FIX: only allow one user to be created per invite

app/models/invite_redeemer.rb

@@ -11,7 +11,7 @@ InviteRedeemer = Struct.new(:invite, :username, :name, :password, :user_custom_f
     # If `invite_passthrough_hours` is defined, allow them to re-use the invite link
     # to login again.
     if invite.redeemed_at && invite.redeemed_at >= SiteSetting.invite_passthrough_hours.hours.ago
-      return invited_user
+      return get_existing_user
     end
 
     nil

spec/models/invite_redeemer_spec.rb

@@ -128,5 +128,18 @@ describe InviteRedeemer do
       expect(user.group_users.count).to eq(4)
       expect(user.trust_level).to eq(2)
     end
+
+    it "only allows one user to be created per invite" do
+      SiteSetting.invite_passthrough_hours = 4800
+      user = invite_redeemer.redeem
+      invite.reload
+
+      user.email = "john@example.com"
+      user.save!
+
+      another_invite_redeemer = InviteRedeemer.new(invite, username, name)
+      another_user = another_invite_redeemer.redeem
+      expect(another_user).to eq(nil)
+    end
   end
 end