AFAICT R_PKG_CACHE_DIR is the highest priority env var for pak

jennybc · jennybc · commit e23189b21759 · 2026-02-11T08:13:03.000-08:00
https://github.com/r-lib/pak/blob/da1069e3cf6401be4cde33468beed67c8c248e9c/src/library/pkgcache/R/cache-dirs.R#L57-L71
diff --git a/tests/testthat/setup.R b/tests/testthat/setup.R
@@ -1,5 +1,5 @@
 # Ensure that we don't affect the user's cache when testing
 withr::local_envvar(
-  R_USER_CACHE_DIR = tempfile(),
+  R_PKG_CACHE_DIR = tempfile(),
   .local_envir = teardown_env()
 )

Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,5 @@`
`1`	`1`	`# Ensure that we don't affect the user's cache when testing`
`2`	`2`	`withr::local_envvar(`
`3`		`- R_USER_CACHE_DIR = tempfile(),`
	`3`	`+ R_PKG_CACHE_DIR = tempfile(),`
`4`	`4`	`.local_envir = teardown_env()`
`5`	`5`	`)`