Using tar_map inside a target factory

[ablack3]

I would like to use tar_map in a target factory so I think I need a "raw" version of the function.

I see tar_map2_raw as well as tar_map_rep_raw but no tar_map_raw.

Can tar_map be used in a target factory?

[ablack3]

I think I understand a bit more now. tar_map can be used in a factory if tar_target_raw is used inside the tar_map call.

[wlandau]

Yeah, tar_map() works well inside target factories once you have the template target objects. Packages jagstargets and stantargets work like this.

[nopsybot]

I have a follow-up question for this scenario:
How should the tar_map()'s values argument be expressed, when values is a dependency-tracked target_object itself and generated beforehand outside the factory? See this situation:

targets::tar_script({
  
  target_fty <- function( .values_tgt ){
    tarchetypes::tar_map(
      values = .values_tgt,
      names = id,
      targets::tar_target_raw("results",quote(x+y))
    )
  }

  list(
    tar_target(
      values_tgt,
      list(id = c("a","b","c"),x=quote(c(1,2,3)),y=quote(c(4,5,6)))
    ),
    target_fty( .values_tgt=values_tgt )
    )

})

targets::tar_manifest()
#> Error:
#> ! Error running targets::tar_manifest()
#>   Error messages: targets::tar_meta(fields = error, complete_only = TRUE)
#>   Debugging guide: https://books.ropensci.org/targets/debugging.html
#>   How to ask for help: https://books.ropensci.org/targets/help.html
#>   Last error: object 'values_tgt' not found
#> Backtrace:
#>     ▆
#>  1. └─targets::tar_manifest()
#>  2.   └─targets:::callr_outer(...)
#>  3.     ├─targets:::if_any(...)
#>  4.     └─targets:::callr_error(condition = out, fun = fun)
#>  5.       └─targets::tar_throw_run(message, class = class(condition))
#>  6.         └─targets::tar_error(...)
#>  7.           └─rlang::abort(message = message, class = class, call = tar_empty_envir)

^{Created on 2023-08-31 with reprex v2.0.2}

I just don't get it this object transmission meta-programmed.
I tried to quote() at different levels.
target_fty( .values_tgt = tar_read(values_tgt) ) would ignore the dependency.

Many thanks!

[wlandau]

values cannot be a target because tar_map() uses static branching. That means the branching structure needs to be fully determined before the pipeline starts. If you need to branch based on the value of an upstream target, that is called dynamic branching. I recommend looking at both chapters.

[nopsybot]

Thank you. This brings me back on track =)