fake package

fake_package

fake_package <- function(name, exported = NULL, unexported = NULL, attach = TRUE) {
  # fetch and eval call to create `makeNamespace`
  eval(body(loadNamespace)[[c(8, 4, 4)]])
  # create an empty namespace
  ns <- makeNamespace(name)
  # makethis namespace the closure env of our input functions
  exported <- lapply(exported, `environment<-`, ns)
  unexported <- lapply(unexported, `environment<-`, ns)
  # place these in the namespace
  list2env(exported, ns)
  list2env(unexported, ns)
  # export relevant functions
  namespaceExport(ns, names(exported))
  if(attach) {
    # copy exported funs to "package:pkg" envir of the search path
    attach(exported, name = paste0("package:", name))
  }
  invisible()
}

fake_package(
  "fake",
  exported = list(add_2 = function(x) add_1(x) + 1),
  unexported = list(add_1 = function(x) x + 1))

# the search path looks as it would after a library call
search()
#>  [1] ".GlobalEnv"        "package:fake"      "package:stats"    
#>  [4] "package:graphics"  "package:grDevices" "package:utils"    
#>  [7] "package:datasets"  "package:methods"   "Autoloads"        
#> [10] "tools:callr"       "package:base"

# add_2 was exported
add_2
#> function(x) add_1(x) + 1
#> <environment: namespace:fake>

fake::add_2
#> function(x) add_1(x) + 1
#> <environment: namespace:fake>

fake:::add_2
#> function(x) add_1(x) + 1
#> <environment: namespace:fake>

# add_1 was not, so as expected can't be found
add_1
#> Error: object 'add_1' not found

fake::add_1
#> Error: 'add_1' is not an exported object from 'namespace:fake'

fake:::add_1
#> function(x) x + 1
#> <environment: namespace:fake>

# let's try it
add_2(3)
#> [1] 5