Fix Urlencoded for nested Hashes (and Arrays)

lib/http/form_data/urlencoded.rb

@@ -53,13 +53,45 @@ def encoder=(implementation)
         end
 
         # Returns form data encoder implementation.
-        # Default: `URI.encode_www_form`.
+        # Default: custom realization.
         #
         # @see .encoder=
         # @return [#call]
         def encoder
-          @encoder ||= ::URI.method(:encode_www_form)
+          @encoder ||= DefaultEncoder.method(:encode)
         end
+
+        # Default encoder
+        module DefaultEncoder
+          class << self
+            def encode(value, prefix = nil)
+              case value
+              when Hash
+                encode_hash(value, prefix)
+              when Array
+                value.map { |v| encode(v, "#{prefix}[]") }.join("&")
+              when nil then prefix.to_s
+              else
+                raise ArgumentError, "value must be a Hash" if prefix.nil?
+                "#{prefix}=#{escape(value)}"
+              end
+            end
+
+            private
+
+            def encode_hash(hash, prefix)
+              hash.map do |k, v|
+                encode(v, prefix ? "#{prefix}[#{escape(k)}]" : escape(k))
+              end.reject(&:empty?).join("&")
+            end
+
+            def escape(value)
+              URI.encode_www_form_component(value)
+            end
+          end
+        end
+
+        private_constant :DefaultEncoder
       end
 
       # @param [#to_h, Hash] data form data key-value Hash

spec/lib/http/form_data/urlencoded_spec.rb

@@ -29,6 +29,11 @@
       it { is_expected.to eq "foo%5Bbar%5D=%D1%82%D0%B5%D1%81%D1%82" }
     end
 
+    context "with nested hashes" do
+      let(:data) { { "foo" => { "bar" => "test" } } }
+      it { is_expected.to eq "foo[bar]=test" }
+    end
+
     it "rewinds content" do
       content = form_data.read
       expect(form_data.to_s).to eq content
@@ -57,8 +62,14 @@
   end
 
   describe ".encoder=" do
-    before { described_class.encoder = ::JSON.method(:dump) }
-    after  { described_class.encoder = ::URI.method(:encode_www_form) }
+    before do
+      @original_encoder = described_class.encoder
+      described_class.encoder = ::JSON.method(:dump)
+    end
+
+    after do
+      described_class.encoder = @original_encoder
+    end
 
     it "switches form encoder implementation" do
       expect(form_data.to_s).to eq('{"foo[bar]":"test"}')