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{ lib }:
rec {
/* Throw if pred is false, else return pred.
Intended to be used to augment asserts with helpful error messages.
Example:
assertMsg false "nope"
stderr> error: nope
assert assertMsg ("foo" == "bar") "foo is not bar, silly"; ""
stderr> error: foo is not bar, silly
Type:
assertMsg :: Bool -> String -> Bool
*/
# TODO(Profpatsch): add tests that check stderr
assertMsg =
# Predicate that needs to succeed, otherwise `msg` is thrown
pred:
# Message to throw in case `pred` fails
msg:
pred || builtins.throw msg;
/* Specialized `assertMsg` for checking if `val` is one of the elements
of the list `xs`. Useful for checking enums.
Example:
let sslLibrary = "libressl";
in assertOneOf "sslLibrary" sslLibrary [ "openssl" "bearssl" ]
stderr> error: sslLibrary must be one of [
stderr> "openssl"
stderr> "bearssl"
stderr> ], but is: "libressl"
Type:
assertOneOf :: String -> ComparableVal -> List ComparableVal -> Bool
*/
assertOneOf =
# The name of the variable the user entered `val` into, for inclusion in the error message
name:
# The value of what the user provided, to be compared against the values in `xs`
val:
# The list of valid values
xs:
assertMsg
(lib.elem val xs)
"${name} must be one of ${
lib.generators.toPretty {} xs}, but is: ${
lib.generators.toPretty {} val}";
}
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