allow APIs to declare additional content-types

README.markdown

@@ -209,6 +209,16 @@ end
       end
     end
 
+## Content-Types
+
+By default, Grape supports _XML_, _JSON_, _Atom_, _RSS_, and _text_ content-types. Your API can declare additional types to support. Response format is determined by the request's extension or `Accept` header.
+
+```ruby
+class Twitter::API < Grape::API
+  content_type :xls, "application/vnd.ms-excel"
+end
+```
+
 ## Writing Tests
 
 You can test a Grape API with RSpec. Tests make HTTP requests, therefore they

lib/grape/api.rb

@@ -122,6 +122,12 @@ def error_format(new_format = nil)
         new_format ? set(:error_format, new_format.to_sym) : settings[:error_format]
       end
 
+      # Specify additional content-types, e.g.:
+      #   content_type :xls, 'application/vnd.ms-excel'
+      def content_type(key, val)
+        settings.imbue(:content_types, key.to_sym => val)
+      end
+
       # Specify the default status code for errors.
       def default_error_status(new_status = nil)
         new_status ? set(:default_error_status, new_status) : settings[:default_error_status]

lib/grape/endpoint.rb

@@ -248,7 +248,9 @@ def build_middleware
         }
       end
 
-      b.use Grape::Middleware::Formatter, :default_format => settings[:default_format] || :json
+      b.use Grape::Middleware::Formatter,
+        :default_format => settings[:default_format] || :json,
+        :content_types => settings[:content_types]
 
       aggregate_setting(:middleware).each do |m|
         m = m.dup

spec/grape/api_spec.rb

@@ -679,6 +679,17 @@ def hello
     end
   end
 
+  describe ".content_type" do
+    it "sets additional content-type" do
+      subject.content_type :xls, "application/vnd.ms-excel"
+      subject.get(:hello) do
+        "some binary content"
+      end
+      get '/hello.xls'
+      last_response.content_type.should == "application/vnd.ms-excel"
+    end
+  end
+
   describe ".default_error_status" do
     it 'should allow setting default_error_status' do
       subject.rescue_from :all