tar_cue_skip: Cue to skip a target if a condition is true

In wlandau/tarchetypes: Archetypes for Targets

Cue to skip a target if a condition is true

Description

tar_cue_skip() creates a cue object to skip a target if an arbitrary condition evaluates to TRUE. The target still builds if it was never built before. Supply the returned cue object to the cue argument of targets::tar_target() or similar.

Usage

tar_cue_skip(
  condition,
  command = TRUE,
  depend = TRUE,
  format = TRUE,
  repository = TRUE,
  iteration = TRUE,
  file = TRUE
)

Arguments

condition	Logical vector evaluated locally when the target is defined. If any element of condition is TRUE, the pipeline will skip the target unless the target has never been built before. If all elements of condition are FALSE, then the target may or may not rerun, depending on the other invalidation rules. condition is evaluated when this cue factory is called, so the condition cannot depend on upstream targets, and it should be quick to calculate.
command	Logical, whether to rerun the target if command changed since last time.
depend	Logical, whether to rerun the target if the value of one of the dependencies changed.
format	Logical, whether to rerun the target if the user-specified storage format changed. The storage format is user-specified through tar_target() or tar_option_set().
repository	Logical, whether to rerun the target if the user-specified storage repository changed. The storage repository is user-specified through tar_target() or tar_option_set().
iteration	Logical, whether to rerun the target if the user-specified iteration method changed. The iteration method is user-specified through tar_target() or tar_option_set().
file	Logical, whether to rerun the target if the file(s) with the return value changed or at least one is missing.

Value

A cue object. See the "Cue objects" section for background.

Cue objects

A cue object is an object generated by targets::tar_cue(), tarchetypes::tar_cue_force(), or similar. It is a collection of decision rules that decide when a target is invalidated/outdated (e.g. when tar_make() or similar reruns the target). You can supply these cue objects to the tar_target() function or similar. For example, tar_target(x, run_stuff(), cue = tar_cue(mode = "always")) is a target that always calls run_stuff() during tar_make() and always shows as invalidated/outdated in tar_outdated(), tar_visnetwork(), and similar functions.

See Also

Other cues: tar_age(), tar_cue_age(), tar_cue_force()

Examples

if (identical(Sys.getenv("TAR_LONG_EXAMPLES"), "true")) {
targets::tar_dir({ # tar_dir() runs code from a temporary directory.
targets::tar_script({
  library(tarchetypes)
  list(
    targets::tar_target(
      data,
      data.frame(x = seq_len(26)),
      cue = tarchetypes::tar_cue_skip(1 > 0)
    )
  )
})
targets::tar_make()
targets::tar_script({
  library(tarchetypes)
  list(
    targets::tar_target(
      data,
      data.frame(x = seq_len(25)), # Change the command.
      cue = tarchetypes::tar_cue_skip(1 > 0)
    )
  )
})
targets::tar_make()
targets::tar_make()
})
}

wlandau/tarchetypes documentation built on Dec. 8, 2024, 4:44 p.m.