FIX: `max topic invitations per day` should apply on PM invites as well

FIX: do not apply `max topic invitations per day` on email invites

app/models/topic.rb

@@ -804,6 +804,7 @@ SQL
     end
 
     if target_user && private_message? && topic_allowed_users.create!(user_id: target_user.id)
+      rate_limit_topic_invitation(invited_by)
       add_small_action(invited_by, "invited_user", target_user.username)
 
       create_invite_notification!(
@@ -814,9 +815,9 @@ SQL
 
       true
     elsif username_or_email =~ /^.+@.+$/ && guardian.can_invite_via_email?(self)
-      rate_limit_topic_invitation(invited_by)
 
       if target_user
+        rate_limit_topic_invitation(invited_by)
         Invite.extend_permissions(self, target_user, invited_by)
 
         create_invite_notification!(

spec/models/topic_spec.rb

@@ -471,7 +471,7 @@ describe Topic do
 
     context 'rate limits' do
       before do
-        SiteSetting.max_topic_invitations_per_day = 2
+        SiteSetting.max_topic_invitations_per_day = 1
         RateLimiter.enable
       end
 
@@ -481,7 +481,6 @@ describe Topic do
       end
 
       it "rate limits topic invitations" do
-
         start = Time.now.tomorrow.beginning_of_day
         freeze_time(start)
 
@@ -489,10 +488,23 @@ describe Topic do
         topic = Fabricate(:topic, user: trust_level_2)
 
         topic.invite(topic.user, user.username)
-        topic.invite(topic.user, "walter@white.com")
 
         expect {
-          topic.invite(topic.user, "user@example.com")
+          topic.invite(topic.user, another_user.username)
+        }.to raise_error(RateLimiter::LimitExceeded)
+      end
+
+      it "rate limits PM invitations" do
+        start = Time.now.tomorrow.beginning_of_day
+        freeze_time(start)
+
+        trust_level_2 = Fabricate(:user, trust_level: 2)
+        topic = Fabricate(:private_message_topic, user: trust_level_2)
+
+        topic.invite(topic.user, user.username)
+
+        expect {
+          topic.invite(topic.user, another_user.username)
         }.to raise_error(RateLimiter::LimitExceeded)
       end
     end