FIX: UX improvements for system messages when PMs are disabled

app/assets/javascripts/discourse/components/topic-footer-buttons.js.es6

@@ -6,6 +6,16 @@ export default Ember.Component.extend({
   // Allow us to extend it
   layoutName: 'components/topic-footer-buttons',
 
+  @computed('topic.isPrivateMessage')
+  canArchive(isPM) {
+    return this.siteSettings.enable_private_messages && isPM;
+  },
+
+  @computed('topic.isPrivateMessage')
+  showNotificationsButton(isPM) {
+    return (!isPM) || this.siteSettings.enable_private_messages;
+  },
+
   @computed('topic.details.can_invite_to')
   canInviteTo(result) {
     return !this.site.mobileView && result;

app/assets/javascripts/discourse/templates/components/topic-footer-buttons.hbs

@@ -50,8 +50,8 @@
                disabled=inviteDisabled}}
   {{/if}}
 
-  {{#if topic.isPrivateMessage}}
+  {{#if canArchive}}
-    {{d-button class="standard"
+    {{d-button class="standard archive-topic"
                title=archiveTitle
                label=archiveLabel
                icon=archiveIcon
@@ -79,7 +79,9 @@
   {{pinned-button pinned=topic.pinned topic=topic}}
 </div>
 
-{{topic-notifications-button notificationLevel=topic.details.notification_level topic=topic}}
+{{#if showNotificationsButton}}
+  {{topic-notifications-button notificationLevel=topic.details.notification_level topic=topic}}
+{{/if}}
 
 {{plugin-outlet name="after-topic-footer-buttons"
                 args=(hash topic=topic)

config/locales/server.en.yml

@@ -1034,6 +1034,7 @@ en:
     summary_max_results: "Maximum posts returned by 'Summary This Topic'"
 
     enable_private_messages: "Allow trust level 1 (configurable via min trust level to send messages) users to create messages and reply to messages. Note that staff can always send messages no matter what."
+    enable_system_message_replies: "Allows users to reply to system messages, even if private messages are disabled"
     enable_private_email_messages: "Allow trust level 4 (configurable via min trust level to send messages) users to send private email messages. Note that staff can always send messages no matter what."
 
     enable_long_polling: "Message bus used for notification can use long polling"

config/site_settings.yml

@@ -507,6 +507,8 @@ posting:
   enable_private_messages:
     default: true
     client: true
+  enable_system_message_replies:
+    default: true
   enable_private_email_messages:
     default: false
     client: true

lib/guardian/post_guardian.rb

@@ -80,6 +80,9 @@ module PostGuardian
 
   # Creating Method
   def can_create_post?(parent)
+
+    return false if !SiteSetting.enable_system_message_replies? && parent.try(:subtype) == "system_message"
+
     (!SpamRule::AutoSilence.silence?(@user) || (!!parent.try(:private_message?) && parent.allowed_users.include?(@user))) && (
       !parent ||
       !parent.category ||

spec/components/guardian_spec.rb

@@ -857,6 +857,25 @@ describe Guardian do
         end
       end
 
+      context "system message" do
+        let(:private_message) {
+          Fabricate(
+            :topic,
+            archetype: Archetype.private_message,
+            subtype: 'system_message',
+            category_id: nil
+          )
+        }
+
+        before { user.save! }
+        it "allows the user to reply to system messages" do
+          expect(Guardian.new(user).can_create_post?(private_message)).to eq(true)
+          SiteSetting.enable_system_message_replies = false
+          expect(Guardian.new(user).can_create_post?(private_message)).to eq(false)
+        end
+
+      end
+
       context "private message" do
         let(:private_message) { Fabricate(:topic, archetype: Archetype.private_message, category_id: nil) }