Why do you invisibly return NULL in .onLoad

howardbaek · July 31, 2023, 10:31pm

I've noticed that .onLoad() functions inside dplyr and googlesheets both return NULL invisibly: invisible()

Why is this the case?

Gabor · August 1, 2023, 9:40am

You would need to ask the people writing that code to be sure. My guess is that it is a note for future code readers that "this function does not return anything useful".

I am pretty sure that it does not matter at all, R does not use the return value of .onLoad() for anything, as far as I can tell. It is called here:

github.com

wch/r-source/blob/6a12acc6ecb8fc87df5df946af2982436a85db00/src/library/base/R/namespace.R#L629


      
                      setNamespaceInfo(env, "DLLs", dlls)
                  }
                  addNamespaceDynLibs(env, nsInfo$dynlibs)
                  setNamespaceInfo(env, "nativeRoutines", nativeRoutines)
          
          
        ## used in e.g. utils::assignInNamespace
                  Sys.setenv("_R_NS_LOAD_" = package)
                  on.exit(Sys.unsetenv("_R_NS_LOAD_"), add = TRUE)
                  ## run the load hook
          	if(lev > 1L) message("-- running .onLoad for ", dQuote(package))
                  runHook(".onLoad", env, package.lib, package)
          	if(lev > 1L) message("-- done running .onLoad for ", dQuote(package))
          
          
        ## process exports, seal, and clear on.exit action
                  exports <- nsInfo$exports
          
          
        for (p in nsInfo$exportPatterns)
                      exports <- c(ls(env, pattern = p, all.names = TRUE), exports)
                  ##
                  if(.isMethodsDispatchOn() &&
                     !(hasS4m <- methods:::.hasS4MetaData(ns)) &&

howardbaek · August 1, 2023, 7:26pm

Thanks for your reply and sharing the source code, Gabor. I was just curious about both dplyr and googlesheets returning NULL and I guess it was a personal choice, not really a technical choice.

system · August 8, 2023, 7:26pm

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