](location, callback || function () {})
      }
    }
  })

  Level.errors = levelup.errors

  return Level
}

module.exports = packager

Which is more unforgiving, since location really has to be a string.