usage with future_map, not finding attached packages

[datapumpernickel]

Hi,

thanks for this great package, it has been very useful to me in many instances!
I am not sure if I found a bug or just a limitation of the package. I want to use the package together with future_map and once a function is memoised, the attached packages are somehow not found by the function anymore.

See the attached minimal reproducible example:

library(future)
library(furrr)
library(xml2)
library(memoise)
library(dplyr)

test_function <- function(url){
  return(read_xml(url))
}

future::plan("multisession", workers = 2)
test_data <- tibble(id = 1:10, url ="https://data.europarl.europa.eu/org/5704")

## future_map finds the package, although the external pointer is invalid because of some xml error with future_map
future_map(test_data$url, test_function)

## now lets memoise the function
test_function <- memoise::memoise(test_function)

## future_map does not find the attached xml2 package anymore
future_map(test_data$url, test_function)

## map finds it
map(test_data$url, test_function)

Hope this is the right place for this!

Session Info

R version 4.2.2 (2022-10-31 ucrt)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows Server x64 (build 14393)

Matrix products: default

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

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

other attached packages:
[1] dplyr_1.1.4   memoise_2.0.1 xml2_1.3.3    furrr_0.3.1   future_1.28.0

loaded via a namespace (and not attached):
 [1] rstudioapi_0.14   parallelly_1.32.1 magrittr_2.0.3    tidyselect_1.2.0  R6_2.5.1          rlang_1.1.2       fastmap_1.1.0    
 [8] fansi_1.0.4       globals_0.16.1    tools_4.2.2       parallel_4.2.2    utf8_1.2.3        cli_3.6.2         digest_0.6.31    
[15] tibble_3.2.1      lifecycle_1.0.3   purrr_1.0.1       vctrs_0.6.5       codetools_0.2-18  glue_1.6.2        cachem_1.0.6     
[22] compiler_4.2.2    pillar_1.9.0      generics_0.1.3    listenv_0.8.0     pkgconfig_2.0.3  

[datapumpernickel]

a quick fix is, to just add the namespaces to the functions, e.g.:

test_function <- function(url){
  return(xml2::read_xml(url))
}