A future that is interrupted after being canceled is now always reported as canceled

Author: HenrikBengtsson

DESCRIPTION

@@ -1,5 +1,5 @@
 Package: future
-Version: 1.80.0-9020
+Version: 1.80.0-9021
 Title: Unified Parallel and Distributed Processing in R for Everyone
 Depends:
     R (>= 3.2.0)

NEWS.md

@@ -2,6 +2,10 @@
 
 ## Significant Changes
 
+ * A future that is interrupted after being canceled is now always
+   reported as canceled, whereas an interruption that is not caused by
+   `cancel()` is still a `FutureInterruptError`.
+
  * `digest` is no longer a hard dependency. The package now uses
    `tools::md5sum(bytes = ...)`, which is available in R (>= 4.5.0), to
    generate unique IDs for R objects. For older versions of R, it uses
@@ -12,6 +16,10 @@
 
 ## Bug Fixes
 
+ * `value()` on a future that was canceled with `cancel()` and
+   interrupted could signal a `FutureInterruptError` instead of a
+   `FutureCanceledError`, e.g. for 'multicore' futures.
+
  * When launching a 'cluster' or 'multisession' future timed out while
    waiting for an available worker, it would produce an obscure
    error instead of an informative timeout error.

R/core_api-value.R

@@ -86,7 +86,12 @@ value.Future <- function(future, stdout = TRUE, signal = TRUE, drop = FALSE, ...
     future <- run(future)
   }
 
-  result <- result(future)
+  ## An interruption of a future that was canceled is a cancellation
+  result <- withCallingHandlers(result(future), FutureInterruptError = function(ex) {
+    if (!inherits(ex, "FutureCanceledError") && "cancel" %in% future[["actions"]]) {
+      stop(canceledFutureError(future))
+    }
+  })
   stop_if_not(inherits(result, "FutureResult"))
 
   value <- result[["value"]]

R/protected_api-result.R

@@ -121,3 +121,14 @@ result.Future <- function(future, ...) {
 
   .Defunct(msg = "Future objects with an internal version of 1.7 or earlier are defunct. This error is likely coming from a third-party package or other R code. Please report this to the maintainer of the 'future' package so this can be resolved.", package = .packageName)
 }
+
+
+## Creates a FutureCanceledError for a future that was canceled, and records
+## it as the result of the future
+canceledFutureError <- function(future) {
+  msg <- sprintf("Future (%s) of class %s was canceled", sQuoteLabel(future), class(future)[1])
+  result <- FutureCanceledError(msg, future = future)
+  future[["result"]] <- result
+  future[["state"]] <- "canceled"
+  result
+}

inst/testme/test-cancel-canceled-error.R

@@ -0,0 +1,38 @@
+#' @tags cancel
+#' @tags detritus-files
+#' @tags detritus-connections
+#' @tags multisession multicore
+
+library(future)
+options(future.debug = FALSE)
+
+## A sequential future is resolved already when created, so there is
+## nothing to cancel
+strategies <- setdiff(supportedStrategies(), "sequential")
+
+for (strategy in strategies) {
+  message(sprintf("plan('%s') ...", strategy))
+  plan(strategy)
+
+  n0 <- nbrOfFreeWorkers()
+
+  ## Cancel a running future
+  f <- future({ Sys.sleep(1.0); 42 })
+  stopifnot(!resolved(f))
+  f <- cancel(f)
+
+  ## Canceled futures always triggers a FutureCanceledError,
+  ## regardless whether they were interrupted or not
+  v <- tryCatch(value(f), error = identity)
+  print(class(v))
+  stopifnot(inherits(v, "FutureCanceledError"))
+
+  ## Canceled futures always release their workers
+  stopifnot(nbrOfFreeWorkers() == n0)
+
+  message(sprintf("plan('%s') ... done", strategy))
+}
+
+message("Shut down future backend")
+plan(sequential)
+gc()

inst/testme/test-interrupts-from-worker-itself.R

@@ -47,6 +47,9 @@ for (strategy in strategies) {
   }, FutureError = identity)
   print(v)
 
+  ## An interruption that was not caused by cancel() is never a cancellation
+  stopifnot(!inherits(v, "FutureCanceledError"))
+
   ## A future interrupting itself is not supported on all backends
   stopifnot(
     #   (i) Ideally the SIGINT interrupt condition is caught, but ...

tests/test-cancel-canceled-error.R

@@ -0,0 +1,4 @@
+#! /usr/bin/env Rscript
+## This runs testme test script inst/testme/test-cancel-canceled-error.R
+## Don't edit - it was autogenerated by inst/testme/deploy.R
+future:::testme("cancel-canceled-error")