Notes around continuing styler caching pain

tests/testthat/helper.R

@@ -1,5 +1,15 @@
-
-# Work around R.cache bug on CI
+# Work around some bug in R.cache and/or styler that affects CI ----
+# 2024-01: Since this went in, I have seen yet another CI failure due to what I
+# assume is this directory not existing, presumably because some code in styler
+# deleted it, after we created it here.
+# The problem seemed to go away upon further investigation, so it seems
+# somewhat stochastic.
+# See https://github.com/tidyverse/reprex/pull/455.
+# If we have to debug this again, these are some thoughts:
+# * When we forcibly create the directory, also put a file in it. That might
+#   keep styler from deleting it.
+# * Figure out how to deactivate all styler caching for reprex, at least on CI.
+#   Seems to require `options(styler.cache_name = NULL)`.
 if (getRversion() >= "4.0.0" && identical(Sys.getenv("CI"), "true")) {
   dir.create(
     tools::R_user_dir("R.cache", which = "cache"),