this shows the correct way to suppress warnings is suppressWarnings() instead of options(warn = -1) alone; similarly, you should use suppressMessages() to suppress messages

warnings.R

options(warn = -1)
# cannot really suppress warnings from the root level
withCallingHandlers(warning("hi"), warning = function(w) {
    print(w)
})
# the warning can still be captured:

## <simpleWarning in withCallingHandlers(warning("hi"), warning = function(w) {    print(w)}): hi>

# however, this always works
withCallingHandlers(suppressWarnings(warning("hi")), warning = function(w) {
    print(w)
})

# even if when warn=0
options(warn = 0)
withCallingHandlers(suppressWarnings(warning("hi")), warning = function(w) {
    print(w)
})