refactor(mailer): more thread safe defaults tweaks

app/mailers/application_mailer.rb

@@ -1,6 +1,6 @@
 class ApplicationMailer < ActionMailer::Base
+  include MailerDefaultsConfigurableConcern
   include MailerDolistConcern
-  include MailerHeadersConfigurableConcern
   include MailerMonitoringConcern
   include BalancedDeliveryConcern
   include PriorityDeliveryConcern

app/mailers/concerns/mailer_defaults_configurable_concern.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+module MailerDefaultsConfigurableConcern
+  extend ActiveSupport::Concern
+
+  class_methods do
+    # Save original defaults before they're modified
+    def save_original_defaults
+      @original_default_from ||= self.default[:from]
+      @original_default_host ||= Rails.application.routes.default_url_options[:host]
+      @original_asset_host ||= asset_host
+    end
+
+    # Resets mailer settings to their original values
+    def reset_original_defaults
+      default from: original_default_from, reply_to: original_default_from
+      default_url_options[:host] = original_default_host
+      Rails.application.routes.default_url_options[:host] = original_default_host
+      self.asset_host = original_asset_host
+    end
+
+    def original_default_from = @original_default_from
+    def original_default_host = @original_default_host
+    def original_asset_host = @original_asset_host
+  end
+
+  included do
+    before_action -> { self.class.save_original_defaults }
+    after_action ->  { self.class.reset_original_defaults }
+
+    def configure_defaults_for_user(user)
+      return if !user.is_a?(User) # not for super-admins
+
+      I18n.locale = user.locale
+
+      if user.preferred_domain_demarches_gouv_fr?
+        set_currents_for_demarches_gouv_fr
+      else
+        set_currents_for_legacy
+      end
+
+      # Define mailer defaults
+      from = derive_from_header
+      self.class.default from: from, reply_to: from
+      self.class.default_url_options[:host] = Current.host
+      Rails.application.routes.default_url_options[:host] = Current.host
+
+      original_uri = URI.parse(self.class.original_asset_host) # in local with have http://, but https:// in production
+      self.class.asset_host = "#{original_uri.scheme}://#{Current.host}"
+    end
+
+    def configure_defaults_for_email(email)
+      user = User.find_by(email: email)
+      configure_defaults_for_user(user)
+    end
+
+    private
+
+    def set_currents_for_demarches_gouv_fr
+      Current.application_name = "demarches.gouv.fr"
+      Current.host = ENV.fetch("APP_HOST")
+      Current.contact_email = "contact@demarches.gouv.fr"
+      Current.no_reply_email = NO_REPLY_EMAIL.sub("demarches-simplifiees.fr", "demarches.gouv.fr") # rubocop:disable DS/ApplicationName
+    end
+
+    def set_currents_for_legacy
+      Current.application_name = APPLICATION_NAME
+      Current.host = ENV["APP_HOST_LEGACY"] || ENV.fetch("APP_HOST") # APP_HOST_LEGACY is optional. Without it, we are in the situation withotu double domains
+      Current.contact_email = CONTACT_EMAIL
+      Current.no_reply_email = NO_REPLY_EMAIL
+    end
+
+    def derive_from_header
+      if self.class.original_default_from.include?(NO_REPLY_EMAIL)
+        Current.no_reply_email
+      else
+        "#{Current.application_name} <#{Current.contact_email}>"
+      end
+    end
+  end
+end

app/mailers/concerns/mailer_headers_configurable_concern.rb

@@ -1,41 +0,0 @@
-module MailerHeadersConfigurableConcern
-  extend ActiveSupport::Concern
-
-  included do
-    def configure_defaults_for_user(user)
-      return if user.nil? || !user.is_a?(User) # not for super-admins
-
-      I18n.locale = user.locale
-
-      if user.preferred_domain_demarches_gouv_fr?
-        Current.application_name = "demarches.gouv.fr"
-        Current.host = ENV.fetch("APP_HOST")
-        Current.contact_email = "contact@demarches.gouv.fr"
-        Current.no_reply_email = NO_REPLY_EMAIL.sub("demarches-simplifiees.fr", "demarches.gouv.fr") # rubocop:disable DS/ApplicationName
-      else
-        Current.application_name = APPLICATION_NAME
-        Current.host = ENV["APP_HOST_LEGACY"] || ENV.fetch("APP_HOST") # _LEGACY is optional, fallbagck to default when unset
-        Current.contact_email = CONTACT_EMAIL
-        Current.no_reply_email = NO_REPLY_EMAIL
-      end
-
-      @@original_default_from ||= self.class.default[:from]
-      from = if @@original_default_from.include?(NO_REPLY_EMAIL)
-        Current.no_reply_email
-      else
-        "#{Current.application_name} <#{Current.contact_email}>"
-      end
-
-      self.class.default from: from, reply_to: from
-      self.class.default_url_options[:host] = Current.host
-      Rails.application.routes.default_url_options[:host] = Current.host # link generated by url helpers in tags substitutions
-      self.class.asset_host = Current.application_base_url
-    end
-
-    def configure_defaults_for_email(email)
-      user = User.find_by(email: email)
-
-      configure_defaults_for_user(user)
-    end
-  end
-end

app/mailers/devise_user_mailer.rb

@@ -3,9 +3,9 @@ class DeviseUserMailer < Devise::Mailer
   helper :application # gives access to all helpers defined within `application_helper`.
   helper MailerHelper
   include Devise::Controllers::UrlHelpers # Optional. eg. `confirmation_url`
+  include MailerDefaultsConfigurableConcern
   include MailerDolistConcern
   include MailerMonitoringConcern
-  include MailerHeadersConfigurableConcern
   include BalancedDeliveryConcern
   include PriorityDeliveryConcern