with_temp_install()

[hadley]

There are an increasing number of places where we want to run R code in another session with the package installed. But installing is a relatively expensive operation, so it would be nice if we could minimise the times we do it. I suggest a with_temp_install() that does something like this:

with_temp_install <- function(code, pkg = ".") {
  dev_lib <- file.path(tempdir(), "dev-library")
  
  if (!file.exists(dev_lib)) {
    dir.create(dev_lib)
  }

  if (needs_install(pkg)) {
    install(pkg = pkg, quick = TRUE, reload = FALSE, dependencies = FALSE)
  }
   
  withr::with_temp_libpaths(code) 
}

hash <- new.env(parent = emptyenv())

needs_install <- function(pkg = ".") {
  # Hash R/*.R and src/*.{c,cpp} and NAMESPACE, ...
  # Compare hashes
}

(With accompanying local version too)

[hadley]

For now, I've made a simple local_install() which will re-install every time.