problem with with_items + when in ansible 2.2

[Spike]

Hi,

I found this bug, which is closed, but I believe I'm still seeing the same problem:

Ansible 2.x errors on the task with the `with_items` loop with `when: some_var is defined` condition when it is used in a role, but not in a play

https://github.com/ansible/ansible/issues/14383

In my case I have a very simple task in a role:

    - name: install sw requested for this box

      apt:

        name: "{{item}}"

        state: present

        install_recommends: yes

      with_items: "{{additional_sw}}"

      when: additional_sw is defined

this fails with an error:

fatal: [localhost]: FAILED! => {"failed": true, "msg": "'additional_sw' is undefined"}

which is true, but the point of the when: is exactly to avoid that. To make it even weirder, I tried to move the when: to a block wrapping that task, and still get the same error.

Eventually I defined a default value to an empty list in role/defaults/main.yml:

additional_sw: []

this worked but I'd still prefer to resolve the above problem.

any idea what's going on?

thanks,

Spike

[Kai Stian Olstad]

On 23. des. 2016 20:27, Spike wrote:
> I found this bug, which is closed, but I believe I'm still seeing the same
> problem:
>
> Ansible 2.x errors on the task with the `with_items` loop with `when:
> some_var is defined` condition when it is used in a role, but not in a play
> https://github.com/ansible/ansible/issues/14383
>
> In my case I have a very simple task in a role:
>
> - name: install sw requested for this box
> apt:
> name: "{{item}}"
> state: present
> install_recommends: yes
> with_items: "{{additional_sw}}"
> when: additional_sw is defined
>
> this fails with an error:
>
> fatal: [localhost]: FAILED! => {"failed": true, "msg": "'additional_sw' is
> undefined"}
>

> which is true, but the point of the *when:* is exactly to avoid that. To
> make it even weirder, I tried to move the *when:* to a *block* wrapping

> that task, and still get the same error.

You have the point of when wrong, this is by design.
When is applied to every iteration of elements in with_items.

You can read more about it here
https://docs.ansible.com/ansible/playbooks_conditionals.html#loops-and-conditionals

> Eventually I defined a default value to an empty list in
> role/defaults/main.yml:
>
> additional_sw: []
>
> this worked but I'd still prefer to resolve the above problem.
>
> any idea what's going on?

Just remove the when, an change the with_items to
with_items: "{{ additional_sw | default([]) }}"

This translate to, if additional_sw variable is not defined use a empty
list, the result is that the task will be skipped.


--
Kai Stian Olstad

[Spike]

thanks for the explanation Kai, makes sense, it effectively does the same thing I've done by setting a default value, but indeed I didn't understand how when worked in conjunction with the with_items.

Here's however something else related that's happening and I'm not understanding: why does this happens also if I move the task in a block and apply the when to that?

  - block:

    - name: install sw requested for this box

      apt:

        name: "{{item}}"

        state: present

        install_recommends: yes

      with_items: "{{additional_sw}}"

    when: additional_sw is defined

shouldn't the task only be considered if the block is executed? why in this case i'm still getting the same error? and in fact, I also see the problem elsewhere with an include, which is even stranger:

#tasks/main.yml

  - include: interfaces.yml

    when: server_interfaces is defined

    tags:

      - netwrk

#tasks/interfaces.yml

  - name: generate new interfaces file

    template:

      src: interfaces.j2

      dest: /etc/network/interfaces

      owner: root

      group: adm

      mode: 0640

    notify:

      - restart network

  - name: setup rt_tables

    lineinfile:

      dest: /etc/iproute2/rt_tables

      regexp: "^{{item.id}} "

      line: "{{item.id}}      {{item.tname}}"

    with_items: "{{server_rt_tables}}"

    when: server_rt_tables is defined

If I don't define server_interfaces I would expect the interfaces.yml to be skipped. Is that not correct? Instead what I'm seeing is the "generate new interfaces" task being skipped while the setup rt_tables throws the same error. It seems like the tasks are "interpreted" even tho they are supposed to be skipped, which doesn't make sense to me.

any thoughts?

thanks,

Spike

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[Kai Stian Olstad]

On 23. des. 2016 22:13, Spike wrote:
> thanks for the explanation Kai, makes sense, it effectively does the same
> thing I've done by setting a default value, but indeed I didn't understand
> how when worked in conjunction with the with_items.
>
> Here's however something else related that's happening and I'm not
> understanding: why does this happens also if I move the task in a block and
> apply the when to that?

You should really read the documentation, it's documented.
https://docs.ansible.com/ansible/playbooks_blocks.html


> * - block:*
> * - name: install sw requested for this box*
> * apt:*
> * name: "{{item}}"*
> * state: present*
> * install_recommends: yes*
> * with_items: "{{additional_sw}}"*
> * when: additional_sw is defined*

>
> shouldn't the task only be considered if the block is executed? why in this
> case i'm still getting the same error? and in fact, I also see the problem
> elsewhere with an include, which is even stranger:

All the tasks in a block inherit the when, so it's the same as adding a
when on all the task.


> *#tasks/main.yml*
> * - include: interfaces.yml*
> * when: server_interfaces is defined*
> * tags:*
> * - netwrk*
>
> *#tasks/interfaces.yml*
>
> * - name: generate new interfaces file*
> * template:*
> * src: interfaces.j2*
> * dest: /etc/network/interfaces*
> * owner: root*
> * group: adm*
> * mode: 0640*
> * notify:*
> * - restart network*
>
> * - name: setup rt_tables*
> * lineinfile:*
> * dest: /etc/iproute2/rt_tables*
> * regexp: "^{{item.id <http://item.id>}} "*
> * line: "{{item.id <http://item.id>}} {{item.tname}}"*
> * with_items: "{{server_rt_tables}}"*
> * when: server_rt_tables is defined*

>
> If I don't define server_interfaces I would expect the interfaces.yml to be
> skipped. Is that not correct? Instead what I'm seeing is the "generate new
> interfaces" task being skipped while the setup rt_tables throws the same
> error. It seems like the tasks are "interpreted" even tho they are supposed
> to be skipped, which doesn't make sense to me.

You should read the entire page that I linked to in my previous mail
https://docs.ansible.com/ansible/playbooks_conditionals.html

All the task in the include inherits the when.
So all task is executed with the when applied, it's same as manually
adding when to every single task.


> any thoughts?

When alway get applied to the tasks, not the include or the block.
And the Ansible documentation is pretty good, I do recommend reading it,
you will pick up many useful things :-)

--
Kai Stian Olstad

[Spike]

Kai,

wow, school'ed :). I read the docs way back when I picked up when and blocks for the first time and used them for months without a problem thinking I understood what was going on. So when these issues arose I didn't think of checking again. Obviously I had misunderstood it the first time around. Thank you again for the clarifications and reminders.

Spike 

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[Kai Stian Olstad]

On 24. des. 2016 02:54, Spike wrote:
> wow, school'ed :).

Sorry about that :-)


> I read the docs way back when I picked up *when* and
> *blocks* for the first time and used them for months without a problem

> thinking I understood what was going on. So when these issues arose I
> didn't think of checking again. Obviously I had misunderstood it the first
> time around. Thank you again for the clarifications and reminders.

I forgot that in 2.0 and 2.1 this gave a deprecation warning with a
message that this feature will be removed in future releases and that it
will be a fatal error.
So you're right, it did work until 2.2.

--
Kai Stian Olstad