chore: custom dynamic & static 500 pages

app/controllers/errors_controller.rb

@@ -3,7 +3,40 @@
 class ErrorsController < ApplicationController
   def nav_bar_profile = try_nav_bar_profile_from_referrer
 
-  def not_found
-    render(status: 404)
+  rescue_from Exception do
+    # catch any error, except errors triggered by middlewares outside controller (like warden middleware)
+    render file: Rails.public_path.join('500.html'), layout: false, status: :internal_server_error
+  end
+
+  def internal_server_error
+    # This dynamic template is rendered when a "normal" error occurs, (ie. a bug which is 99.99% of errors.)
+    # However if this action fails (error in the view or in a middlewares)
+    # the exceptions are rescued and a basic 100% static html file is rendererd instead.
+    render_error 500
+  end
+
+  def not_found = render_error 404
+
+  private
+
+  def render_error(status)
+    respond_to do |format|
+      format.html { render status: }
+      format.json { render status:, json: { status:, name: Rack::Utils::HTTP_STATUS_CODES[status] } }
+    end
+  end
+
+  # Intercept errors in before_action when fetching user or roles
+  # when db is unreachable so we can still display a nice 500 static page
+  def current_user
+    super
+  rescue
+    nil
+  end
+
+  def current_user_roles
+    super
+  rescue
+    nil
   end
 end

app/views/errors/internal_server_error.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 Unexpected Error
+        %p.fr-text--sm.fr-mb-3w Error 500
+        %p.fr-text--lead.fr-mb-3w
+          Sorry, an error has occurred. Our teams have been notified
+          to resolve the issue as quickly as possible.
+        %p.fr-text--sm.fr-mb-5w
+          Try refreshing the page or try again a little later.
+          %br
+          If you need immediate assistance, please contact us.
+
+        %ul.fr-btns-group.fr-btns-group--inline-md
+          %li
+            = link_to("Contact Us", contact_path, class: "fr-btn fr-btn--secondary")
+
+      = render partial: "artwork"

app/views/errors/internal_server_error.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 Erreur inattendue
+        %p.fr-text--sm.fr-mb-3w Erreur 500
+        %p.fr-text--lead.fr-mb-3w
+          Désolé, une erreur est survenue. Nos équipes ont été averties
+          pour résoudre le problème le plus rapidement possible.
+        %p.fr-text--sm.fr-mb-5w
+          Essayez de rafraîchir la page ou réessayez un peu plus tard.
+          %br
+          Si le problème persiste, merci de nous contacter.
+
+        %ul.fr-btns-group.fr-btns-group--inline-md
+          %li
+            = link_to("Contactez-nous", contact_path, class: "fr-btn fr-btn--secondary")
+
+      = render partial: "artwork"

config/routes.rb

@@ -699,6 +699,7 @@ Rails.application.routes.draw do
   resources :release_notes, only: [:index]
 
   get '/404', to: 'errors#not_found'
+  get '/500', to: 'errors#internal_server_error'
 
   if Rails.env.test?
     scope 'test/api_geo' do

spec/support/without_detailed_exceptions.rb

@@ -0,0 +1,18 @@
+module WithoutDetailedExceptions
+  RSpec.configure do |config|
+    config.include self, type: :system
+  end
+
+  # Snippet from https://github.com/rspec/rspec-rails/issues/2024
+  def without_detailed_exceptions
+    env_config = Rails.application.env_config
+    original_show_exceptions = env_config['action_dispatch.show_exceptions']
+    original_show_detailed_exceptions = env_config['action_dispatch.show_detailed_exceptions']
+    env_config['action_dispatch.show_exceptions'] = true
+    env_config['action_dispatch.show_detailed_exceptions'] = false
+    yield
+  ensure
+    env_config['action_dispatch.show_exceptions'] = original_show_exceptions
+    env_config['action_dispatch.show_detailed_exceptions'] = original_show_detailed_exceptions
+  end
+end

spec/system/errors_spec.rb

@@ -0,0 +1,29 @@
+describe 'Errors handling', js: false do
+  let(:procedure) { create(:procedure) }
+
+  scenario 'bug renders dynamic 500 page' do
+    procedure.revisions.destroy_all # break procedure
+
+    without_detailed_exceptions do
+      visit commencer_path(path: procedure.path)
+    end
+
+    expect(page).to have_http_status(:internal_server_error)
+    expect(page).to have_content('une erreur est survenue')
+    expect(page).to have_content('Se connecter')
+    expect(page).to have_link('Contactez-nous')
+  end
+
+  scenario 'fatal error fallback to static 500 page' do
+    without_detailed_exceptions do
+      Rails.application.env_config["action_dispatch.cookies"] = "will fail"
+      visit commencer_path(path: procedure.path)
+    ensure
+      Rails.application.env_config.delete("action_dispatch.cookies")
+    end
+
+    expect(page).to have_content('une erreur est survenue')
+    expect(page).not_to have_content('Se connecter')
+    expect(page).to have_link('Contactez-nous')
+  end
+end