Can't issue HEAD requests to a GET endpoint

[stephencelis]

I'm not sure if this bug belongs here or upstream with rack-mount (https://github.com/josh/rack-mount), but HTTP spec is pretty clear about responses to HEAD being identical to GET (less the response body):

The metainformation contained in the HTTP headers in response to a HEAD request SHOULD be identical to the information sent in response to a GET request. This method can be used for obtaining metainformation about the entity implied by the request without transferring the entity-body itself. This method is often used for testing hypertext links for validity, accessibility, and recent modification.

—http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.4

Below is a basic diff with a spec that fails (not sure if the response should be be nil or an empty string, though).

diff --git a/spec/grape/api_spec.rb b/spec/grape/api_spec.rb
index 486b4b6..7541a26 100644
--- a/spec/grape/api_spec.rb
+++ b/spec/grape/api_spec.rb
@@ -296,6 +296,15 @@ describe Grape::API do
       last_response.status.should eql 201
       last_response.body.should eql 'Created'
     end
+
+    it 'should allow a HEAD request against a GET method' do
+      subject.get '/example' do
+        verb
+      end
+      head '/example'
+      last_response.status.should eql 200
+      last_response.body.should be_empty
+    end
   end

   describe 'filters' do

A potential fix (without modifying rack-mount) would be this diff:

diff --git a/lib/grape/api.rb b/lib/grape/api.rb
index 152e6a5..acdc61f 100644
--- a/lib/grape/api.rb
+++ b/lib/grape/api.rb
@@ -293,7 +293,7 @@ module Grape
         imbue(:afters, [block])
       end

-      def get(paths = ['/'], options = {}, &block); route('GET', paths, options, &block) end
+      def get(paths = ['/'], options = {}, &block); route(%w(GET HEAD), paths, options, &block) end
       def post(paths = ['/'], options = {}, &block); route('POST', paths, options, &block) end
       def put(paths = ['/'], options = {}, &block); route('PUT', paths, options, &block) end
       def head(paths = ['/'], options = {}, &block); route('HEAD', paths, options, &block) end

This diff doesn't address the issue raised in #189, but we could fix that, as well. This diff also breaks a lot of specs.

Any thoughts on how/where the logic should be implemented? I've pinged @josh to see if he thinks any of it belongs in rack-mount.

[dblock]

Lets close this and let everyone comment on #189 which fixes the issue.

[stephencelis]

Can we reopen this? #189 and #190 are separate issues. #189 fixes the fact that HEAD requests can return a body. #190 brings up the fact that you can't issue a HEAD request to a GET endpoint and get identical responses. E.g.,

# in a grape api
get '/test' do
  'hello world'
end

The GET will return a 200 and the HEAD will return a 404:

127.0.0.1 - - [27/Jun/2012 09:40:49] "GET /test HTTP/1.1" 200 11 0.0089
127.0.0.1 - - [27/Jun/2012 09:40:55] "HEAD /test HTTP/1.1" 404 - 0.0005

This means that issuing curl -I to see the headers of a GET endpoint will not work.

[dblock]

You're right, reopening.

[dblock]

I read the spec and I think you're right. If you want to make a proper pull request that has all specs passing (including your new one), will be happy to merge. Don't forget to update CHANGELOG.

[dblock]

When you add a GET route for a resource, a route for the HEAD method will now also be added automatically. You can disable this with do_not_route_head!, which isn't the most amazing name for a method or option - I am open to changing it if someone can please suggest something better.