Fix #807

Author: wlandau

NEWS.md

@@ -10,6 +10,7 @@
 
 * Add Google Cloud Storage via `tar_target(..., repository = "gcp")` (#720, @markedmondson1234). Special thanks to @markedmondson1234 for the cloud storage utilities in `R/utils_gcp.R`
 * `mermaid.js` static graphs with `tar_mermaid()` (#775, @yonicd).
+* Implement `tar_target(..., error = "null")`to allow errored targets to return `NULL` and continue (#807, @zoews). Errors are still registered, those targets are not up to date, and downstream targets have an easier time continuing on.
 * Implement `tar_assert_finite()`.
 * `tar_destroy()`, `tar_delete()`, and `tar_prune()` now attempt to delete cloud data for the appropriate targets (#799). In addition, `tar_exist_objects()` and `tar_objects()` now report about target data in the cloud when applicable. Add a new `cloud` argument to each function to optionally suppress this new behavior.
 * Add a `zoom_speed` argument to `tar_visnetwork()` and `tar_glimpse()` (#749, @dipterix).

R/class_builder.R

@@ -305,6 +305,7 @@ builder_handle_error <- function(target, pipeline, scheduler, meta) {
     continue = builder_error_continue(target, scheduler),
     abridge = scheduler$abridge(target),
     stop = builder_error_exit(target, pipeline, scheduler, meta),
+    null = builder_error_null(target, pipeline, scheduler, meta),
     workspace = builder_error_exit(target, pipeline, scheduler, meta)
   )
 }
@@ -326,6 +327,17 @@ builder_error_exit <- function(target, pipeline, scheduler, meta) {
   tar_throw_run(target$metrics$error)
 }
 
+builder_error_null <- function(target, pipeline, scheduler, meta) {
+  target_ensure_buds(target, pipeline, scheduler)
+  record <- target_produce_record(target, pipeline, meta)
+  record$data <- "error"
+  meta$insert_record(record)
+  target_patternview_meta(target, pipeline, meta)
+  pipeline_register_loaded(pipeline, target_get_name(target))
+  scheduler$progress$register_errored(target)
+  scheduler$reporter$report_errored(target, scheduler$progress)
+}
+
 builder_ensure_workspace <- function(target, pipeline, scheduler, meta) {
   if (builder_should_save_workspace(target)) {
     builder_save_workspace(target, pipeline, scheduler, meta)
@@ -371,15 +383,15 @@ builder_update_build <- function(target, envir) {
 }
 
 builder_resolve_object <- function(target, build) {
-  if (metrics_terminated_early(target$metrics)) {
+  if (!builder_should_save(target)) {
     return(build$object)
   }
   store_assert_format(target$store, build$object, target_get_name(target))
   store_convert_object(target$store, build$object)
 }
 
 builder_ensure_paths <- function(target, path_store) {
-  if (!metrics_terminated_early(target$metrics)) {
+  if (builder_should_save(target)) {
     tryCatch(
       builder_update_paths(target, path_store),
       error = function(error) builder_error_internal(target, error, "_paths_")
@@ -413,10 +425,15 @@ builder_update_object <- function(target) {
   store_upload_object(target$store)
 }
 
+builder_should_save <- function(target) {
+  error_null <- identical(target$settings$error, "null") &&
+    metrics_has_error(target$metrics)
+  !metrics_terminated_early(target$metrics) || error_null
+}
+
 builder_ensure_object <- function(target, storage) {
   context <- identical(target$settings$storage, storage)
-  completed <- !metrics_terminated_early(target$metrics)
-  if (context && completed) {
+  if (context && builder_should_save(target)) {
     tryCatch(
       builder_update_object(target),
       error = function(error) builder_error_internal(target, error, "_store_")

R/class_options.R

@@ -414,7 +414,10 @@ options_class <- R6::R6Class(
     },
     validate_error = function(error) {
       deprecate_error_workspace(error)
-      tar_assert_flag(error, c("stop", "continue", "abridge", "workspace"))
+      tar_assert_flag(
+        error,
+        c("stop", "continue", "abridge", "workspace", "null")
+      )
     },
     validate_memory = function(memory) {
       tar_assert_flag(memory, c("persistent", "transient"))

