what are bare variable and templated strings

[tin-ot]

Im trying to use with_community.general.filetree and ansible-lint to standardise it.

I'm getting an error :
https://ansible.readthedocs.io/projects/lint/rules/deprecated-bare-vars/#correct-code
( with_community.general.filetree => with_filetree )

I found out that.

Incorrect :

with_filetree: "foo/"
with_filetree: foo/
with_filetree: 
  - "foo/"
with_filetree: 
  - 'foo/'

Correct :

with_filetree: "{{ 'foo/' }}"
with_filetree: 
  - "{{ 'foo/' }}"

But I do not understand it.

It seems like it's not a bug since ssbarnea

is explaining 'When it is a string, it must be a templated string,'

#1621 (comment)

In my understanding we are comparing the directory tree with a string of text and retrieve all the files and directories within that matching directory.

I do not understand the syntax of curly braces and a 'foo' string inside, neither what it is supposed to avoid the confusion with.

PS: the syntax in the doc is not consistent with the actual behavior ( for lists )
https://ansible.readthedocs.io/projects/lint/rules/deprecated-bare-vars/#correct-code

and there is not linted example in the documentation :
https://docs.ansible.com/ansible/latest/collections/community/general/filetree_lookup.html