proxyquireify/index.js

Proxies browserify's require in order to allow overriding dependencies during testing.

'use strict';

var fillMissingKeys = require('fill-keys');
var moduleNotFoundError = require('module-not-found-error');

function ProxyquireifyError(msg) {
  this.name = 'ProxyquireifyError';
  Error.captureStackTrace(this, ProxyquireifyError);
  this.message = msg || 'An error occurred inside proxyquireify.';
}

function validateArguments(request, stubs) {
  var msg = (function getMessage() {
    if (!request)
      return 'Missing argument: "request". Need it to resolve desired module.';

    if (!stubs)
      return 'Missing argument: "stubs". If no stubbing is needed, use regular require instead.';

    if (typeof request != 'string')
      return 'Invalid argument: "request". Needs to be a requirable string that is the module to load.';

    if (typeof stubs != 'object')
      return 'Invalid argument: "stubs". Needs to be an object containing overrides e.g., {"path": { extname: function () { ... } } }.';
  })();

  if (msg) throw new ProxyquireifyError(msg);
}

var stubs;

function stub(stubs_) {
  stubs = stubs_;
  // This cache is used by the prelude as an alternative to the regular cache.
  // It is not read or written here, except to set it to an empty object when
  // adding stubs and to reset it to null when clearing stubs.
  module.exports._cache = {};
}

function reset() {
  stubs = undefined;
  module.exports._cache = null;
}

var proxyquire = module.exports = function (require_) {
  if (typeof require_ != 'function')
    throw new ProxyquireifyError(
        'It seems like you didn\'t initialize proxyquireify with the require in your test.\n'
      + 'Make sure to correct this, i.e.: "var proxyquire = require(\'proxyquireify\')(require);"'
    );

  reset();

  return function(request, stubs) {

    validateArguments(request, stubs);

    // set the stubs and require dependency
    // when stub require is invoked by the module under test it will find the stubs here
    stub(stubs);
    var dep = require_(request);
    reset();

    return dep;
  };
};

// Start with the default cache
proxyquire._cache = null;

proxyquire._proxy = function (require_, request) {
  function original() {
    return require_(request);
  }

  if (!stubs || !stubs.hasOwnProperty(request)) return original();

  var stub = stubs[request];

  if (stub === null) throw moduleNotFoundError(request)

  var stubWideNoCallThru = Boolean(stubs['@noCallThru']) && (stub == null || stub['@noCallThru'] !== false);
  var noCallThru = stubWideNoCallThru || (stub != null && Boolean(stub['@noCallThru']));
  return noCallThru ? stub : fillMissingKeys(stub, original());
};

if (require.cache) {
  // only used during build, so prevent browserify from including it
  var replacePreludePath = './lib/replace-prelude';
  var replacePrelude = require(replacePreludePath);
  proxyquire.browserify = replacePrelude.browserify;
  proxyquire.plugin = replacePrelude.plugin;
}