Using should as function issue

[killmenot]

Hi,

When I use should the following way:

var sinon = require('sinon');
var should = require('should');
require('./should-sinon');

var callback = sinon.spy();
callback.should.not.be.called();

All works as expected. However, when I use should as function, the adapter works not as expected

var sinon = require('sinon');
var should = require('should/as-function');
require('./should-sinon');

var callback = sinon.spy();
should(callback)not.be.called(); // throws callback.called is not a function

The problem is that adapter use should by default here https://github.com/shouldjs/sinon/blob/master/should-sinon.js#L1-L9

[killmenot]

@btd

I have some ideas how to fix this issue but before creating a PR would like to know your thoughts about it.

1. The first idea is to switch from:

var sinon = require('sinon');
var should = require('should');
require('should-sinon');

to

var sinon = require('sinon');
var should = require('should');
require('should-sinon')(should);
// or
var sinon = require('sinon');
var should = require('should/as-function');
require('should-sinon')(should);

But, ofc, this is breaking change.

2. The second idea is to keep using current way but provide developers with ability to call shouldSinon adapter for custom object when it's needed.

// should-sinon
(function (factory) {
  if (typeof define === 'function' && define.amd) {
    define(['should'], factory);
  } else if (typeof exports === 'object') {
    module.exports = factory(require('should'));
  } else {
    factory(should);
  }
}(function (should) {
  function init (should) => {
     // initialization logic
  };
  
  init(should);
  
  return init;
});

// still work
var sinon = require('sinon');
var should = require('should');
require('should-sinon');

// this also will work
var sinon = require('sinon');
var should = require('should/as-function');
var shouldSinon = require('should-sinon');
shouldSinon(should);

WDYT?