条件set_fact不求值

Question

我希望根据以下评估的结果设置一个变量：({{ found_files.files|length > 0 }})，然而，它似乎没有得到充分的评估。可能的问题是什么？

期望的结果：found_files2: /dev/null

结果：

TASK [debug] ********************************************************************************************************************************************************************************
ok: [localhost] => {
    "found_files2": "{'files': [], 'changed': False, 'msg': '', 'matched': 0, 'examined': 0, 'failed': False} if (False) else '/dev/null'"
}

攻略：

---
- hosts: localhost
  gather_facts: no
  vars:
    backup_dir: /home/user1/projects/ansible/modules/backups/router2
  tasks:

    - name: get files in backups/<router name>/
      delegate_to: localhost
      find:
        paths: "{{ backup_dir }}"
      register: found_files

    - set_fact:
        found_files2: "{{ found_files }} if ({{ found_files.files|length > 0 }}) else '/dev/null'"

    - debug: var=found_files2

Answer 1

正确的语法如下

- set_fact:
    found_files2: "{{ found_files if (found_files.files|length > 0) else '/dev/null' }}"

过滤器三元组给出相同的结果

- set_fact:                                                                                         
    found_files2: "{{ (found_files.files|length > 0)|ternary(found_files, '/dev/null') }}"