Custom filter plugin - access Ansible variables?

I’m writing a custom filter plugin in Python, to perform some complicated business logic which uses several values which are already known as Ansible variables. This is going to take a filename and return a list of modified versions of that filename, in a specific order, which will then be used with the ansible.builtin.first_found filter.

Is there a way for the Python code to access Ansible variables directly, rather than having to pass parameters to the filter function? These will include playbook_dir, role_path, a few calculated values, and a few “facts” supplied by /etc/ansible/facts.d/ files on the target machines.

I ask because the immediate problem I’m trying to solve needs the values of eight different variables, and I really don’t want to have to pass every single one of those variables to the filter every time I call it.

Filters aren’t really intended to access data they weren’t explicitly passed. While it might technically be possible, it’s easier to use a lookup plugin (which has a Templar instance available to it) for this purpose. A couple of toy examples can be found at 0_test.yml · GitHub and 0_test.yml · GitHub, or you can look at the usage of templating in the ansible.builtin.first_found and ansible.builtin.vars lookups.

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Can you point me to some documentation which explains what a “Templar instance” is, and how to make use of it?

I pointed you to several things that show you how to use it. What questions are you left with after reading through the examples that I provided?

The term “Templar” is not something I’ve ever seen in the context of computers, let alone Ansible.

Again, what is a “Templar instance”?

Your comment above mentioned it in passing, as if I’m supposed to already know what that means. I just asked for clarification - the email notification came in over the weekend, I plan on looking over those examples later today.

You could search for the string templar in the links @flowerysong provided to see it in action. Alternatively look up the definition of that class in ansible-core’s source code (ansible/lib/ansible/template/ at devel · ansible/ansible · GitHub).

I did see it “in action”, I was asking where to find the official documentation about it. The search engines keep directing me to pages about a Nicholas Cage movie, or to the old religious order mentioned in that movie. It’s really weird, like … maybe the movie industry is paying google to send clicks their way or something?

Anyway. After a good night’s sleep, and reading the documentation about “lookup plugins”, it turns out that within the run() function I can use variables.get( 'xxx' , '' ) to retrieve the value of any variable that can be “seen” by the task which executes the plugin. This, plus “use a lookup plugin instead of a filter plugin”, are all I was looking for in the first place.

The only other thing I ran into is that environment happens to be an undocumented “magic” variable that you can’t use … but that’s not on anybody here, unless you’re part of the ansible documentation team.

Thanks for nudging me in the right direction, much appreciated.

The only official documentation is the ansible-core source code.

The “ansible documentation team” is basically the community. So it includes both you and me :slight_smile: