Let's say you have a list of dicts, e.g.,

unison_jobs:
  - name: sites
    roots:
      - "root = {{ ansible_env.HOME }}/sites"
      - "root = ssh://luxor/{{ ansible_env.USER }}/sites"
    opt: "-auto"
  - name: projects
    roots:
      - "root = {{ ansible_env.HOME }}/projects"
      - "root = ssh://luxor/{{ ansible_env.USER }}/projects"
    opt: "-auto"

and you want to reference the first root element of the job named projects.
Notice that I want to reference the dicts by its name value and not by its index number (so not simply unison_jobs[n]).

This is not that hard, but enough time passes between occurrences that I forget the specifics and have to look it up again. I hope by writing it down that I will strengthen my ability to recall, or at least give myself a fixed spot to look for it.

{{ unison_jobs | selectattr('name, 'equalto', 'projects') | map(attribute='roots') | first }}

How does map(attribute='somekey') work? Does it return a list even if the referenced key is a non-list item? Yes, by default it always returns a list. Does that mean we can set some option to disable that behaviour? Does not look like it, no.

• https://stackoverflow.com/a/31896249 - Ansible: filter a list by its attributes
• https://jinja.palletsprojects.com/en/stable/templates/#jinja-filters.map - I don't see any option that would force the returned value to be scalar (i.e., not list)
• https://old.reddit.com/r/ansible/comments/pqkom8/jinja_filtering_or_how_i_learned_to_filter - a very nice explainer on how to use Jinja filters such as select, selectattr, and map
• https://www.middlewareinventory.com/blog/ansible-map
• https://stackoverflow.com/questions/71351075/selectattr-returns-generator-rows-and-cannot-use-results-as-a-dict - selectattr() returns generator object by default
• https://github.com/pallets/jinja/issues/288 - map() filter returns generator object by default
• https://www.ansiblepilot.com/articles/filtering-data-in-ansible-selectattr-and-map