Variable in text not replaced and still with braces

There is a json file (this content is transferring as base64 to playbook):

$ cat json
{
  "name": "some_value",
  "envs": "ENV_TEST=true ENV_TEXT={{additional_variable}}"
}

Convert to b64 format:

$ cat json | base64 | tr -d "\n"
ewogICJuYW1lIjogInNvbWVfdmFsdWUiLAogICJlbnZzIjogIkVOVl9URVNUPXRydWUgRU5WX1RFWFQ9e3thZGRpdGlvbmFsX3ZhcmlhYmxlfX0iCn0K

Extra vars for playbook (additional_variable and json_props):

-e additional_variable=additionaltext -e json_props=ewogICJuYW1lIjogInNvbWVfdmFsdWUiLAogICJlbnZzIjogIkVOVl9URVNUPXRydWUgRU5WX1RFWFQ9e3thZGRpdGlvbmFsX3ZhcmlhYmxlfX0iCn0K

Playbook:

---
- hosts: test
  gather_facts: False
  vars:
    props: "{{ json_props | b64decode | from_json }}"
    prop:
      envs: "{{ props.envs }}"
  tasks:
  - debug:
      msg: "{{ additional_variable }}"

  - debug:
      msg: "{{ prop.envs }}"

Output:

TASK [debug] **********************************************************************
ok: [127.0.0.1] => {
    "msg": "additionaltext"
}

TASK [debug] **********************************************************************
ok: [127.0.0.1] => {
    "msg": "ENV_TEST=true ENV_TEXT={{additional_variable}}"
}

How to set variable additional_variable from extra vars to the prop.envs string?

Any ideas?

I expect that output will be "ENV_TEST=true ENV_TEXT=additionaltext"

Solution

The problem is that the value of the variable props have already been 'templated' in the expression

  props: "{{ json_props|b64decode|from_json }}"

You've already found out that given the extra variables

shell> cat evars.yml
additional_variable: additionaltext
json_props: ewogICJuYW1lIjogInNvbWVfdmFsdWUiLAogICJlbnZzIjogIkVOVl9URVNUPXRydWUgRU5WX1RFWFQ9e3thZGRpdGlvbmFsX3ZhcmlhYmxlfX0iCn0K

The playbook

shell> cat pb.yml
- hosts: localhost

  vars:

    props: "{{ json_props|b64decode|from_json }}"

  tasks:

    - debug:
        var: props

gives

shell> ansible-playbook -e @evars.yml pb.yml

PLAY [localhost] ******************************************************************************

TASK [debug] **********************************************************************************
ok: [localhost] => 
  props:
    envs: ENV_TEST=true ENV_TEXT={{additional_variable}}
    name: some_value

The variable additional_variable was not substituted in the attribute envs and explicit expansion of the attribute doesn't help either. Ansible doesn't provide a tool to 'template' a value of a variable in vars. But, you can create a custom filter on your own

shell> cat plugins/filter/template.py
from jinja2 import Environment, BaseLoader


def template(my_string, my_vars):
    rtemplate = Environment(loader=BaseLoader).from_string(my_string)
    return(rtemplate.render(my_vars))


class FilterModule(object):

    def filters(self):
        return {
            'template': template,
        }

Configure the path to the filter plugins DEFAULT_FILTER_PLUGIN_PATH. For example,

shell> grep filter ansible.cfg 
filter_plugins = $PWD/plugins/filter

and use the filter template. As a second argument of the filter you have to provide a dictionary with the variables the template needs for the substitutions

  prop:
    envs: "{{ props.envs|template(vars) }}"

gives what you want

  prop:
    envs: ENV_TEST=true ENV_TEXT=additionaltext

^{Example of a complete playbook for testing

shell> cat pb.yml
- hosts: localhost

vars:

props: "{{ json_props|b64decode|from_json }}"
prop:
envs: "{{ props.envs|template(vars) }}"

tasks:

- debug:
var: props
- debug:
var: additional_variable
- debug:
var: prop

- set_fact:
envs: "{{ props.envs|template(my_vars) }}"
vars:
my_vars:
additional_variable: "{{ additional_variable }}"
- debug:
var: envs

gives
shell> ansible-playbook -e @evars.yml pb.yml

PLAY [localhost] ******************************************************************************

TASK [debug] **********************************************************************************
ok: [localhost] =>
props:
envs: ENV_TEST=true ENV_TEXT={{additional_variable}}
name: some_value

TASK [debug] **********************************************************************************
ok: [localhost] =>
additional_variable: additionaltext

TASK [debug] **********************************************************************************
ok: [localhost] =>
prop:
envs: ENV_TEST=true ENV_TEXT=additionaltext

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

TASK [debug] **********************************************************************************
ok: [localhost] =>
envs: ENV_TEST=true ENV_TEXT=additionaltext

PLAY RECAP ************************************************************************************
localhost: ok=5 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0

A simpler option is passing the filename instead of the encoded content. For example, given the file

shell> cat /tmp/test.json
{
"name": "some_value",
"envs": "ENV_TEST=true ENV_TEXT={{ additional_variable }}"
}

include the variables from the file into a dictionary by include_vars
shell> cat pb.yml
- hosts: localhost

tasks:

- include_vars:
file: "{{ file_json_props }}"
name: props
- debug:
var: props

This way the expressions are 'templated' (expanded) automatically
shell> ansible-playbook -e additional_variable=additionaltext -e file_json_props=/tmp/test.json pb.yml

PLAY [localhost] ******************************************************************************

TASK [debug] **********************************************************************************
ok: [localhost] =>
additional_variable: additionaltext

TASK [include_vars] ***************************************************************************
ok: [localhost]

TASK [debug] **********************************************************************************
ok: [localhost] =>
props:
envs: ENV_TEST=true ENV_TEXT=additionaltext
name: some_value

PLAY RECAP ************************************************************************************
localhost: ok=3 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0}