Find unused/"orphaned" non-exported objects during package development

I'm refactoring a package containing many non-exported functions and other non-exported objects. Is there a way to quickly identify all the "orphaned" objects that are defined but not exported or called anywhere else in the package, other than manually doing a full text search for the name each function in the package?

An additional complication is that some functions are called inside glue f-style strings, so there may be cases where functions are called that are not parsable as expressions (this is probably not a good design pattern).

But I would be satisfied with a method for just functions and other objects that never appear as normal expressions after being defined.

Solution

This will give you a partial answer (edited from the original):

pkg <- "testpkg"
library(pkg, character.only = TRUE)
ns <- getNamespace(pkg)
allnames <- ls(ns)
exports <- ls(paste0("package:", pkg))

nsInfo <- readRDS(system.file("Meta/nsInfo.rds", package = pkg))

if (!is.null(nsInfo$S3methods)) {
  S3methods <- with(nsInfo, paste(S3methods[,1], S3methods[,2], sep = "."))
} else
  S3methods <- NULL

locals <- setdiff(allnames, c(exports, S3methods))

used <- character()
newones <- c(exports, S3methods)
while (length(newones)) {
  mentioned <- unique(unlist(lapply(newones, function(n) {
      fun <- get(n, envir = ns)
      if (is.function(fun)) 
        codetools::findGlobals(fun)
        })))
  used <- c(used, newones)
  newones <- setdiff(intersect(mentioned, locals), used)
}
 
unused <- setdiff(locals, used)
unused

This still isn't quite right, but it should get you started. Some problems:

it assumes no functions are doing funny stuff like assign(), or fiddling with environments, etc.
it doesn't detect functions that are used entirely to build other objects in the package.
it doesn't detect weird S3 methods declared with a non-standard name.