Add support for on_data with faraday.

Followed style of #656 for Typhoeus.

lib/vcr/middleware/faraday.rb

@@ -45,9 +45,11 @@ def initialize(app, env)
         end
 
         def handle
-          # Faraday must be exlusive here in case another library hook is being used.
+          # Faraday must be exclusive here in case another library hook is being used.
           # We don't want double recording/double playback.
           VCR.library_hooks.exclusive_hook = :faraday
+          collect_chunks if env.request.stream_response?
+
           super
         ensure
           response = defined?(@vcr_response) ? @vcr_response : nil
@@ -111,6 +113,7 @@ def on_recordable_request
           @has_on_complete_hook = true
           response = app.call(env)
           response.on_complete do
+            restore_body_from_chunks(env.request) if env.request.stream_response?
             @vcr_response = response_for(response)
             VCR.record_http_interaction(VCR::HTTPInteraction.new(vcr_request, @vcr_response))
             invoke_after_request_hook(@vcr_response) if delay_finishing?
@@ -121,6 +124,20 @@ def invoke_after_request_hook(response)
           super
           VCR.library_hooks.exclusive_hook = nil
         end
+
+        def collect_chunks
+          caller_on_data = env.request.on_data
+          chunks = ''
+          env.request.on_data = Proc.new do |chunk, overall_received_bytes|
+            chunks += chunk
+            env.request.instance_variable_set(:@chunked_body, chunks)
+            caller_on_data.call(chunk, overall_received_bytes)
+          end
+        end
+
+        def restore_body_from_chunks(request)
+          env[:body] = request.instance_variable_get(:@chunked_body)
+        end
       end
     end
   end

spec/lib/vcr/library_hooks/faraday_spec.rb

@@ -42,5 +42,34 @@
       VCR::Middleware::Faraday
     ])
   end
+
+  context 'when using on_data callback' do
+    def make_request
+      VCR.use_cassette('no_body') do
+        conn = Faraday.new(:url => "http://localhost:#{VCR::SinatraApp.port}") do |builder|
+          builder.request  :url_encoded
+          builder.response :logger
+          builder.adapter  :net_http
+        end
+        conn.get("localhost_test") do |request|
+          request.options.on_data = Proc.new do |chunk, overall_received_bytes|
+            on_data_capture.push [chunk, overall_received_bytes]
+          end
+        end
+      end
+    end
+
+    let(:on_data_capture) { [] }
+
+    it 'records and replays correctly' do
+      expect(on_data_capture).to receive(:push).with(["Localhost response", 18])
+
+      recorded = make_request
+      played_back = make_request
+
+      expect(recorded.body).to eq('Localhost response')
+      expect(played_back.body).to eq(recorded.body)
+    end
+  end
 end