Assert a custom condition

assert_custom() builds an assertion from your own condition. It is assert_output() or suggest_output(), chosen by type.

Usage

assert_custom(condition, message, field = NULL, type = c("assert", "suggest"))

Arguments

condition

A function, or a formula using .x, that takes the output (or the field) and returns TRUE or FALSE.

message

The message shown when the check fails, which with_assertions() also sends back to the model on a retry.

field

The output field passed to condition. With NULL (the default), the whole output (a named list) is passed.

type

"assert" (the default) for a hard assertion, which makes with_assertions() retry when it fails, or "suggest" for a soft one, which only gives a warning.

Value

An assertion for assertion_set() or with_assertions().

See also

Other assertions: assert_contains(), assert_length(), assert_matches(), assert_not_contains(), assert_not_empty(), assert_not_matches(), assert_one_of(), assert_range(), assertions, with_assertions()

Examples

# Exactly three sentences
assert_custom(
  ~ lengths(regmatches(.x$answer, gregexpr("[.!?]", .x$answer))) == 3,
  "Answer in exactly three sentences"
)
#> 
#> ── Hard Assertion 
#> • Field: any field
#> • Message: "Answer in exactly three sentences"

# Compare two output fields
assert_custom(
  function(x) nchar(x$summary) < nchar(x$details),
  "The summary must be shorter than the details"
)
#> 
#> ── Hard Assertion 
#> • Field: any field
#> • Message: "The summary must be shorter than the details"