Strange behavior of Jinja2 expression for same input vars

[Cos Bug]

Hi All,

I'm using a Jinja2 expression to exclude form one list the elements present in another list but it doesn't work as expected.

Here is an extract from a larger playbook which captures the input and out put before and after 'set_fact' statement:

- debug: var=excluded_ids

- debug: var=instance_ids

- name: Exclude them from instance_ids
  set_fact: instance_ids1="{% for item in instance_ids if item not in excluded_ids %}{{ item }}{% endfor %}"

- debug: var=instance_ids1

and here the strange output of instance_ids1 variable:

TASK: [debug var=excluded_ids] ************************************
ok: [127.0.0.1] => {
    "var": {
        "excluded_ids": [
            "i-bae34407"
        ]
    }
}

TASK: [debug var=instance_ids] ************************************
ok: [127.0.0.1] => {
    "var": {
        "instance_ids": [
            "i-bae34407",
            "i-d2e4436f"
        ]
    }
}

TASK: [Exclude them from instance_ids] ****************************
ok: [127.0.0.1] => {"ansible_facts": {"instance_ids1": "u, ud26f"}}


TASK: [debug var=instance_ids1] ***********************************
ok: [127.0.0.1] => {
    "var": {
        "instance_ids1": "u, ud26f"
    }
}

As you can see I get some rubbish in instance_ids1.

But if I run a separate playbook defined like this:

---
#
- hosts: localhost
  connection: local
  gather_facts: no

  vars:

    instance_ids:
      - "i-bae34407"
      - "i-d2e4436f"

    excluded_ids:
      - "i-bae34407"

  tasks:

    - debug: var=excluded_ids

    - debug: var=instance_ids

    - set_fact: instance_ids1="{% for item in instance_ids if item not in excluded_ids %}{{ item }}{% endfor %}"

    - debug: var=instance_ids1

I get the correct/expected behavior:

TASK: [debug var=excluded_ids] ************************************************
ok: [127.0.0.1] => {
    "var": {
        "excluded_ids": [
            "i-bae34407"
        ]
    }
}

TASK: [debug var=instance_ids] ************************************************
ok: [127.0.0.1] => {
    "var": {
        "instance_ids": [
            "i-bae34407",
            "i-d2e4436f"
        ]
    }
}

TASK: [set_fact instance_ids1="{% for item in instance_ids if item not in excluded_ids %}{{ item }}{% endfor %}"] ***
ok: [127.0.0.1] => {"ansible_facts": {"instance_ids1": "i-d2e4436f"}}

TASK: [debug var=instance_ids1] ***********************************************
ok: [127.0.0.1] => {
    "var": {
        "instance_ids1": "i-d2e4436f"
    }
}

Why Ansible / Jinja2 treats these list variables differently ?

Are they stored internally as different types ?

 

In debug statements in both cases they appear to be similar (at least printing out)  ...

Thanks & Regards,

Constantin

[Aneesh Joseph]

have you tried the difference filter  - http://docs.ansible.com/ansible/playbooks_filters.html

I'm not sure if you can combine a for loop and an if condition like that, I would have used something like this

set_fact: instance_ids1="{{ instance_ids  | difference(excluded_ids) }}"

or

set_fact: instance_ids1="{% for item in instance_ids %}{% if item not in excluded_ids %}{{ item }}{% endif %}{% endfor %}"

On Wednesday, July 6, 2016 at 3:29:59 PM UTC+5:30, Cos Bug wrote:

Hi All,

Enter code here...

[Cos Bug]

Thanks Aneesh,

The first suggestion brings this:

TASK: [Exclude them from instance_ids] ****************************

ok: [127.0.0.1] => {"ansible_facts": {"instance_ids1": "set([u' ', u'd', u'f', u',', u'2', u'u', u'6'])"}}

TASK: [debug var=instance_ids1] ***********************************
ok: [127.0.0.1] => {
    "var": {

        "instance_ids1": "set([u' ', u'd', u'f', u',', u'2', u'u', u'6'])"
    }
}

the second one doesn't work either (already tried before posting this :-) ).

Tested with Ansible version 1.9.4 & 2.2.0

[Aneesh Joseph]

Hey, tried both in 2.2.0 and they work for me

---
#
- hosts: localhost
  connection: local
  gather_facts: no


  vars:


    instance_ids:
      - "i-bae34407"
      - "i-d2e4436f"


    excluded_ids:
      - "i-bae34407"


  tasks:


    - debug: var=excluded_ids


    - debug: var=

instance_ids


    - set_fact: instance_ids1="{% for item in instance_ids %}{% if item not in excluded_ids %}{{ item }}{% endif %}{% endfor %}"


    - debug: var=instance_ids1

Result

 [WARNING]: provided hosts list is empty, only localhost is available




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


TASK [debug] *******************************************************************
ok: [localhost] => {
    "excluded_ids": [
        "i-bae34407"
    ]
}


TASK [debug] *******************************************************************
ok: [localhost] => {
    "instance_ids": [
        "i-bae34407",
        "i-d2e4436f"
    ]
}


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


TASK [debug] *******************************************************************
ok: [localhost] => {
    "instance_ids1": "i-d2e4436f"
}


PLAY RECAP *********************************************************************
localhost                  : ok=4    changed=0    unreachable=0    failed=0

---
#
- hosts: localhost
  connection: local
  gather_facts: no


  vars:


    instance_ids:
      - "i-bae34407"
      - "i-d2e4436f"


    excluded_ids:
      - "i-bae34407"


  tasks:


    - debug: var=excluded_ids


    - debug: var=

instance_ids


    - set_fact: instance_ids1="{{ instance_ids  | difference(excluded_ids) }}"


    - debug: var=instance_ids1

Result

 [WARNING]: provided hosts list is empty, only localhost is available




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


TASK [debug] *******************************************************************
ok: [localhost] => {
    "excluded_ids": [
        "i-bae34407"
    ]
}


TASK [debug] *******************************************************************
ok: [localhost] => {
    "instance_ids": [
        "i-bae34407",
        "i-d2e4436f"
    ]
}


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


TASK [debug] *******************************************************************
ok: [localhost] => {
    "instance_ids1": [
        "i-d2e4436f"
    ]
}


PLAY RECAP *********************************************************************
localhost                  : ok=4    changed=0    unreachable=0    failed=0

[Cos Bug]

Yes, they work both in a test script where both the excluded_ids and  instance_ids  variables are defined manually but not in original playbook in which these variables are registered as outputs from other modules/tasks

despite the debug shows that their contents are the same.