Add register keyword for adding customized parsers and formatters

CHANGELOG.md

@@ -11,6 +11,7 @@
 
 * [#1325](https://github.com/ruby-grape/grape/pull/1325): Params: Fix coerce_with helper with Array types - [@ngonzalez](https://github.com/ngonzalez).
 * [#1326](https://github.com/ruby-grape/grape/pull/1326): Fix wrong behavior for OPTIONS and HEAD requests with catch-all - [@ekampp](https://github.com/ekampp), [@namusyaka](https://github.com/namusyaka).
+* [#1330](https://github.com/ruby-grape/grape/pull/1330): Fix built-in parsers and formatters - [@namusyaka](https://github.com/namusyaka).
 
 0.15.0 (3/8/2016)
 =================

lib/grape/error_formatter.rb

@@ -1,8 +1,11 @@
+require 'grape/util/registrable'
+
 module Grape
   module ErrorFormatter
+    extend Registrable
     class << self
       def builtin_formatters
-        {
+        @builtin_formatters ||= {
           serializable_hash: Grape::ErrorFormatter::Json,
           json: Grape::ErrorFormatter::Json,
           jsonapi: Grape::ErrorFormatter::Json,
@@ -12,7 +15,7 @@ def builtin_formatters
       end
 
       def formatters(options)
-        builtin_formatters.merge(options[:error_formatters] || {})
+        builtin_formatters.merge(default_elements).merge(options[:error_formatters] || {})
       end
 
       def formatter_for(api_format, options = {})

lib/grape/formatter.rb

@@ -1,8 +1,12 @@
+require 'grape/util/registrable'
+
 module Grape
   module Formatter
+    extend Registrable
+
     class << self
       def builtin_formmaters
-        {
+        @builtin_formatters ||= {
           json: Grape::Formatter::Json,
           jsonapi: Grape::Formatter::Json,
           serializable_hash: Grape::Formatter::SerializableHash,
@@ -12,7 +16,7 @@ def builtin_formmaters
       end
 
       def formatters(options)
-        builtin_formmaters.merge(options[:formatters] || {})
+        builtin_formmaters.merge(default_elements).merge(options[:formatters] || {})
       end
 
       def formatter_for(api_format, options = {})

lib/grape/parser.rb

@@ -1,16 +1,20 @@
+require 'grape/util/registrable'
+
 module Grape
   module Parser
+    extend Registrable
+
     class << self
       def builtin_parsers
-        {
+        @builtin_parsers ||= {
           json: Grape::Parser::Json,
           jsonapi: Grape::Parser::Json,
           xml: Grape::Parser::Xml
         }
       end
 
       def parsers(options)
-        builtin_parsers.merge(options[:parsers] || {})
+        builtin_parsers.merge(default_elements).merge(options[:parsers] || {})
       end
 
       def parser_for(api_format, options = {})

lib/grape/util/registrable.rb

@@ -0,0 +1,11 @@
+module Grape
+  module Registrable
+    def default_elements
+      @default_elements ||= {}
+    end
+
+    def register(format, element)
+      default_elements[format] = element unless default_elements[format]
+    end
+  end
+end

spec/grape/middleware/formatter_spec.rb

@@ -292,4 +292,23 @@ def to_xml
       expect(subject.call(env)).to be_a(Grape::ServeFile::SendfileResponse)
     end
   end
+
+  context 'inheritable formatters' do
+    class InvalidFormatter
+      def self.call(_, _)
+        { message: 'invalid' }.to_json
+      end
+    end
+    let(:app) { ->(_env) { [200, {}, ['']] } }
+    before do
+      Grape::Formatter.register :invalid, InvalidFormatter
+      Grape::ContentTypes::CONTENT_TYPES[:invalid] = 'application/x-invalid'
+    end
+
+    it 'returns response by invalid formatter' do
+      env = { 'PATH_INFO' => '/hello.invalid', 'HTTP_ACCEPT' => 'application/x-invalid' }
+      _, _, bodies = *subject.call(env)
+      expect(bodies.body.first).to eq({ message: 'invalid' }.to_json)
+    end
+  end
 end