Use functions of an R package loaded with load_all() in callr::r() and callr::r_bg()

Question

I'm devoloping an R package and want to run some of the functions in the package under development in the background, using callr::r() or callr::r_bg().

As an example, I created a package mytest with only one function

hello <- function() {
  print("Hello, world!")
}

Then loaded the package with pkgload::load_all(), the function to load a package in development using devtools package. After this, I can run the function in the console but not in the background using callr::r().

callr::r(function(){
  mytest::hello()
})
#> Error: callr subprocess failed: there is no package called 'mytest'
#> Type .Last.error.trace to see where the error occurred

On the other hand, if I install the package and run library(mytest), the code above run without problems

callr::r(function(){
  mytest::hello()
})
#> [1] "Hello, world!"

Please, any clue why callr::r() does not find function mytest::hello()?

It looks like load_all() is not adding the path to the folder where the source code of the package mytest can be found.

Answer 1

I found a solution based on an issue in callr GitHub.

After loading the package mytest, that only has the function hello() in it as defined in the question, with devtools::load_all() the following code works

z <- list(mytest::hello)

callr::r(function(z){
  z[[1]]()
}, args = list(z))
#> [1] "Hello, world!"

It looks like the function hello() in the package loaded with load_all() cannot be referred as mytest::hello() in callr::r() or in callr::r_bg() while you can do so if the package was installed and loaded after through library(mytest).

Another option may be to install the new package in the new process started by {callr}:

callr::r(function(){
  devtools::install("./")
  mytest::hello()
})
#> [1] "Hello, world!"

Please, is there another solution that can be used to iterate the new package development using load_all() and use those package functions in a new R session open by {callr}?