`validate::variables` returns R variables that are not columns of data

[edwindj]

validate::variables returns R variables that are not columns data to be checked.

library(validate)
rules <- validator(A %in% letter[1:2])
variables(rules)

## [1] "A"      "letter"

[edwindj]

The following statement returns all variables mentioned in the rule set. For many purposes it is nicer that the function only returns the columns of the data to be checked (i.e. "x")

library(validate)

rules <- validator(x > ref$y)
variables(rules)

## [1] "x"   "ref" "y"