Illustration on using `vetr` with `date_between`

datebw-vetr.R

date.2 <- rep(Sys.Date(), 2) # length 2 date object
date.1 <- date.2[1]
valid_identifier_regex <- function() "^\\w+$"

date_between <- function(column_name, date_range) {
  vetr(
    character(1L) && grepl(valid_identifier_regex(), .),
    (date.2 || date.1) && !anyNA(.)
  )
  TRUE
}
dates.good <- as.Date(c('2017-07-01', '2017-08-01'))
dates.bad.2 <- as.POSIXct(c('2017-07-01', '2017-08-01'))
dates.bad.3 <- rep(dates.good, 2)

date_between('thiscol', dates.good)
## [1] TRUE
date_between('this col', dates.good)
## Error in date_between(column_name = "this col", date_range = dates.good) :
##   For argument `column_name`, `grepl(valid_identifier_regex(), "this col")` is not TRUE (FALSE)
date_between('thiscol', dates.bad.2)
## Error in date_between(column_name = "thiscol", date_range = dates.bad.2) :
##   For argument `date_range`, `class(dates.bad.2)[2]` should be "Date" (is "POSIXt")
date_between('thiscol', dates.bad.3)
## Error in date_between(column_name = "thiscol", date_range = dates.bad.3) :
##   For argument `date_range`, `dates.bad.3` should be length 1, or length 2 (is 4)