Configurable JSON encoders and decoders

docs/middleware/included/json.md

@@ -21,6 +21,26 @@ conn.post('/', { a: 1, b: 2 })
 # Body: {"a":1,"b":2}
 ```
 
+### Using custom JSON encoders
+
+By default, middleware utilizes Ruby's `json` to generate JSON strings.
+
+Other encoders can be used by specifying `encoder` option for the middleware:
+* a module/class which implements `encode`
+* a module/class-method pair to be used 
+
+```ruby
+require 'oj'
+
+Faraday.new(...) do |f|
+  f.request :json, encoder: Oj
+end
+
+Faraday.new(...) do |f|
+  f.request :json, encoder: [Oj, :encode]
+end
+```
+
 ## JSON Responses
 
 The `JSON` response middleware parses response body into a hash of key/value pairs.
@@ -39,3 +59,23 @@ end
 conn.get('json').body
 # => {"slideshow"=>{"author"=>"Yours Truly", "date"=>"date of publication", "slides"=>[{"title"=>"Wake up to WonderWidgets!", "type"=>"all"}, {"items"=>["Why <em>WonderWidgets</em> are great", "Who <em>buys</em> WonderWidgets"], "title"=>"Overview", "type"=>"all"}], "title"=>"Sample Slide Show"}}
 ```
+
+### Using custom JSON decoders
+
+By default, middleware utilizes Ruby's `json` to parse JSON strings.
+
+Other decoders can be used by specifying `decoder` parser option for the middleware:
+* a module/class which implements `decode`
+* a module/class-method pair to be used 
+
+```ruby
+require 'oj'
+
+Faraday.new(...) do |f|
+  f.response :json, parser_options: { decoder: Oj }
+end
+
+Faraday.new(...) do |f|
+  f.response :json, parser_options: { decoder: [Oj, :encode] }
+end
+```

lib/faraday/options.rb

@@ -30,15 +30,15 @@ def update(obj)
           new_value = value
         end
 
-        send("#{key}=", new_value) unless new_value.nil?
+        send(:"#{key}=", new_value) unless new_value.nil?
       end
       self
     end
 
     # Public
     def delete(key)
       value = send(key)
-      send("#{key}=", nil)
+      send(:"#{key}=", nil)
       value
     end
 
@@ -57,7 +57,7 @@ def merge!(other)
                     else
                       other_value
                     end
-        send("#{key}=", new_value) unless new_value.nil?
+        send(:"#{key}=", new_value) unless new_value.nil?
       end
       self
     end

lib/faraday/request/json.rb

@@ -24,7 +24,13 @@ def on_request(env)
       private
 
       def encode(data)
-        ::JSON.generate(data)
+        if options[:encoder].is_a?(Array) && options[:encoder].size >= 2
+          options[:encoder][0].public_send(options[:encoder][1], data)
+        elsif options[:encoder].respond_to?(:encode)
+          options[:encoder].encode(data)
+        else
+          ::JSON.generate data
+        end
       end
 
       def match_content_type(env)

lib/faraday/response/json.rb

@@ -27,7 +27,22 @@ def process_response(env)
       end
 
       def parse(body)
-        ::JSON.parse(body, @parser_options || {}) unless body.strip.empty?
+        return if body.strip.empty?
+
+        parser_options = @parser_options.dup || {}
+
+        decoder, method_name =
+          if parser_options[:decoder].is_a?(Array) && parser_options[:decoder].size >= 2
+            parser_options[:decoder].slice(0, 2)
+          elsif parser_options[:decoder].respond_to?(:decode)
+            [parser_options[:decoder], :decode]
+          else
+            [::JSON, :parse]
+          end
+
+        parser_options.delete(:decoder)
+
+        decoder.public_send(method_name, body, parser_options)
       end
 
       def parse_response?(env)

