Monkey

把表达式 当成变量存储 ，only_if 动作 去解析 执行

ansible 中变量 可以 组合

- role: foo
  param1: '{{ foo }}'
  param2: '{{ some_var1 + "/" + some_var2 }}'
  when: ansible_os_family == 'RedHat'

SHA e6406fa5

  vars:
     favcolor: "red"
     ssn: 8675309
     is_favcolor_blue: "'$favcolor' == 'blue'"
#     is_centos: "'$facter_operatingsystem' == 'CentOS'"

  tasks:

     - name: "do this if my favcolor is blue"
       action: shell /bin/false
       only_if: '$is_favcolor_blue'

实现方式

这种神奇的方式，在ansible中是这样实现的

1. 调用double_template 对变量进行两层替换
2. 对替换的结果 执行eval

runner.py v0.0.2 中

def _execute_module(self, conn, tmp, remote_module_path, args, 
    async_jid=None, async_module=None, async_limit=None):
    ''' runs a module that has already been transferred '''

    inject = self.setup_cache.get(conn.host,{})
    conditional = utils.double_template(self.conditional, inject)
    if not eval(conditional):
        return [ utils.smjson(dict(skipped=True)), None, 'skipped' ]

#host file
[staging]
staging.myproject.com nickname=staging vm=0 branch=develop

#playbook
vars:
favcolor: “red”
dog: “fido”
cat: “whiskers”
ssn: 8675309

• name: Upload SSH key.
  copy: src=key dest=/home/.ssh/id_rsa mode=0600
  only_if: “$vm == 0”

• name: “do this if my favcolor is blue, and my dog is named fido”
  action: shell /bin/false
  when_string: $favcolor == ‘blue’ and $dog == ‘fido’

These are the types of when statemnets available

when_set: $variable_name

when_unset: $variable_name

when_str: $x == “test”

when_int: $y > 2

when_float: $z => 2.3