Possible bug: tar_age() does not work in tar_map()

[psychelzh]

Help

• I understand and agree to https://books.ropensci.org/targets/help.html.

Description

A simple example:

targets::tar_dir({
  targets::tar_script({
    library(targets)
    targets <- tarchetypes::tar_map(
      values = data.frame(x = 1:2),
      list(
        tarchetypes::tar_age(
          test, x,
          age = as.difftime(1, units = "days")
        )
      )
    )
    list(
      targets,
      tarchetypes::tar_age(x, 1, age = as.difftime(1, units = "days"))
    )
  })
  targets::tar_make()
  targets::tar_make()
})
#> • start target x
#> • built target x [0 seconds]
#> • start target test_1
#> • built target test_1 [0 seconds]
#> • start target test_2
#> • built target test_2 [0 seconds]
#> • end pipeline [0.08 seconds]
#> ✔ skip target x
#> • start target test_1
#> • built target test_1 [0 seconds]
#> • start target test_2
#> • built target test_2 [0 seconds]
#> • end pipeline [0.11 seconds]

^{Created on 2023-05-09 with reprex v2.0.2}

[wlandau]

tar_age() uses tar_cue_age_raw() to create the cue, and this cue is specific to the original target object with the original name before mapping occurs. tar_map() does not update cues, so tar_eval() would be a better fit for this case: https://books.ropensci.org/targets/static.html#metaprogramming

[psychelzh]

Thank you very much! Reasonable, though tar_map() is very useful to create multiple many targets for each row. Some effort to shift mental model to use tar_eval() could make it work.

[psychelzh]

Found an issue for tar_eval(). It will substitute the namespace if I use a namespaced call:

targets::tar_dir({
  writeLines(
    "
default:
  name: value
dev:
  name: value1
    ",
    "config.yml"
  )
  targets::tar_script({
    library(targets)
    list(
      tarchetypes::tar_eval(
        tar_target(
          name,
          config::get("name", config = config)
        ),
        values = list(config = "dev")
      )
    )
  })
  targets::tar_manifest()
})
#> # A tibble: 1 × 2
#>   name  command                                   
#>   <chr> <chr>                                     
#> 1 name  "\"dev\"::get(\"name\", config = \"dev\")"

^{Created on 2023-05-10 with reprex v2.0.2}

Maybe this is just the issue with substitue()? For example:

substitute(config::get("name", config = config), env = list(config = "dev"))
#> "dev"::get("name", config = "dev")

^{Created on 2023-05-10 with reprex v2.0.2}

Possibly I need this workaround:

targets::tar_dir({
  writeLines(
    "
default:
  name: value
dev:
  name: value1
    ",
    "config.yml"
  )
  targets::tar_script({
    library(targets)
    list(
      tarchetypes::tar_eval(
        tar_target(
          name,
          `::`("config", "get")("name", config = config)
        ),
        values = list(config = "dev")
      )
    )
  })
  targets::tar_manifest()
  targets::tar_make()
  targets::tar_read(name)
})
#> • start target name
#> • built target name [0.01 seconds]
#> • end pipeline [0.09 seconds]
#> [1] "value1"

^{Created on 2023-05-10 with reprex v2.0.2}

[wlandau]

You can choose a different symbol than config, e.g.

tarchetypes::tar_eval(
  tar_target(
    name,
    config::get("name", config = my_config)
  ),
  values = list(my_config = "dev")
)