R/class_settings.R

@@ -148,7 +148,10 @@ settings_validate <- function(settings) {
     settings$dimensions
   )
   tar_assert_chr(settings$iteration)
-  tar_assert_in(settings$error, c("stop", "continue", "abridge", "workspace"))
+  tar_assert_in(
+    settings$error,
+    c("stop", "continue", "abridge", "workspace", "null")
+  )
   tar_assert_in(settings$memory, c("persistent", "transient"))
   tar_assert_lgl(settings$garbage_collection)
   tar_assert_scalar(settings$garbage_collection)

R/tar_target.R

@@ -167,6 +167,9 @@
 #'     but no new targets launch after that.
 #'   (Visit <https://books.ropensci.org/targets/debugging.html>
 #'   to learn how to debug targets using saved workspaces.)
+#'   * `"null"`: The errored target continues and returns `NULL`.
+#'     The data hash is deliberately wrong so the target is not
+#'     up to date for the next run of the pipeline.
 #' @param memory Character of length 1, memory strategy.
 #'   If `"persistent"`, the target stays in memory
 #'   until the end of the pipeline (unless `storage` is `"worker"`,

R/tar_target_raw.R

@@ -108,7 +108,10 @@ tar_target_raw <- function(
   tar_assert_format(format)
   tar_assert_repository(repository)
   tar_assert_flag(iteration, c("vector", "list", "group"))
-  tar_assert_flag(error, c("stop", "continue", "abridge", "workspace"))
+  tar_assert_flag(
+    error,
+    c("stop", "continue", "abridge", "workspace", "null")
+  )
   deprecate_error_workspace(error)
   tar_assert_flag(memory, c("persistent", "transient"))
   tar_assert_lgl(garbage_collection)

man/tar_option_set.Rd

@@ -543,3 +543,46 @@ tar_test("convert dep loading errors into runtime errors", {
   expect_equal(tar_objects(), "x3")
   expect_true(tar_read(x3))
 })
+
+tar_test("error = \"null\"", {
+  skip_on_cran()
+  tar_script({
+    library(targets)
+    f <- function(x) {
+      stopifnot(x < 1.5)
+      x
+    }
+    list(
+      tar_target(x, seq_len(2)),
+      tar_target(y, f(x), pattern = map(x), error = "null"),
+      tar_target(z, y)
+    )
+  })
+  tar_make(callr_function = NULL)
+  branches <- tar_meta(y)$children[[1]]
+  expect_equal(tar_progress(x)$progress, "built")
+  expect_equal(tar_progress(y)$progress, "errored")
+  expect_equal(tar_progress(z)$progress, "built")
+  progress <- tar_progress()
+  value <- progress$progress[progress$name == branches[1]]
+  expect_equal(value, "built")
+  value <- progress$progress[progress$name == branches[2]]
+  expect_equal(value, "errored")
+  expect_equal(tar_read(x), seq_len(2))
+  expect_equal(unname(tar_read(y)), 1L)
+  expect_equal(unname(tar_read(z)), 1L)
+  expect_equal(tar_read_raw(branches[1]), 1)
+  expect_null(tar_read_raw(branches[2]))
+  expect_equal(tar_errored(), sort(c("y", branches[2])))
+  out <- tar_outdated(branches = TRUE, callr_function = NULL)
+  expect_equal(sort(out), sort(c("y", "z", branches[2])))
+  tar_make(callr_function = NULL)
+  expect_equal(tar_progress(x)$progress, "skipped")
+  expect_equal(tar_progress(y)$progress, "errored")
+  expect_equal(tar_progress(z)$progress, "skipped")
+  progress <- tar_progress()
+  value <- progress$progress[progress$name == branches[1]]
+  expect_equal(value, "skipped")
+  value <- progress$progress[progress$name == branches[2]]
+  expect_equal(value, "errored")
+})