fix: handle ActionController::UnknownFormat with 406 response

app/controllers/application_controller.rb

@@ -18,6 +18,7 @@ class ApplicationController < ActionController::Base
 
   rescue_from ActionController::RoutingError, with: :render_not_found
   rescue_from ActiveRecord::RecordNotFound, with: :render_not_found
+  rescue_from ActionController::UnknownFormat, with: :render_not_acceptable
 
   rescue_from Pundit::NotAuthorizedError, with: :user_not_authorized
   rescue_from Pundit::AuthorizationNotPerformedError, with: :user_not_authorized
@@ -36,6 +37,13 @@ def render_not_found
     end
   end
 
+  def render_not_acceptable
+    respond_to do |format|
+      format.html { render template: 'errors/not_acceptable', layout: false, status: :not_acceptable }
+      format.all { head :not_acceptable }
+    end
+  end
+
   protected
 
   def current_user

app/views/errors/not_acceptable.html.haml

@@ -0,0 +1,56 @@
+!!!
+%html
+  %head
+    = render partial: 'shared/meta_tags'
+    = favicon_link_tag 'favicon.ico'
+    %title codebar.io - Not acceptable
+    :css
+      body {
+        font-family: Helvetica, arial, sans-serif;
+        font-size: 14px;
+        line-height: 1.6;
+        padding-top: 10px;
+        padding-bottom: 10px;
+        background-color: white;
+        padding: 30px;
+      }
+      h1 {
+        color: #652f93;
+        font-size: 2em;
+      }
+      a {
+        color: #652f93;
+      }
+      a:visited,
+      a:link,
+      a:active {
+        text-decoration: none;
+      }
+      a:hover {
+        text-decoration: underline;
+      }
+      h1,h2,h3,h4,h5,h6 {
+        margin: 20px 0 10px;
+        padding: 0;
+        font-weight: bold;
+        -webkit-font-smoothing: antialiased;
+        cursor: text;
+        position: relative;
+      }
+
+      #main {
+        text-align: center;
+        width: 80%;
+        min-width: 680px;
+        margin: 0 auto;
+      }
+
+  %body
+    #main
+      =link_to root_path do
+        =image_tag 'codebar-girl.gif', height: '200px', id: 'animated-logo'
+      #message
+        %h1 Not acceptable
+        %h2 The requested format is not supported.
+        %h3
+          In the meantime why don't you #{link_to 'join our community on Slack', 'https://slack.codebar.io', target: '_blank'}?

spec/controllers/application_controller_spec.rb

@@ -28,4 +28,45 @@ def index
       end
     end
   end
+
+  describe '#render_not_acceptable' do
+    controller do
+      def index
+        raise ActionController::UnknownFormat
+      end
+    end
+
+    context 'with HTML format' do
+      before do
+        get :index, format: :html
+      end
+
+      it 'renders the not_acceptable template' do
+        expect(response.status).to eq(406)
+        expect(response).not_to be_redirect
+      end
+    end
+
+    context 'with JSON format' do
+      before do
+        get :index, format: :json
+      end
+
+      it 'returns empty 406 response' do
+        expect(response.status).to eq(406)
+        expect(response.body).to be_empty
+      end
+    end
+
+    context 'with XML format' do
+      before do
+        get :index, format: :xml
+      end
+
+      it 'returns empty 406 response' do
+        expect(response.status).to eq(406)
+        expect(response.body).to be_empty
+      end
+    end
+  end
 end