Ability to handle incoming JSON in the body

This allows Grape to work with ActiveResource in
JSON mode. If the body contains JSON, it's
contents will be added to the params hash just
like if they came over the GET query string or as
regular params.

Author: Ted Kulp

lib/grape/middleware/formatter.rb

@@ -15,12 +15,16 @@ class Formatter < Base
         :json => :encode_json,
         :txt => :encode_txt,
       }
+      PARSERS = {
+        :json => :decode_json
+      }
 
       def default_options
         { 
           :default_format => :txt,
           :formatters => {},
-          :content_types => {}
+          :content_types => {},
+          :parsers => {}
         }
       end
 
@@ -31,6 +35,10 @@ def content_types
       def formatters
         FORMATTERS.merge(options[:formatters])
       end
+
+      def parsers
+        PARSERS.merge(options[:parsers])
+      end
 
       def mime_types
         content_types.invert
@@ -44,7 +52,19 @@ def before
         fmt = format_from_extension || format_from_header || options[:default_format]
 
         if content_types.key?(fmt)
-          env['api.format'] = fmt          
+          if !env['rack.input'].nil? and (body = env['rack.input'].read).length != 0
+            parser = parser_for fmt
+            unless parser.nil?
+              begin
+                env['rack.request.form_hash'] = !env['rack.request.form_hash'].nil? ? env['rack.request.form_hash'].merge(parser.call(body)) : parser.call(body)
+                env['rack.request.form_input'] = env['rack.input']
+              rescue
+                throw :error, :status => 400, :message => 'Body content could not be parsed.'
+              end
+            end
+            env['rack.input'].rewind
+          end
+          env['api.format'] = fmt
         else
           throw :error, :status => 406, :message => 'The requested format is not supported.'
         end
@@ -103,6 +123,22 @@ def formatter_for(api_format)
           spec
         end
       end
+
+      def parser_for(api_format)
+        spec = parsers[api_format]
+        case spec
+        when nil
+          nil
+        when Symbol
+          method(spec)
+        else
+          spec
+        end
+      end
+
+      def decode_json(object)
+        MultiJson.decode(object)
+      end
 
       def encode_json(object)
         if object.respond_to? :serializable_hash

spec/grape/middleware/formatter_spec.rb

@@ -123,4 +123,16 @@ def serializable_hash
       body.body.should == ['CUSTOM JSON FORMAT']
     end
   end
+
+  context 'Input' do
+    it 'should parse the body from a POST/PUT and put the contents into rack.request.form_hash' do
+      subject.call({'PATH_INFO' => '/info', 'Accept' => 'application/json', 'rack.input' => StringIO.new('{"is_boolean":true,"string":"thing"}')})
+      subject.env['rack.request.form_hash']['is_boolean'].should be_true
+      subject.env['rack.request.form_hash']['string'].should == 'thing'
+    end
+    it 'should be able to fail gracefully if the body is invalid' do
+      err = catch(:error){ subject.call({'PATH_INFO' => '/info', 'Accept' => 'application/json', 'rack.input' => StringIO.new('{"is_boolean":true,string:"thing"}')}) }
+      err.should == {:status => 400, :message => "Body content could not be parsed."}
+    end
+  end
 end