ansible:已设置检查变量列表的正确方法? [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

但是，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对此抱怨:

But ansible complains about this:

[WARNING]:当语句不应包含jinja2模板分隔符时，例如{{}}或{％％}.找到:{{item}}是 未定义

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

遍历变量名列表并检查是否已设置变量的正确方法是什么?

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

尽管没有显示您指定的错误消息，但是显示了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.

^{该模块甚至都不会执行，因此您可以使用在上面的示例中用debug替换了fail的ー.}

^{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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