[GitHub] [arrow] paleolimbot commented on a diff in pull request #33858: GH-15054: [C++] Change s3 finalization to happen after arrow threads finished, add pyarrow exit hook

["paleolimbot (via GitHub)" <gi...@apache.org>]

paleolimbot commented on code in PR #33858:
URL: https://github.com/apache/arrow/pull/33858#discussion_r1167209940


##########
r/R/arrow-package.R:
##########
@@ -147,6 +153,12 @@ supported_dplyr_methods <- list(
   # Register extension types that we use internally
   reregister_extension_type(vctrs_extension_type(vctrs::unspecified()))
 
+  # Registers a callback to run at session exit
+  .onLoad <- function(libname, pkgname) {
+    print(parent.env(environment()))
+    reg.finalizer(parent.env(environment()), finalize_s3, onexit=TRUE)
+  }
+

Review Comment:
   I know you asked about this earlier and found `.onUnload()`...just putting a note here in case this gets forgotten about.
   
   If `.onUnload()` isn't working you can create your own environment an register a finalizer on that:
   
   ```r
   s3_finalizer <- new.env(parent = emptyenv())
   
   .onLoad <- function(...) {
     # ...
     reg.finalizer(s3_finalizer, finalize_s3, onexit=TRUE)
   }
   ```
   
   You probably shouldn't register a finalizer on the package namespace because somebody else might have done that (maybe even R).



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