assert_engine: Throws an error if a condition isn't met

In assertive.base: A Lightweight Core of the 'assertive' Package

Description

The workhorse of the package that creates an assertion from a predicate. If a condition isn't met, then an error is thrown. This function is exported for use by package developers so that they can create their own assert functions.

Usage

assert_engine(
  predicate,
  ...,
  msg = "The assertion failed.",
  what = c("all", "any"),
  na_ignore = FALSE,
  severity = c("stop", "warning", "message", "none")
)

Arguments

predicate	Function that returns a logical value (possibly a vector).
...	Passed to the predicate function.
msg	The error message, in the event of failure.
what	Either 'all' or 'any', to reduce vectorised tests to a single value.
na_ignore	A logical value. If FALSE, NA values cause an error; otherwise they do not. Like na.rm in many stats package functions, except that the position of the failing values does not change.
severity	How severe should the consequences of the assertion be? Either "stop", "warning", "message", or "none".

Value

FALSE with the attribute message, as provided in the input.

Note

Missing values are considered as FALSE for the purposes of whether or not an error is thrown.

Examples

# Basic usage is like do.call; pass a predicate and the arguments to it.
dont_stop(assert_engine(is_true, c(TRUE, FALSE, NA)))

# Customise the error message
dont_stop(
  assert_engine(is_true, c(TRUE, FALSE, NA), msg = "Not everything is true")
)

# Only fail when no values match the predicate's conditions
dont_stop(assert_engine(is_true, logical(3), what = "any"))

# You can use base predicates, but the error message isn't as informative
dont_stop(assert_engine(is.matrix, 1:5))

# Reduce the severity of failure
assert_engine(is_true, c(TRUE, FALSE, NA), severity = "message")

assertive.base documentation built on Feb. 8, 2021, 9:06 a.m.