How to avoid namespace ambiguity for user defined functions

Question

Avoiding potential unambiguity from namespace collisions for functions that come from libraries can be achieved by prepending the package name to the function call (e.g. dplyr::left_join, plyr::left_join etc), as explained here

How can this unambiguity be achieved for a user defined function? (i.e. one that did not come from a library/package). Obviously you cannot prepend the package name to a function if the function did not come from a package

Example

library(dplyr)
left_join <- function(x, y) { x + y }

dplyr::left_join(x,y) # Unambiguously calls left_join from dplyr
left_join(x, y) # Not clear whether from dplyr or user defined

How can user defined functions be called unambiguously?

Answer 1

Here is a dummy function I have written. I have not rigorously tested it so it might break:

import_from_global<-function(what,...){
  func<-get(what,envir=.GlobalEnv) 
  do.call(func,list(...))
}

Test:

select<-function(){
  cat("using namespace .GlobalEnv\n") 
  print("Does nothing")
}
import_from_global("select")

Result:

using namespace .GlobalEnv
[1] "Does nothing"