Alternative to templating inside `when` when trying to dynamically form a conditional

Question

I am trying to dynamically create a conditional by declaring the following variable

in_tags: in ansible_run_tags or "all" in ansible_run_tags

and use it in a when condition like so

- include: zsh.yml
  when: '"zsh" {{ in_tags }}'

However Ansible gives the following warning when I do so

[WARNING]: conditional statements should not include jinja2 templating delimiters such as {{ }} or {%
%}. Found: "zsh" {{ in_tags }}

Removing the {{ }} causes this to fail.

fatal: [localhost]: FAILED! => {"msg": "The conditional check '\"zsh\" in_tags' failed. The error was: template error while templating string: expected token 'end of statement block', got 'in_tags'. String: {% if \"zsh\" in_tags %} True {% else %} False {% endif %}\n\nThe error appears to be in '[REDACTED]/playbook/roles/fzf/tasks/zsh.yml': line 1, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: Ensure zsh integration\n  ^ here\n"}

Is there a better way to write this to avoid templating within the conditional statement?

Have you tried `debug` for `in_tags` variable? Is `zsh` in it? — seshadri_c, Nov 17 '20 at 04:06

score 1 · Accepted Answer · answered Nov 17 '20 at 04:10

1

In order to achieve the dynamic evaluation in a when block, a custom test is the correct way to do that

mkdir test_plugins
cat > test_plugins/my_when_test.py<<"PY"
def my_when_test(the_tag, ansible_run_tags):
    return the_tag in ansible_run_tags or "all" in ansible_run_tags

class TestModule(object):
    def tests(self):
        return {
            "my_when_test": my_when_test,
        }
PY

- include: zsh.yml
  when: '"zsh" is my_when_test(ansible_run_tags)'

There does not appear to be a way to reference things in the vars or hostvars from either a filter or a test. Obviously, if you prefer you can invert the order as when: ansible_run_tags is my_when_test("zsh") by swapping the order of the test function's arguments, if you feel that reads nicer (and saves you the need for the outer ' in yaml)

answered Nov 17 '20 at 04:10

mdaniel

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This was super helpful, and I think it might be the closest I can get to what I want to do without having that annoying warning. I really wish there was a way for me to store it as a partial function somewhere like having the test return a lambda, but that doesn't seem to work unsurprisingly. Thanks a ton though! You have a small typo by the way, you defined the test as `my_when_test` but then tried referencing it as `my_when_filter` – Adrian Ordonez Nov 17 '20 at 04:31
@AdrianOrdonez you can edit the answer yourself to correct it. But it looks like it was done before you even commented :) – Zeitounator Nov 17 '20 at 12:53
@Zeitounator Oh, I didn't know that. Thanks for letting me know! =) – Adrian Ordonez Nov 17 '20 at 19:18

Alternative to templating inside `when` when trying to dynamically form a conditional

1 Answers1