options.merge: return the same object if the one being merged is empty

lib/httpx/options.rb

@@ -146,8 +146,10 @@ module HTTPX
     end
 
     def merge(other)
-      h1 = to_hash
       h2 = other.to_hash
+      return self if h2.empty?
+
+      h1 = to_hash
 
       merged = h1.merge(h2) do |k, v1, v2|
         case k

lib/httpx/session.rb

@@ -5,7 +5,9 @@ module HTTPX
     include Loggable
     include Chainable
 
-    def initialize(options = {}, &blk)
+    EMPTY_HASH = {}.freeze
+
+    def initialize(options = EMPTY_HASH, &blk)
       @options = self.class.default_options.merge(options)
       @responses = {}
       @persistent = @options.persistent
@@ -36,6 +38,14 @@ module HTTPX
       responses
     end
 
+    def build_request(verb, uri, options = EMPTY_HASH)
+      rklass = @options.request_class
+      request = rklass.new(verb, uri, @options.merge(options).merge(persistent: @persistent))
+      request.on(:response, &method(:on_response).curry[request])
+      request.on(:promise, &method(:on_promise))
+      request
+    end
+
     private
 
     def pool
@@ -122,8 +132,8 @@ module HTTPX
       requests = case args.size
                  when 1
                    reqs = args.first
-                   reqs.map do |verb, uri|
-                     build_request(verb, uri, request_options)
+                   reqs.map do |verb, uri, opts = EMPTY_HASH|
+                     build_request(verb, uri, request_options.merge(opts))
                    end
                  when 2, 3
                    verb, uris = args