Feature Request: Loop variable inside map filter

[alexander-schranz]

I really like that twig have a loop variable in its for loops.

It would be great to also have then in a loop with the the map filter. For example:

{% set options = (choices|map((choice) => {
   checked: (loop.first and value) and choice.value in value,
})) %}

https://twigfiddle.com/4ntrof

[m-vo]

IMHO at least for array_map there is no defined order in which the callback function should be called (although the implementation uses the canonical order). From a language design perspective, this is a good thing, because then you can potentially parallelize execution.

What about instead implementing a function that enumerates an array (inspired by Python)? This would force canonical keys or wrap elements as ['loop0' => $index, 'value' => $element]:

choices|enumerate|map((value, index) => …)
choices|enumerate|map(e => e.value…)