.onLoad` prompts for cache-directory creation via `readline()` — `library(epidatr)` fails in non-interactive sessions (Rscript/Rmd/render pipelines) when the configured directory is missing

[docxology]

Summary

While testing the documented persistent-cache workflow, I found that when EPIDATR_USE_CACHE=TRUE is set and EPIDATR_CACHE_DIR points at a directory that does not exist, .onLoad() calls set_cache(startup = TRUE) with the default confirm = TRUE, which runs an interactive readline() prompt during package load. In a non-interactive session (Rscript, Rmd render, CI) there is no terminal to answer, so loading the package fails or wedges inside library(epidatr) — a session-crash path under a documented configuration. I think .onLoad should not prompt at all: create the directory silently (with a message) or disable caching with a startup message.

Evidence (dev tip 87b10e1; identical on main)

R/epidatr-package.R:22-24:

if (cache_environ$use_cache) {
  set_cache(startup = TRUE)
}

set_cache()'s confirm defaults to TRUE (R/cache.R:106-113; the @param confirm doc even says it "should only be set in non-interactive scripts"), and the prompt lives at R/cache.R:146-168:

if (confirm) {
  user_input <- readline(glue::glue(
    "there is no directory at {cache_dir}; the cache will be turned off until a ",
    "viable directory has been set. Create one? (yes|no(default)) "
  ))
  ...

Maintainer-runnable repro

EPIDATR_USE_CACHE=TRUE EPIDATR_CACHE_DIR=/nonexistent Rscript -e 'library(epidatr)'

In a non-interactive session the readline() prompt has no usable stdin, so package load aborts (the exact failure mode varies by R version — readline() errors, or reads EOF and the prompt loop then fails on the empty input). The package never loads either way, which is the bug.

Expected vs. actual

• Expected: a missing cache directory at load time degrades gracefully — cache is created (non-interactively) or disabled with a packageStartupMessage; library(epidatr) always succeeds.
• Actual: library() itself fails in Rscript/Rmd/render pipelines — the environments where .Renviron-configured caches are most commonly used.

Suggested fix

Either:

1. Pass confirm = FALSE at startup — set_cache(startup = TRUE, confirm = FALSE) — so the directory is created without prompting and any failure degrades to "cache disabled" with a message; or
2. Gate the prompt on interactive() inside set_cache() (non-interactive → skip prompting, disable with a message).

Optionally also document in ?set_cache that startup never prompts.

I checked for prior reports (open/closed issues about EPIDATR_USE_CACHE, startup, or non-interactive failures — #193/#198 are about cache notifications/env-var docs) and found none covering this.