add Content-Type header to the 405 response

CHANGELOG.markdown

@@ -17,6 +17,7 @@ Next Release
 * [#190](https://github.com/intridea/grape/issues/190): When you add a `GET` route for a resource, a route for the `HEAD` method will also be added automatically. You can disable this behavior with `do_not_route_head!` - [@dblock](http://github.com/dblock).
 * Added `do_not_route_options!`, which disables the automatic creation of the `OPTIONS` route - [@dblock](http://github.com/dblock).
 * [#335](https://github.com/intridea/grape/pull/335): Fix: request body parameters from a `PATCH` request not available in `params` - [@FreakenK](http://github.com/FreakenK).
+* [#343](https://github.com/intridea/grape/pull/343): Fix: returning 405 with no Content-Type caused Rack to throw Rack::Lint::LintError - [@gustavosaume](https://github.com/gustavosaume) & [@wyattisimo](https://github.com/wyattisimo).
 * Your contribution here.
 
 0.2.6 (01/11/2013)

lib/grape/api.rb

@@ -492,7 +492,7 @@ def add_head_not_allowed_methods
         not_allowed_methods = %w(GET PUT POST DELETE PATCH HEAD) - methods
         not_allowed_methods << "OPTIONS" if self.class.settings[:do_not_route_options]
         not_allowed_methods.each do |bad_method|
-          @route_set.add_route( proc { [405, { 'Allow' => allow_header }, []]}, {
+          @route_set.add_route( proc { [405, { 'Allow' => allow_header, 'Content-Type' => 'text/plain' }, []]}, {
             :path_info      => path_info,
             :request_method => bad_method
           })

spec/grape/api_spec.rb

@@ -395,6 +395,17 @@ def subject.enable_root_route!
       last_response.headers['Allow'].should eql 'OPTIONS, GET, POST, HEAD'
     end
 
+    specify '405 responses includes an Content-Type header' do
+      subject.get 'example' do
+        "example"
+      end
+      subject.post 'example' do
+        "example"
+      end
+      put '/example'
+      last_response.headers['Content-Type'].should eql 'text/plain'
+    end
+
     it 'adds an OPTIONS route that returns a 204 and an Allow header' do
       subject.get 'example' do
         "example"