736 Allow pure custom card functions in modules

[chlebowa]

Solves #736.
Alternative to #737.
Accompanied by insightsengineering/teal.reporter#270.
Allows custom card functions to be pure functions.

Card functions must receive an environment in argument env, which contains all elements to which the card function will refer when building a report card.

A card function will now look like this (note the env$):

local_card_function <- function(comment, label, env) {
  card <- teal::report_card_template(
    title = "Distribution Plot",
    label = label,
    with_filter = env$with_filter,              # env$ here
    filter_panel_api = env$filter_panel_api     # env$ here
  )
  card$append_text("Dummy Card", "header2")
  card$append_text(paste(
    "This report card was generated by a card function",
    "defined in the global environment."
  ))
  if (!comment == "") {
    card$append_text("Comment", "header3")
    card$append_text(comment)
  }
  card
}

[github-actions]

CLA Assistant Lite bot ✅ All contributors have signed the CLA

[chlebowa]

I have read the CLA Document and I hereby sign the CLA

[gogonzo]

I think this is something we need to rethink (the way how to handle custom reporting)

---

I think there are two ways to handle this:

1. One you described above where custom function passed through argument is executed in the srv environment, or
2. module returns reporter card (and other elements) and one can wrap function around srv to bypass and edit reporter card on the fly. (I guess this is not possible now and require some refactoring)

(1) is related with the idea we are currently exploring which is called "preprocessing", where app developer can pass any code/function to the srv and "postprocess" existing items in that environment.

[chlebowa]

It seems to me the solution you are proposing involves a significant rewrite of the modules as well as the framework. In the long run it is probably superior but I imagine it would take time to properly design and implement.
The solution proposed here is quicker to implement and introduces the feature of custom reporting without changing the framework in a meaningful way. It can be used as a temporary measure. I imagine that if a module returns something (be it a TealReportCard object or a list of its possible contents), the way to specify its handling would be to pass a function.

I will be happy to discuss further.