[R] How to perform package cleanup when R session is ending?

[Jiefei Wang]

Thank you! This solution works! I actually tried reg.finalizer but it
didn't work when it is a part of the package code,
so I thought this is not the right function. Your example is very helpful.
Putting the function inside the package
initializer makes the finalizer works as I wish. Not sure why it behaves
differently when in different locations but
this is good enough for me. Many thanks!

Best,
Jiefei

On Sat, Dec 19, 2020 at 1:09 AM Bill Dunlap <williamwdunlap using gmail.com>
wrote:

> E.g., as in a package containing just the following R code:
>
> $ cat testFinalizer/R/zzz.R
> envir <- new.env()
> cleanup <- function(e) {
>     message("cleanup(", format(e), ")")
>     if (!isTRUE(envir$cleaned)) {
>         message("    cleaning ", format(e))
>         envir$cleaned <- TRUE
>     } else {
>         # cleanup previously called by .onUnload()
>         message("    ", format(e), " has already been cleaned")
>     }
> }
> .onLoad <- function(libname, pkgname) {
>     message("Loading ", pkgname, " from ", libname)
>     reg.finalizer(e=envir, f=cleanup, onexit=TRUE)
>     message("Installed finalizer for ", format(envir))
> }
> .onUnload <- function(libpath) {
>     message("Unloading ", libpath)
>     cleanup(envir)
> }
>
> This gives:
>
> $ R --quiet
> > library(testFinalizer,lib="lib")
> Loading testFinalizer from /home/bill/packages/lib
> Installed finalizer for <environment: 0x55a558b16120>
> > detach("package:testFinalizer", unload=TRUE)
> Unloading /home/bill/packages/lib/testFinalizer
> cleanup(<environment: 0x55a558b16120>)
>     cleaning <environment: 0x55a558b16120>
> > q("no")
> cleanup(<environment: 0x55a558b16120>)
>     <environment: 0x55a558b16120> has already been cleaned
> $ R --quiet
> > library(testFinalizer, lib="lib")
> Loading testFinalizer from /home/bill/packages/lib
> Installed finalizer for <environment: 0x55f8dac2d598>
> > objects(all=TRUE)
> character(0)
> > q("no")
> cleanup(<environment: 0x55f8dac2d598>)
>     cleaning <environment: 0x55f8dac2d598>
>
> On Fri, Dec 18, 2020 at 7:39 AM Bill Dunlap <williamwdunlap using gmail.com>
> wrote:
>
>> Have you tried using reg.finalizer(..., onexit=TRUE)?
>>
>> -BIll
>>
>> On Fri, Dec 18, 2020 at 7:29 AM Jiefei Wang <szwjf08 using gmail.com> wrote:
>>
>>> Hi,
>>>
>>> I am looking for a way to clean up my package resources before R is
>>> ended.
>>> It looks like the .onUnload function would not be helpful as it would not
>>> be called before R is ended. This behavior has been described in the
>>> document:
>>>
>>> *Note that packages are not detached nor namespaces unloaded at the end
>>> of
>>> an R session unless the user arranges to do so (e.g., via .Last).*
>>>
>>> I have also searched for ?.Last as the document says. However, the .Last
>>> function is for the end user to use, not for the package developers, so I
>>> am clueless now. How to clean up my package before R ends? Any
>>> suggestions?
>>>
>>> Best,
>>> Jiefei
>>>
>>>         [[alternative HTML version deleted]]
>>>
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>>

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