How to set Ansible fact over condition

sample.yml

- name: "Retrieve user's home path if not set"
  sudo: yes
  sudo_user: "{{ user }}"
  shell: "echo $HOME"
  register: _user_homedir
  when: user_home == ""

- name: Set home path to be used for configuration
  set_fact:
    user_homedir: "{{ _user_homedir.stdout if user_home == '' else user_home }}"