Bad interaction between URITemplate and Faraday parameter parsing means dropped values from queries including multiple values for a parameter

[ivoanjo]

The uri_template gem, which hyperclient uses to build urls, implements RFC6570, that expands a parameter in the {?foo*} format as ?foo=a&foo=b&foo=c.

Unfortunately, faraday's default argument parser (Faraday::Utils.default_params_encoder) is set to the NestedParamsEncoder which only considers parameters to be arrays if they have [] in the key.

The result is that values for a parameter are dropped in this process:

require 'faraday'
require 'uri_template'

Faraday::Utils.default_params_encoder.decode(
  URITemplate.new('http://example.com/{?foo*}').expand(foo: ['a', 'b']).split('?').last
)
=> {"foo"=>"b"}

And thus the resulting faraday request will be missing some of the values.

The solution is to use faraday's other parameter encoder (the FlatParamsEncoder).

I'm working on a PR to fix this, but wanted to open the issue to have something to reference.