spec/faraday/request/json_spec.rb

@@ -132,4 +132,68 @@ def result_type
       expect(result_type).to eq('application/xml; charset=utf-8')
     end
   end
+
+  context 'with encoder' do
+    let(:encoder) do
+      double('Encoder').tap do |e|
+        allow(e).to receive(:encode) { |s, opts| JSON.generate(s, opts) }
+      end
+    end
+
+    let(:result) { process(a: 1) }
+
+    context 'when encoder is passed as object' do
+      let(:middleware) { described_class.new(->(env) { Faraday::Response.new(env) }, { encoder: encoder }) }
+
+      it 'calls specified JSON encoder' do
+        expect(encoder).to receive(:encode).with({ a: 1 })
+
+        result
+      end
+
+      it 'encodes body' do
+        expect(result_body).to eq('{"a":1}')
+      end
+
+      it 'adds content type' do
+        expect(result_type).to eq('application/json')
+      end
+    end
+
+    context 'when encoder is passed as an object-method pair' do
+      let(:middleware) { described_class.new(->(env) { Faraday::Response.new(env) }, { encoder: [encoder, :encode] }) }
+
+      it 'calls specified JSON encoder' do
+        expect(encoder).to receive(:encode).with({ a: 1 })
+
+        result
+      end
+
+      it 'encodes body' do
+        expect(result_body).to eq('{"a":1}')
+      end
+
+      it 'adds content type' do
+        expect(result_type).to eq('application/json')
+      end
+    end
+
+    context 'when encoder is not passed' do
+      let(:middleware) { described_class.new(->(env) { Faraday::Response.new(env) }) }
+
+      it 'calls JSON.generate' do
+        expect(JSON).to receive(:generate).with({ a: 1 })
+
+        result
+      end
+
+      it 'encodes body' do
+        expect(result_body).to eq('{"a":1}')
+      end
+
+      it 'adds content type' do
+        expect(result_type).to eq('application/json')
+      end
+    end
+  end
 end

spec/faraday/response/json_spec.rb

@@ -114,4 +114,76 @@ def process(body, content_type = 'application/json', options = {})
       expect(response.body).to eq(result)
     end
   end
+
+  context 'with decoder' do
+    let(:decoder) do
+      double('Decoder').tap do |e|
+        allow(e).to receive(:decode) { |s, opts| JSON.parse(s, opts) }
+      end
+    end
+
+    let(:body) { '{"a": 1}' }
+    let(:result) { { a: 1 } }
+
+    context 'when decoder is passed as object' do
+      let(:options) do
+        {
+          parser_options: {
+            decoder: decoder,
+            option: :option_value,
+            symbolize_names: true
+          }
+        }
+      end
+
+      it 'passes relevant options to specified decoder\'s decode method' do
+        expect(decoder).to receive(:decode)
+          .with(body, { option: :option_value, symbolize_names: true })
+          .and_return(result)
+
+        response = process(body)
+        expect(response.body).to eq(result)
+      end
+    end
+
+    context 'when decoder is passed as an object-method pair' do
+      let(:options) do
+        {
+          parser_options: {
+            decoder: [decoder, :decode],
+            option: :option_value,
+            symbolize_names: true
+          }
+        }
+      end
+
+      it 'passes relevant options to specified decoder\'s method' do
+        expect(decoder).to receive(:decode)
+          .with(body, { option: :option_value, symbolize_names: true })
+          .and_return(result)
+
+        response = process(body)
+        expect(response.body).to eq(result)
+      end
+    end
+
+    context 'when decoder is not passed' do
+      let(:options) do
+        {
+          parser_options: {
+            symbolize_names: true
+          }
+        }
+      end
+
+      it 'passes relevant options to JSON parse' do
+        expect(JSON).to receive(:parse)
+          .with(body, { symbolize_names: true })
+          .and_return(result)
+
+        response = process(body)
+        expect(response.body).to eq(result)
+      end
+    end
+  end
 end