Fix ethon typhoeus exception handling

[blaze182]

Hi everyone and thanks for the fabulous gem.

What is the purpose of this pull request?

This PR improves integration with Ethon and Typhoeus libraries. Sniffer is currently interfering with the behaviour of these libs on network errors, and is not parsing urls prepended with http(s):// correctly.

What changes did you make? (overview)

NoMethodError

Sniffer is currently crashing with NoMethodError: undefined method 'each_with_object' for nil:NilClass if Ethon/Typhoeus request fails with any kind of network errors (host not found, timeout, etc.). However, the original behaviour of those libraries is to not raise any exceptions on .perform / .run respectively.

The reason is @response_headers is empty and is returning nil after split:

sniffer/lib/sniffer/adapters/ethon_adapter.rb

Lines 59 to 64 in cdd52e4

	hash_headers = @response_headers
	.split(/\r?\n/)[1..-1]
	.each_with_object({}) do |item, res|
	k, v = item.split(": ")
	res[k] = v
	end

In order to prevent interfering with original libraries' behaviour, I propose another shared spec example which runs unresolved_request twice (hence the method instead of let) with and without Sniffer, and compares the error outcomes.

URL parsing

URI("http://#{url}") should become URI(url.start_with?(%r{https?://}) ? url : "http://#{url}"), otherwise we have a shift in Sniffer's host and query (i.e. host equals "https", query is "//localhost:4567/?author=Matz"). Ethon and Typhoeus support both formats of the urls.

Checklist

• I've added tests for this change
• I've added a Changelog entry
• I've updated a documentation

[composerinteralia]

FWIW I just ran into this while trying to use sniffer (via https://github.com/palkan/isolator/) at GitHub.

[Aubermean]

@aderyabin ⏰