FIX: force enable a user's email_private_messages option when user replies via email (#6478)

* Enable user email PM when posting to group or replying to topic via email

* remove extra line

* Add test and fix snake_case

* Only reenable email_private_messages for PM replies

lib/email/receiver.rb

@@ -621,11 +621,6 @@ module Email
     end
 
     def create_group_post(group, user, body, elided, hidden_reason_id)
-      # ensure user PM emails are enabled (since user is posting via email)
-      if !user.staged && !user.user_option.email_private_messages
-        user.user_option.update!(email_private_messages: true)
-      end
-
       message_ids = Email::Receiver.extract_reply_message_ids(@mail, max_message_id_count: 5)
       post_ids = []
 
@@ -648,6 +643,8 @@ module Email
                      topic: post.topic,
                      skip_validations: true)
       else
+        enable_email_pm_setting(user)
+
         create_topic(user: user,
                      raw: body,
                      elided: elided,
@@ -856,6 +853,7 @@ module Email
     def create_reply(options = {})
       raise TopicNotFoundError if options[:topic].nil? || options[:topic].trashed?
       options[:post] = nil if options[:post]&.trashed?
+      enable_email_pm_setting(options[:user]) if options[:topic].archetype == Archetype.private_message
 
       if post_action_type = post_action_for(options[:raw])
         create_post_action(options[:user], options[:post], post_action_type)
@@ -1073,6 +1071,13 @@ module Email
         end
       end
     end
+
+    def enable_email_pm_setting(user)
+      # ensure user PM emails are enabled (since user is posting via email)
+      if !user.staged && !user.user_option.email_private_messages
+        user.user_option.update!(email_private_messages: true)
+      end
+    end
   end
 
 end

spec/components/email/receiver_spec.rb

@@ -531,6 +531,18 @@ describe Email::Receiver do
 
       expect { process(:reply_user_not_matching_but_known) }.to change { topic.posts.count }
     end
+
+    it "re-enables user's email_private_messages setting when user replies to a private topic" do
+      topic.update_columns(category_id: nil, archetype: Archetype.private_message)
+      topic.allowed_users << user
+      topic.save
+
+      user.user_option.update_columns(email_private_messages: false)
+      expect { process(:reply_user_matching) }.to change { topic.posts.count }
+      user.reload
+      expect(user.user_option.email_private_messages).to eq(true)
+    end
+
   end
 
   context "new message to a group" do
@@ -629,7 +641,7 @@ describe Email::Receiver do
       expect(Post.last.raw).to match(/discourse\.rb/)
     end
 
-    it "enables user's email_private_messages option when user emails group" do
+    it "enables user's email_private_messages setting when user emails new topic to group" do
       user = Fabricate(:user, email: "existing@bar.com")
       user.user_option.update_columns(email_private_messages: false)
       expect { process(:group_existing_user) }.to change(Topic, :count)