chore: generic customized error page

app/controllers/errors_controller.rb

@@ -17,6 +17,13 @@ class ErrorsController < ApplicationController
 
   def not_found = render_error 404
 
+  def show # generic page for others errors
+    @status = params[:status].to_i
+    @error_name = Rack::Utils::HTTP_STATUS_CODES[@status]
+
+    render_error @status
+  end
+
   private
 
   def render_error(status)

app/views/errors/show.en.html.haml

@@ -0,0 +1,19 @@
+%main#content{ role: "main" }
+  .fr-container
+    .fr-my-7w.fr-mt-md-12w.fr-mb-md-10w.fr-grid-row.fr-grid-row--gutters.fr-grid-row--middle.fr-grid-row--center
+      .fr-py-0.fr-col-12.fr-col-md-6
+        %h1= @error_name
+        %p.fr-text--sm.fr-mb-3w Error #{@status}
+        %p.fr-text--lead.fr-mb-3w An error prevents this page from loading.
+
+        - if @error_name.present? # valid error code
+          %p.fr-text--sm.fr-mb-5w
+            = link_to("What does that mean?", "https://developer.mozilla.org/en/docs/Web/HTTP/Status/#{@status}", **external_link_attributes)
+
+        %ul.fr-btns-group.fr-btns-group--inline-md
+          %li
+            = link_to("Homepage", root_path, class: "fr-btn")
+          %li
+            = link_to("Contact us", contact_path, class: "fr-btn fr-btn--secondary")
+
+      = render partial: "artwork"

app/views/errors/show.fr.html.haml

@@ -0,0 +1,19 @@
+%main#content{ role: "main" }
+  .fr-container
+    .fr-my-7w.fr-mt-md-12w.fr-mb-md-10w.fr-grid-row.fr-grid-row--gutters.fr-grid-row--middle.fr-grid-row--center
+      .fr-py-0.fr-col-12.fr-col-md-6
+        %h1= @error_name
+        %p.fr-text--sm.fr-mb-3w Erreur #{@status}
+        %p.fr-text--lead.fr-mb-3w Une erreur empêche le chargement de cette page.
+
+        - if @error_name.present? # valid error code
+          %p.fr-text--sm.fr-mb-5w
+            = link_to("Qu’est-ce que cela veut dire ?", "https://developer.mozilla.org/fr/docs/Web/HTTP/Status/#{@status}", **external_link_attributes)
+
+        %ul.fr-btns-group.fr-btns-group--inline-md
+          %li
+            = link_to("Page d’accueil", root_path, class: "fr-btn")
+          %li
+            = link_to("Contactez-nous", contact_path, class: "fr-btn fr-btn--secondary")
+
+      = render partial: "artwork"

config/routes.rb

@@ -700,6 +700,7 @@ Rails.application.routes.draw do
 
   get '/404', to: 'errors#not_found'
   get '/500', to: 'errors#internal_server_error'
+  get '/:status', to: 'errors#show', constraints: { status: /[4-5][0-5]\d/ }
 
   if Rails.env.test?
     scope 'test/api_geo' do

spec/controllers/errors_controller_spec.rb

@@ -0,0 +1,52 @@
+RSpec.describe ErrorsController, type: :controller do
+  render_views
+
+  describe 'GET #show' do
+    # rspec can't easily manage the exceptions_app for a real route,
+    # just verify the action renders correctly
+    let(:status_code) { 426 }
+    let(:status_message) { 'Upgrade Required' }
+
+    context 'HTML format' do
+      subject do
+        get :show, params: { status: status_code }, format: :html
+      end
+
+      it 'correctly handles and responds with an HTML response' do
+        subject
+        expect(response).to have_http_status(status_code)
+        expect(response.body).to include(status_message)
+      end
+    end
+
+    context 'JSON format' do
+      subject do
+        get :show, params: { status: status_code }, format: :json
+      end
+
+      it 'correctly handles and responds with a JSON response' do
+        subject
+        expect(response).to have_http_status(status_code)
+        json_response = response.parsed_body
+
+        expect(json_response['status']).to eq(status_code)
+        expect(json_response['name']).to eq(status_message)
+      end
+    end
+  end
+
+  shared_examples 'specific action' do
+    subject { get action_name }
+
+    it do
+      is_expected.to have_http_status(status_code)
+    end
+
+    context "404" do
+      let(:status_code) { 404 }
+      let(:action_name) { :not_found }
+
+      it_behaves_like 'specific action'
+    end
+  end
+end