Bypass formatting for statuses with no entity-body.

Author: tylerdooling

CHANGELOG.md

@@ -5,6 +5,7 @@
 
 * Your contribution here.
 
+* [#1190](https://github.com/ruby-grape/grape/putt/1190): Bypass formatting for statuses with no entity-body - [@tylerdooling](https://github.com/tylerdooling).
 * [#1188](https://github.com/ruby-grape/grape/putt/1188): Allow parameters with more than one type - [@dslh](https://github.com/dslh).
 * [#1179](https://github.com/ruby-grape/grape/pull/1179): Allow all RFC6838 valid characters in header vendor - [@suan](https://github.com/suan).
 * [#1170](https://github.com/ruby-grape/grape/pull/1170): Allow dashes and periods in header vendor - [@suan](https://github.com/suan).

README.md

@@ -1976,6 +1976,11 @@ Built-in formatters are the following.
 * `:serializable_hash`: use object's `serializable_hash` when available, otherwise fallback to `:json`
 * `:binary`: data will be returned "as is"
 
+Response statuses that indicate no content as defined by [Rack](https://github.com/rack)
+[here](https://github.com/rack/rack/blob/master/lib/rack/utils.rb#L567)
+will bypass serialization and the body entity - though there should be none -
+will not be modified.
+
 ### JSONP
 
 Grape supports JSONP via [Rack::JSONP](https://github.com/rack/rack-contrib), part of the

UPGRADING.md

@@ -15,6 +15,14 @@ Identical endpoints with different versions now work correctly. A regression int
 
 See [#1114](https://github.com/ruby-grape/grape/pull/1114) for more information.
 
+#### Bypasses formatters when status code indicates no content
+
+To be consistent with rack and it's handling of standard responses
+associated with no content, both default and custom formatters will now
+be bypassed when processing responses for status codes defined [by rack](https://github.com/rack/rack/blob/master/lib/rack/utils.rb#L567)
+
+See [#1190](https://github.com/ruby-grape/grape/pull/1190) for more information.
+
 ### Upgrading to >= 0.12.0
 
 #### Changes in middleware

lib/grape/middleware/formatter.rb

@@ -20,6 +20,7 @@ def before
 
       def after
         status, headers, bodies = *@app_response
+        return @app_response if Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.include?(status)
 
         if bodies.is_a?(Grape::Util::FileResponse)
           headers = ensure_content_type(headers)

spec/grape/middleware/formatter_spec.rb

@@ -201,6 +201,18 @@ def to_xml
     end
   end
 
+  context 'no content responses' do
+    let(:no_content_response) { ->(status) { [status, {}, ['']] } }
+
+    Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.each do |status|
+      it "does not modify a #{status} response" do
+        expected_response = no_content_response[status]
+        allow(app).to receive(:call).and_return(expected_response)
+        expect(subject.call({})).to eq(expected_response)
+      end
+    end
+  end
+
   context 'input' do
     %w(POST PATCH PUT DELETE).each do |method|
       ['application/json', 'application/json; charset=utf-8'].each do |content_type|