如何使用表达式设置结构化变量

Question

Ansible中有没有办法将变量设置为从表达式构造的某个结构化值（例如列表或字典）？

例如，我有这些变量：

all_flavours: ["vanilla", "chocolate", "strawberry", "banana"]
flavours_to_keep: ["chocolate", "banana"]

我想评估表达式all_flavours | difference(flavours_to_keep)并将结果集合（列表或确实设置）存储在变量flavours_to_drop中，这样对于这些值，就好像我已定义：

flavours_to_drop: ["vanilla", "strawberry"]

但是，我找不到这样做的语法。以下是我的尝试：

尝试1

flavours_to_drop: all_flavours | difference(flavours_to_keep)

这只是解释为一个字符串：

flavours_to_drop: "all_flavours | difference(flavours_to_keep)"

尝试2

flavours_to_drop: {{ all_flavours | difference(flavours_to_keep) }}

这是一个错误，因为YAML将“{”解释为字典。

尝试3

flavours_to_drop: "{{ all_flavours | difference(flavours_to_keep) }}"

这正确地设置了差异，但随后将其转换为字符串，所以我最终得到：

flavours_to_drop: "set([\"vanilla\", \"strawberry\"])"

如何评估表达式，但是将结构化对象直接存储回变量而不是将其转换为字符串？

我应该补充说我正在使用Ansible版本1.6.2。这种行为是否在Ansible版本之间发生了变化？

Answer 1

格式化等可能有点棘手。您需要引用过滤器以便正确解析它。您可以将其作为var或set_fact来执行。你想要这样的东西：

vars:
  all_flavours: ["vanilla", "chocolate", "strawberry", "banana"]
  flavours_to_keep: ["chocolate", "banana"]
  flavours_to_drop_1: "{{ all_flavours | difference(flavours_to_keep) }}"

tasks:
  - debug: var=all_flavours

  - debug: var=flavours_to_keep

  - set_fact:
      flavours_to_drop_2: "{{ all_flavours | difference(flavours_to_keep) }}"

  - debug: var=flavours_to_drop_1

  - debug: var=flavours_to_drop_2

以上结果是：

TASK: [debug var=all_flavours]     ************************************************
ok: [localhost] => {
    "all_flavours": [
        "vanilla",
        "chocolate",
        "strawberry",
        "banana"
    ]
}

TASK: [debug var=flavours_to_keep] ********************************************
ok: [localhost] => {
    "flavours_to_keep": [
        "chocolate",
        "banana"
    ]
}

TASK: [set_fact ] *************************************************************
ok: [localhost]

TASK: [debug var=flavours_to_drop_1] ********************************************
ok: [localhost] => {
    "flavours_to_drop_1": [
        "vanilla",
        "strawberry"
    ]
}

TASK: [debug var=flavours_to_drop_2] ********************************************
ok: [localhost] => {
    "flavours_to_drop_2": [
        "vanilla",
        "strawberry"
    ]
}