Adventures with `ensurer`

check-groceries.R

library(ensurer) # awesome

# Example 1 --- OK
groceries <- c("eggs", "bread", "milk")
check_that(groceries, "bread" %in% .)

# Example 2 --- :-(
# I'd really like this to work! It's quite readable.
# Doesn't work b/c `ensurer` (v1.1) doesn't first evaluate calls.
contains <- function (what) function (x) { what %in% x }
check_that(groceries, contains("bread")) # :-(

# Example 3 --- ??
# On the other hand, this will wwork. `contains_bread` is not a call.
contains_bread <- contains("bread")
check_that(groceries, contains_bread)

# Example 4 --- what I want for production: have upstream data changed?
has_md5 <- function (expected) {
  function (obj) {
    identical(expected, digest::digest(obj, "md5"))
  }
}
check_that(groceries, has_md5("ad2a7a75b9443b916224dc7cf347e8ac"))
# ... perform analysis of groceries

# Example 6 --- thanks to @stefanbache
ensure_md5 <- function (object, expected) {
  ensure_that(object, identical(md5(.), expected))
}

ensure_md5(groceries, "ad2a7a75b9443b916224dc7cf347e8ac")