conditionally restart systemd unit files via ansible, two styles

with_handlers.yaml

tasks:
  - name: specify a systemd unit file
    become: true
    copy:
      src: foo.service
      dest: /etc/systemd/system
    notify: restart foo
      
  - name: enable the systemd unit file
    become: true
    systemd:
      name: foo
      enabled: yes
      daemon_reload: yes
      state: started
  
handlers:
  - name: restart foo
    become: true
    systemd:
      name: foo
      daemon_reload: yes
      state: restarted

without_handlers.yaml

tasks:
  - name: specify a systemd unit file
    become: true
    copy:
      src: foo.service
      dest: /etc/systemd/system
    register: foo # record the results of this task
      
  - name: enable the systemd unit file
    become: true
    systemd:
      name: foo
      enabled: yes
      daemon_reload: yes
      state: "{{'restarted' if foo.changed else 'started'}}"