Mechanize #post does not retain order of fields defined

[jasonwbarnett]

I'm working on a project where the order of which fields are passed to the query is crucial. I was trying to build something and realized that the order was not retained. I believe it only happens when one of the fields contains bracket in it, i.e.

field name: rsargs[]
field value: anything

Code to reproduce the problem: https://gist.github.com/jasonwbarnett/249aa44a0e2b3ac078fe

I know that a lot of the code probably makes no sense (nor does the server response), but it conveys the problem quite well.

Version Info:
Mechanize/2.6.0
Ruby/1.9.3p392

[ryansch]

I just hit my head on this in phillbaker/capybara-mechanize#52.

[ryansch]

My analysis points to https://github.com/sparklemotion/mechanize/blob/master/lib/mechanize/form.rb#L259 as the source of the problem. Mechanize seems to go out of its way to define a custom sorting for fields (https://github.com/sparklemotion/mechanize/blob/master/lib/mechanize/form/field.rb#L39). Why is this?

[drbrain]

The sort in mechanize/form.rb is designed to keep the fields in the order they appear in the document and the case of a generic POST as in your example was not considered.

I think this can be fixed by altering Mechanize#post to store entries with a :order field in addition to the 'name' field that Mechanize::Form::Field#<=> uses to keep custom entries in the proper position.

[ryansch]

I dove deeper into the '#sort' stuff and it works as intended as long as each node is backed by nokogiri. If you build up a form from hashes, the sort order is incorrect.

Edit: Looks like @jasonwbarnett is doing a very similar thing with arrays.

@drbrain I can change the way we're using mechanize in capybara-mechanize to rely more on nokogiri. Is this an issue you want fixed in mechanize itself?

[ryansch]

Another clarification. Jason and I are having the same problem from 2 different entry points. I'm building a form with code similar to @m_form.fields << Mechanize::Form::Field.new({'name' => key.to_s}, value) and then calling @agent.submit on that form. Jason is calling @agent.post which builds a form consisting of fields built from hashes as well. The end result is the same.