[BUGZILLA #17807] parRapply and parCapply return a list in corner cases

[github-actions]

According to ?parCapply:

parRapply and parCapply always return a vector.

This appears not to be the case in the following minimal reproducible example:

library(parallel)
nslaves <- 2
cl      <- makeCluster(nslaves)
X       <- matrix(2,nrow=3,ncol=4)
X       <- rbind(c(1,1,0,1),X)
tv <- parCapply(cl,X,FUN=function(x){

+ ind <- x[1]
+ y <- x[-1]
+ if(ind==1){
+ r1 <- sum(y)
+ }else{
+ r1 <- logical(0)
+ }
+ return(unlist(as.numeric(c(ind,r1))))
+ })

tv

[[1]]
[1] 1

[[2]]
[1] 6

[[3]]
[1] 1

[[4]]
[1] 6

[[5]]
[1] 0

[[6]]
[1] 1 6

class(tv)

[1] "list"

sessionInfo()

R version 4.0.0 (2020-04-24)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 18363)

Matrix products: default

locale:
[1] LC_COLLATE=Italian_Italy.1252 LC_CTYPE=Italian_Italy.1252
[3] LC_MONETARY=Italian_Italy.1252 LC_NUMERIC=C
[5] LC_TIME=Italian_Italy.1252

attached base packages:
[1] parallel stats graphics grDevices utils datasets
methods base

loaded via a namespace (and not attached):
[1] compiler_4.0.0

Kind regards

Simone

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METADATA

• Bug author - Simone Giannerini
• Creation time - 2020-05-22 07:14:25 UTC
• Bugzilla link
• Status - UNCONFIRMED
• Alias - None
• Component - Low-level
• Version - R 4.0.0
• Hardware - All All
• Importance - P5 major
• Assignee - R-core
• URL -
• Modification time - 2020-05-22 07:46 UTC

[github-actions]

NA

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METADATA

• Comment author - Simone Giannerini
• Timestamp - 2020-09-12 09:07:05 UTC

[github-actions]

NA

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METADATA

• Comment author - Sebastian Meyer
• Timestamp - 2020-09-12 16:08:06 UTC

[github-actions]

NA

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METADATA

• Comment author - Simone Giannerini
• Timestamp - 2020-09-13 08:29:16 UTC

[github-actions]

NA

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METADATA

• Comment author - Sebastian Meyer
• Timestamp - 2020-09-13 20:04:06 UTC