ansible:检查变量列表的正确方法是否已设置? [英] ansible: correct way to check a list of variables has been set?

问题描述

我正在尝试在 Ansible 2.5 中使用 when: item is undefined 来检查是否已设置变量列表，如下所示:

I'm trying to use when: item is undefined in Ansible 2.5 to check if a list of variables have been set, as below:

- hosts: all
  tasks:
    - name: validate some variables
      fail:
        msg: "Required variable {{item}} has not been provided"
      when: item is undefined
      loop:
        - v1
        - v2

然而，无论是否提供 v1 或 v2，这都不会失败.

However, this never fails regardless of whether v1 or v2 are provided.

切换 when 以使用 jinja2 模板工作:

Switching the when to use jinja2 templating works:

when: "{{item}} is undefined"

但是 ansible 抱怨这个:

But ansible complains about this:

[警告]:when 语句不应包含 jinja2 模板分隔符，例如 {{ }} 或 {% %}.发现:{{item}} 是未定义

[WARNING]: when statements should not include jinja2 templating delimiters such as {{ }} or {% %}. Found: {{item}} is undefined

循环遍历变量名称列表并检查它们是否已设置的正确方法是什么?

What is the correct way loop through a list of variable names and checked they have been set?

推荐答案

使用 vars 结构:

- name: validate some variables
  fail:
    msg: "Required variable {{item}} has not been provided"
  when: vars[item] is undefined
  loop:
    - v1
    - v2

或者，在 Ansible 2.5 中，使用新的 vars 查找插件:

Or, in Ansible 2.5, with the new vars lookup plugin:

- name: validate some variables
  debug:
  when: lookup('vars', item) is undefined
  loop:
    - v1
    - v2

虽然不是您指定的错误消息，而是查找插件的默认错误消息.

Although not with the error message you specified, but a default error message for a lookup plugin.

^{模块甚至不会被执行，所以你可以使用任何我在上面的例子中用 debug 替换 fail 的任何东西.}

^{The module won't even be executed, so you can use whatever ー I replaced fail with debug in the example above.}

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