url.format/querystring.stringify include undefined parameters in querystring

[punmechanic]

url.format (on node 0.12.0, which in turn calls querystring.stringify) will include parameters on an object that are explicitly undefined. If you don't want to read the real life consequences, here's some example code demonstrating the issue - just skip to the bottom.

Dan@DAN-PC ~
$ node
> var querystring = require('querystring');
undefined
> querystring.stringify({foo:undefined})
'foo='

Using an excerpt from the library I am developing:

  function all(region, freeToPlayOnly) {
    return riot.get(region, version, 'champion', {
      freeToPlay: freeToPlayOnly
    });
  }

If I do not pass in freeToPlayOnly to all(), then obviously it will be undefined. The object passed to riot.get will, therefore, be { freeToPlay: undefined }. Inside riot.get, the following code is invoked:

  function get(region, version, path, queryParameters) {
    var myUrl = url.format({
      host: util.format(base, region),
      protocol: 'http',
      pathname: util.format(pathFormat, region, version, path),
      query: queryParameters
    });

    // the following is example code
    return http.get(myUrl);
  }

As you can see from the above code, our { freeToPlay: undefined } is passed to the get function as queryParameters, which are then passed to query.

If you invoke this method and examine myUrl, it will be host/pathname?freeToPlay=. In my opinion, this is incorrect - I would have expected to have received host/pathname back (as the value of freeToPlay is undefined). The current behaviour would make sense if I explicitly passed null to the url.format method, but I did not.

Hope i've explained this well enough.

[cjihrig]

FWIW, this has been proposed and rejected before (see #7971).