`check_dots_used()` can give a false positive due to lazy evaluation

[jennybc]

Motivated by r-lib/devtools#2672. In the matching PR, OP adds debug = as a formal argument to devtools::load_all(), even though devtools::load_all() explicitly has ... for the purpose of passing extra arguments along to pkgload::load_all().

https://github.com/r-lib/devtools/blob/ab097cc996b0e9e1fd067a95a71b28054a5b8a7c/R/pkgload.R#L2

https://github.com/r-lib/devtools/blob/ab097cc996b0e9e1fd067a95a71b28054a5b8a7c/R/pkgload.R#L26-L36

The problem is, even though debug is a formal argument of pkgload::load_all(), the most-commonly executed code paths don't actually evaluate debug and, therefore, rlang::check_dots_used() raises a false warning or error. This happens whenever there's no need to compile code, which is most of the time:

https://github.com/r-lib/pkgload/blob/ce84bbe18c56952da73d36c9cccc19820916919e/R/load.R#L178

The warning suggests that there's no match with formal arguments ("Did you misspell an argument name?"), but that's not the problem.

Here's a reprex.

inner <- function(x, debug = TRUE) {
  if (x > 0) {
    message("debugging is ", if (debug) "on" else "off")
  }
  x
}

outer <- function(x, ...) {
  rlang::check_dots_used(action = rlang::warn)
  result <- inner(x, ...)
  message("inner() completed successfully with result: ", result)
  result
}

# No warning: inner() evaluates `debug`
outer(1, debug = FALSE)
#> debugging is off
#> inner() completed successfully with result: 1
#> [1] 1

# False warning: inner() still runs fine, it just doesn't happen to
# evaluate `debug` in this code path
outer(-1, debug = FALSE)
#> inner() completed successfully with result: -1
#> Warning in outer(-1, debug = FALSE): Arguments in `...` must be used.
#> ✖ Problematic argument:
#> • debug = FALSE
#> ℹ Did you misspell an argument name?
#> [1] -1

^{Created on 2026-02-25 with reprex v2.1.1.9000}