lib/pleroma/user.ex

@@ -2193,7 +2193,7 @@ defmodule Pleroma.User do
     if String.contains?(user.nickname, "@") do
       user.nickname
     else
-      %{host: host} = URI.parse(user.ap_id)
+      host = Pleroma.Web.WebFinger.domain()
       user.nickname <> "@" <> host
     end
   end

test/pleroma/user_test.exs

@@ -2495,13 +2495,23 @@ defmodule Pleroma.UserTest do
   end
 
   describe "full_nickname/1" do
-    test "returns fully qualified nickname for local and remote users" do
-      local_user =
-        insert(:user, nickname: "local_user", ap_id: "https://somehost.com/users/local_user")
+    test "returns fully qualified nickname for local users" do
+      local_user = insert(:user, nickname: "local_user")
 
+      assert User.full_nickname(local_user) == "local_user@localhost"
+    end
+
+    test "returns fully qualified nickname for local users when using different domain for webfinger" do
+      clear_config([Pleroma.Web.WebFinger, :domain], "plemora.dev")
+
+      local_user = insert(:user, nickname: "local_user")
+
+      assert User.full_nickname(local_user) == "local_user@plemora.dev"
+    end
+
+    test "returns fully qualified nickname for remote users" do
       remote_user = insert(:user, nickname: "remote@host.com", local: false)
 
-      assert User.full_nickname(local_user) == "local_user@somehost.com"
       assert User.full_nickname(remote_user) == "remote@host.com"
     end