Check that an argument is a spec of an accepted role

Composition errors are worth catching in R, where the argument can be named, rather than in Julia, where the error arrives from inside a constructor. A julia() expression with no role is accepted for any role, since the caller has said what it is by writing the code.

Usage

assert_role(
  x,
  roles,
  null_ok = FALSE,
  arg_name = deparse(substitute(x)),
  labels = NULL
)

Arguments

x

Object to check.

roles

Character vector of accepted roles.

null_ok

Logical. Whether NULL is accepted.

arg_name

Name used in error messages.

labels

Optional named character vector describing each role, used in the error message, for instance c(prior = "a prior (e.g. Normal())"). Roles without an entry are described by their own name.

Value

Invisibly TRUE.

Examples

transform <- julia_spec("LogTransform", .role = "transform")
assert_role(transform, "transform")
try(assert_role(transform, "model"))
#> Error : `transform` must be a model spec.