Where to load packages when sourcing an R script

Question

I have two R scripts. scriptB is called in scriptA via source("scriptB.R")

both scriptA and scriptB load the same library(x) where x is knitr or stringr or a few other packages

However, because scriptB calls library(x) for example, it seems scriptA is forced to unload its library(x) and then load up the scriptB library(x) . This leads to the following error:

Error in unloadNamespace(package) : 
  namespace 'x' is imported by 'y' so cannot be unloaded
Error in library(x) : Package 'x' version n.nn cannot be unloaded

I don't actually call unloadNamespace in the source script so I'm not sure why this is happening? How can I prevent the unload. Should I just use require() in scriptA so it can fail gracefully?

So my questions are:

1. Is sourcing the R script the best way to include objects from the R script or is there a friendlier way

2. How do I avoid the script from trying to unload package x?

Answer 1

OK I sorted it. The problem I think was I was using old versions of stringr in scriptA or B so I updated the package and now it runs fine. I suppose R unloads the same library if there is a versioning difference and probably prefers the library that is called last. That's my only explanation.

I remain a little confused however as I didn't specify a version of the library when loading it and I though rstudio only keeps one version of a package.