Python set objects in Jinja?

[Justin Lloyd]

Maybe I'm missing something obvious, but is it possible to define a Python set object in Jinja2 code? This doesn't work:

{% set files = set(['/tmp/foo', '/tmp/bar']) %}

It fails with the message "Jinja variable 'set' is undefined".

The problem I need to solve is that I need to iterate over the 'files' variable to create new files so it must be a list of unique values. FWIW, in reality I'm generating 'files' from multiple Pillar keys that could contain duplicate values.

[Loren Gordon]

I don't think jinja2 is able to do that. You could write the state in the pure python renderer, though. Or you could iterate over the list to compare whether the item is already in the list. But it's ugly in Jinja, because inside a loop the variables you set are not available outside the loop; to workaround that, you need to use a map and the update() function...

{% set files = [ 'foo', 'foo', 'bar', 'abc', 'bar' ] %}

{% set dummymap = {'files': []} %}

{% for file in files if file not in dummymap.files %}

    {% do dummymap.update({'files': dummymap.files + [file]}) %}

{% endfor %}

mystate:

  cmd.run:

    - name: echo {{ dummymap.files }}

-Loren

[Justin Lloyd]

I worked around it by just wrapping an simple check whether the value is already in the list around the append call, but it's good to know I wasn't missing anything obvious. I also didn't know about the "for ... if ..." syntax, so TIL. Thanks!

Justin

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[Loren Gordon]

Oh, right, append() works on lists. Don't need the map after all because the list contents persist outside the loop. And yeah, the inline if syntax is very handy. It also works with "do... if..." and "set = ... if ...". Even supports an "else" clause.

{% set files = [ 'foo', 'foo', 'bar', 'abc', 'bar' ] %}

{% set fileset = [] %}

{% for file in files if file not in fileset %}

    {% do fileset.append(file) %}

{% endfor %}

Also, fwiw, there is an open issue to support custom filters, which we could use to implement "set" functions...

https://github.com/saltstack/salt/issues/28236

-Loren

[Justin Lloyd]

Yeah, this is much cleaner, ultimately just appending the conditional to the for statement.

{% set plugins = salt.pillar.get('collectd:plugins:default', []) %}
{% for role in grains['roles'] %}
{%   for plugin in salt.pillar.get('collectd:plugins:' + role, []) if plugin not in plugins %}
{%     do plugins.append(plugin) %}
{%   endfor %}
{% endfor %}

Thanks for the tips!

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