Load library into existing environment (equivalent to "local" parameter of "source")? - r

Question

I am sourcing util functions in production into an environment to encapsulate (and group) the helper functions:
Helper file:
# File: Helper.R
hello <- function() {
print("Hello world")
}
Client:
helper <- new.env()
source("Helper.R", local=helper)
helper$hello() # call the helper function
How can I migrate my sourced "Helper.R" into a library without breaking the calls of the sourced functions?
What I want is something like
helper <- new.env()
library(Helper, local=helper)
helper$hello() # call the helper function (loaded from the library now)
Is there a way to do this?

Answer 1

You can use the box::use() function in the ‘box’ package.
Then the following attaches a package locally:
box::use(pkg[...])
Alternatively, and potentially closer to what you actually want to do, you could use the following simpler code:
box::use(pkg)
Now the package is not attached at all, and its exported objects can be accessed via pkg$obj. This is somewhat similar to base R’s loadNamespace function, but does considerably more behind the scenes.
Finally, consider not putting your helper code into a package at all, but rather distributing it as a module. This is after all what the ‘box’ package was designed for: instead of creating a package, just distribute your helper.r code file (or folder) and then use it as follows:
box::use(./helper)
See the package website and vignette for a detailed description.

Answer 2

Adding to the list of suggestions you can also consider to use the modules package on CRAN (note I am the author). When you have your Helper.R file with:
hello <- function() {
print("Hello world")
}
you can use
helper <- modules::use("Helper.R")
helper$hello()
to encapsulate your helper functions in their own environment. The package also provides some functions to manipulate the local namespace of a module (imports/exports).

Answer 3

I have found another package called import (similar to "modules") that allows importing packages into an environment:
https://github.com/smbache/import
This package is also on CRAN:
install.packages("import")
It allows importing selected, all exported ("public") or all (even not exported) functions of a package.
Example:
import::from(dplyr, arrange, .into = "datatools")
The import::from function is a convenient wrapper around getExportedValue.

Answer 4

Another way could be:
# getNamespace returns the environment representing the name space name. The namespace is loaded if necessary.
# Internal function to support reflection on namespace objects!
env <- getNamespace("data.table")
cars <- env$as.data.table(mtcars)
This examples makes all objects of the package data.table available via the environment variable env.
Note: It uses an internal R function (I have no idea how big the risk of changes of this internal function really is).