UX: Require a confirmation if approving a post in a closed topic

app/models/reviewable_queued_post.rb

@@ -13,9 +13,18 @@ class ReviewableQueuedPost < Reviewable
   def build_actions(actions, guardian, args)
 
     unless approved?
-      actions.add(:approve_post) do |a|
-        a.icon = 'check'
-        a.label = "reviewables.actions.approve_post.title"
+
+      if topic&.closed?
+        actions.add(:approve_post_closed) do |a|
+          a.icon = 'check'
+          a.label = "reviewables.actions.approve_post.title"
+          a.confirm_message = "reviewables.actions.approve_post.confirm_closed"
+        end
+      else
+        actions.add(:approve_post) do |a|
+          a.icon = 'check'
+          a.label = "reviewables.actions.approve_post.title"
+        end
       end
     end
 
@@ -106,6 +115,10 @@ class ReviewableQueuedPost < Reviewable
     end
   end
 
+  def perform_approve_post_closed(performed_by, args)
+    perform_approve_post(performed_by, args)
+  end
+
   def perform_reject_post(performed_by, args)
     # Backwards compatibility, new code should listen for `reviewable_transitioned_to`
     DiscourseEvent.trigger(:rejected_post, self)

config/locales/server.en.yml

@@ -4521,6 +4521,7 @@ en:
         title: "Approve"
       approve_post:
         title: "Approve Post"
+        confirm_closed: "This topic is closed. Would you like to create the post anyway?"
       reject_post:
         title: "Reject Post"
       approve_user: