Enable handling of multipart/form-data content

[weshatheleopard]

We desperately needed that since our project uses some external websites (that we cannot change) that utilize this kind of forms, and we needed to write tests for those. Since HTTP clients use automatically generated content delimeters, I replace them with constant strings to enable creation of tests that do not change.

[bblimke]

@weshatheleopard thanks for sharing this solution.

I'm not sure if this should be added to WebMock by default. This modifies request body and might be confusing. E.g. VCR gem uses request signatures created by WebMock.

I consider adding that as a configuration though.

[weshatheleopard]

@bblimke As I said, we desperately needed this fixed so this is what I was able to throw together in the limited time frame. I might be able to revisit this issue later and modify the comparison routine to ignore the differences in boundary strings, but it will take much bigger intrusion in the code.

[weshatheleopard]

@bblimke I studied the code some more and I'm afraid I need your expertise here. I am not sure how this can be handled on the VCR level since the external code (such as Mechanize) generates new random boundary with every call, so it is not possible to create one persistent signature; the only way to handle that seems to replace all the changing stuff to static values upon entering Webmock code, which is exactly what I do here.

[bblimke]

@weshatheleopard that's the reason why multipart has not been supported by WebMock.

I think your solution is clever and can work as a WebMock feature enabled with a configuration setting, after some small refactoring and specs coverage.

[kwstannard]

@bblimke Sorry for the format here, but I managed a solution that seems to work with RestClient's implementation. Here are the relevant monkey patches:

require 'webmock/request_signature'
require 'webmock/request_pattern'

WebMock::RequestPattern.define_method(:matches?) do |request_signature|
  content_type = request_signature.headers['Content-Type'] if request_signature.headers
  @method_pattern.matches?(request_signature.method) &&
    @uri_pattern.matches?(request_signature.uri) &&
    (@body_pattern.nil? || @body_pattern.matches?(request_signature.body, content_type || "")) &&
    (@headers_pattern.nil? || @headers_pattern.matches?(request_signature.headers)) &&
    (@with_block.nil? || @with_block.call(request_signature))
end

WebMock::BodyPattern::BODY_FORMATS["multipart/form-data"] = "multipart/form-data"
WebMock::BodyPattern.define_method(:assert_non_multipart_body) do |content_type|
  #noop
end
WebMock::BodyPattern.define_method(:body_as_hash) do |body, content_type|
  ct, boundary = content_type.split(/; boundary=/)
  case body_format(ct)
  when :json then
    WebMock::Util::JSON.parse(body)
  when :xml then
    Crack::XML.parse(body)
  when 'multipart/form-data' then

    body.gsub("\r", "").sub(/--\n\z/, "").split("--"+boundary).reduce({}) do |hash, part|
      next hash unless part.present?
      lines = part.strip.lines

      key = lines.shift.match(/; name="(\w*)"/) {|m| m[1].to_s }
      if part_content_type = lines.shift.match(/\AContent-Type: (\S+)/) {|m| m[1] }
        lines.shift
        value = body_as_hash(lines.join("\n"), part_content_type)
      else
        value = part.lines[2..-1].join("\n").strip
      end

      hash[key] = value
      hash

    end

  else
    WebMock::Util::QueryMapper.query_to_values(body, notation: Config.instance.query_values_notation)
  end
end

[bblimke]

@kwstannard thank you. I will revisit support for multipart and your changes when I find some time