DEV: Modifier for Chat::Mailer to skip summary email for users (#26011)

plugins/chat/lib/chat/mailer.rb

@@ -6,6 +6,11 @@ module Chat
       return unless SiteSetting.chat_enabled
 
       users_with_unprocessed_unread_mentions.find_each do |user|
+        # Apply modifier to `true` -- this allows other plugins to block the chat summary email send
+        if !DiscoursePluginRegistry.apply_modifier(:chat_mailer_send_summary_to_user, true, user)
+          next
+        end
+
         # user#memberships_with_unread_messages is a nested array that looks like [[membership_id, unread_message_id]]
         # Find the max unread id per membership.
         membership_and_max_unread_mention_ids =

plugins/chat/spec/components/chat/mailer_spec.rb

@@ -235,6 +235,26 @@ describe Chat::Mailer do
       assert_only_queued_once
     end
 
+    context "with chat_mailer_send_summary_to_user modifier" do
+      let(:modifier_block) { Proc.new { |_| false } }
+      it "skips when modifier evaluates to false" do
+        SiteSetting.chat_allowed_groups = Group::AUTO_GROUPS[:everyone]
+
+        plugin_instance = Plugin::Instance.new
+        plugin_instance.register_modifier(:chat_mailer_send_summary_to_user, &modifier_block)
+
+        described_class.send_unread_mentions_summary
+
+        assert_summary_skipped
+      ensure
+        DiscoursePluginRegistry.unregister_modifier(
+          plugin_instance,
+          :chat_mailer_send_summary_to_user,
+          &modifier_block
+        )
+      end
+    end
+
     describe "update the user membership after we send the email" do
       before { Jobs.run_immediately! }