[maxgrinev]

Thank you for such an insightful suggestion and deep dive into the code - this is amazing feedback! I'll definitely switch to the ${{}} syntax you suggested.

Quick clarification on _expression: we intentionally use two templating systems - Jinja {{ }} for simple variable injection, and Python *_expression for complex logic that Jinja can't handle.

Actually, since we only use Jinja for variable substitution, should I just drop it entirely? We have another version implemented in Java/JavaScript that uses simple ${var-name} syntax, and we already have Python expressions for advanced scenarios. Might be cleaner to unify on ${var-name} + Python expressions.

Given how deeply you've looked into our system, would you consider using Sequor? I can promise full support including fundamental changes like these - your technical insight would be invaluable for getting the design right early on.

[mdaniel]

I'm not the target audience for this product, but I experience the pain from folks who embed jinja2/golang in yaml every single day, so I am trying to do whatever I can to nip those problems in the bud so maybe one day it'll stop becoming the default pattern

As for "complex logic that jinja can't handle," I am not able to readily identify what that would mean given that jinja has executable blocks but I do agree with you that its mental model can make writing imperative code inside those blocks painful (e.g. {% set _ = my_dict.update({"something":"else}) %} type silliness)

it ultimately depends on whether those _expression: stanzas are always going to produce a Python result or they could produce arbitrary output. If the former, then I agree with you jinja2 would be terrible for that since it's a templating language[1]. If the latter, then using jinja2 would be a harmonizing choice so the author didn't have to keep two different invocation styles in their head at once

1: one can see that in ansible via this convolution:

  body: >-
    {%- set foo = {} -%}
    {%- for i in ... -%}
    {%- endfor -%}
    {# now emit the dict as json #}
    {{ foo | to_json }}