New format filter with value(s) as input rather than format string (to make is usable with `map` and a list of values)

[VannTen]

Summary

I would like to be able to format a list of dictionnary (or tuple, or simple items) using the same format string.

This can't be done with the jinja filter format because the string is the input / first parameters, so using with map is only useful for passing differents format string rather than differents values.

I don't have a strong opinion on the syntax (of the format string), but I think something like str.format would be simple enough ?

I'm willing to make the PR myself if the feature is considered worthwhile.

Issue Type

Feature Idea

Component Name

filters

Additional Information

# Ansible variables
list_of_docker_images:
- repo: docker.io
  image: alpine
  tag: v3.4.5
  digest: sha256:xxxxxxxxx
- repo: k8s.io
  image: kube-proxy
  tag: v1.34.0
  digest: sha256:yyyyyyyyy
list_of_full_image_names: "{{ list_of_docker_images | map('some_format_filter', '{repo}/{image}:{tag}@{digest}')
# => ['docker.io/alpine:v3.4.5@sha256:xxx', 'k8s.io/kube-proxy:v1.34.0@sha256:yyyyyyy']

Code of Conduct

• I agree to follow the Ansible Code of Conduct

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[felixfontein]

I'm wondering whether it would make sense to have some "reverse map" filter(s) that basically allows to swap sides for a filter when applied as a map, so you could do list_of_docker_images | reverse_map_as_kwarg('format', '{repo}/{image}:{tag}@{digest}') to get what you want. I remember having had similar troubles with other filters, where a usual | map would put the value into the wrong argument (but I don't remember what is was right now).

I can think of three filters that could be useful (the names are definitely up for discussion):

1. reverse_map_as_kwarg(fitler_name, *args, *kwargs): apply filter_name(*args, **kwargs, **filter_value) to all elements filter_value (which must be mappings).
2. reverse_map_one_value(filter_name, before_args, *after_args, **kwargs): apply filter_name(*before_args, filter_value, *after_args, **kwargs) to all elements filter_value.
3. reverse_map_multiple_values(filter_name, before_args, *after_args, **kwargs): apply filter_name(*before_args, *filter_value, *after_args, **kwargs) to all elements filter_value (which must be sequences).

These should cover most similar problems, but also might be a bit too general for most users...

Sorry for derailing this issue a bit ;-)

[VannTen]

No problem.

Maybe another possible approach would a flip (I'm using the name from Haskell) filter which basically reverse the argument before feeding it to it's filter argument ?

Something like some_dict | flip('format', '{repo}/{image}:{tag}') which could then easily used from map ?
I'm not sure if that's actually doable given the filter infrastrcture.

[felixfontein]

Does flip always flip the first two positional arguments? Or what does happen if there are more than two?