inst/extdata/pkgtemplate/dev/01_load_or_install.R

In cpp4r: Header-Only 'C++' and 'R' Interface

# run this line if you want to replace all the files provided by the template
# cpp11armadillo::pkg_template()

if (!requireNamespace("devtools", quietly = TRUE)) {
  install.packages("devtools")
}

development <- TRUE

devtools::clean_dll()
cpp11::cpp_register()
devtools::document()

if (isTRUE(development)) {
  devtools::load_all()
} else {
  devtools::install()
}