Multipart/Form-Data: rewind files after read

Fixes #708

lib/httparty/request/body.rb

@@ -39,7 +39,7 @@ def generate_multipart
           memo += "\r\n"
           memo += "Content-Type: #{content_type(value)}\r\n" if file?(value)
           memo += "\r\n"
-          memo += file?(value) ? value.read : value.to_s
+          memo += content_body(value)
           memo += "\r\n"
         end
 
@@ -68,6 +68,15 @@ def normalize_query(query)
         end
       end
 
+      def content_body(object)
+        if file?(object)
+          object = (file = object).read
+          file.rewind if file.respond_to?(:rewind)
+        end
+
+        object.to_s
+      end
+
       def content_type(object)
         return object.content_type if object.respond_to?(:content_type)
         mime = MIME::Types.type_for(object.path)

spec/httparty/request/body_spec.rb

@@ -62,6 +62,8 @@
 
         it { is_expected.to eq multipart_params }
 
+        it { expect { subject }.not_to change { file.pos } }
+
         context 'when passing multipart as an option' do
           let(:options) { { force_multipart: true } }
           let(:params) do