The implementation of `isTRUE` has been changed in R-3.5.0 from
identical(x, TRUE) to is.logical(x) && length(x) == 1L && !is.na(x) && x.
This backport overloads the old implementation for R versions prior to 3.5.0.
# get function from namespace instead of possibly getting# implementation shipped with recent R versions:bp_isTRUE = getFromNamespace("isTRUE", "backports")
bp_isTRUE(FALSE)
bp_isTRUE(iris)