Entire global environment getting passed along with user-defined (global) functions in shiny

[ismirsehregal]

Describe the bug

When calling a global function in a future (_promise) the entire global environment is getting passed along with the user-defined function. This, in a shiny context, also includes the server and the ui function, which depending on the apps size results in a long processing time.

This might be a regression (or promises::future_promise()'s behaviour?).

Reproduce example

library(future)
library(shiny)
library(bslib)
library(promises)
library(future.mirai)

plan(future.mirai::mirai_multisession)

some_other_global_var <- 1L

# size: 21750
# global_function <- local(function(){
#   # Slow operation
#   Sys.sleep(2)
#   sample(1:100, 1)
# })

# size: 418991
global_function <- function(){
  # Slow operation
  Sys.sleep(2)
  sample(1:100, 1)
}

ui <- page_fluid(
  titlePanel("Extended Task Demo"),
  p(
    'Click the button below to perform a "calculation"',
    "that takes a while to perform."
  ),
  input_task_button("recalculate", "Recalculate"),
  p(textOutput("result"))
)

server <- function(input, output) {
  rand_task <- ExtendedTask$new(function() {
    print(environment(global_function))
    print(ls(environment(global_function)))
    print(future:::objectSize(global_function))
    future_promise(
      {
        global_function()
      }, seed = 1L
    )
  })
  
  bind_task_button(rand_task, "recalculate")
  
  observeEvent(input$recalculate, {
    # Invoke the extended in an observer
    rand_task$invoke()
  })
  
  output$result <- renderText({
    number <- rand_task$result()
    paste0("Your number is ", number, ".")
  })
}

shinyApp(ui, server)

Expected behavior

Passing only the needed objects.

Session information

R version 4.6.0 (2026-04-24 ucrt)
Platform: x86_64-w64-mingw32/x64
Running under: Windows 10 x64 (build 19045)

Matrix products: default
  LAPACK version 3.12.1

locale:
[1] LC_COLLATE=German_Germany.utf8  LC_CTYPE=German_Germany.utf8    LC_MONETARY=German_Germany.utf8 LC_NUMERIC=C                   
[5] LC_TIME=German_Germany.utf8    

time zone: Europe/Berlin
tzcode source: internal

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

other attached packages:
[1] future.mirai_1.0.0 promises_1.5.0     bslib_0.11.0       future_1.70.0      shiny_1.14.0      

loaded via a namespace (and not attached):
 [1] jsonlite_2.0.0    compiler_4.6.0    Rcpp_1.1.1-1.1    parallel_4.6.0    later_1.4.8       jquerylib_0.1.4   globals_0.19.1    fastmap_1.2.0    
 [9] mime_0.13         R6_2.6.1          nanonext_1.9.1    tibble_3.3.1      mirai_2.7.1       pillar_1.11.1     rlang_1.2.0       cachem_1.1.0     
[17] httpuv_1.6.17     fs_2.1.0          sass_0.4.10       otel_0.2.0        memoise_2.0.1     cli_3.6.6         withr_3.0.3       magrittr_2.0.5   
[25] digest_0.6.39     rstudioapi_0.19.0 fontawesome_0.5.3 xtable_1.8-8      lifecycle_1.0.5   vctrs_0.7.3       glue_1.8.1        listenv_1.0.0    
[33] codetools_0.2-20  parallelly_1.47.0 pkgconfig_2.0.3   tools_4.6.0       htmltools_0.5.9  
…
*** Package versions
future 1.70.0, parallelly 1.47.0, parallel 4.6.0, globals 0.19.1, listenv 1.0.0

*** Allocations
availableCores():
           system /proc/self/status 
                4                 4 
availableWorkers():
$system
[1] "localhost" "localhost" "localhost" "localhost"


*** Settings
- future.plan=<not set>
- future.fork.multithreading.enable=<not set>
- future.globals.maxSize=<not set>
- future.globals.onReference=<not set>
- future.resolve.recursive=<not set>
- future.rng.onMisuse=<not set>
- future.wait.timeout=<not set>
- future.wait.interval=<not set>
- future.wait.alpha=<not set>
- future.startup.script=<not set>

*** Backends
Number of workers: 4
List of future strategies:
1. mirai_multisession:
   - args: function (..., workers = availableCores(), envir = parent.frame())
   - tweaked: FALSE
   - call: plan(future.mirai::mirai_multisession)

*** Basic tests
Main R session details:
   pid     r sysname release     version nodename machine   login    user effective_user
1 8372 4.6.0 Windows  10 x64 build 19045  host001  x86-64 user001 user001        user001
…