This library provides an easy to use Error type for idiomatic error handling in Motoko applications.
[dependencies]
snafu = "0.1.1"Use Snafu.Result<T> as the return type for functions that can fail.
import Snafu "mo:snafu/Snafu";
func registerUsername(name : Text) : Snafu.Result<Nat> {
if (name == "") {
return Snafu.snafu("Invalid empty name")
};
if (users.contains(name)) {
return Snafu.snafu("Name already taken")
};
users.add(name);
return #ok(users.size());
};Add additional context to existing errors, to make it easier to troubleshoot when things go wrong.
let userId = registerUsername("") |> (switch _ {
case (#ok ok) ok;
case (#err err)
return Snafu.context(err, "Failed to create User")
});
...Before returning from an Actor pretty print the error, choosing the right level of detail.
import Snafu "mo:snafu/Snafu";
import Result "mo:base/Result";
actor {
func registerUser() async Result.Result<UserId, Text> {
register() |> Snafu.pretty()
// #err("Failed to create User")
register() |> Snafu.prettyTrace()
// #err(
// "Error: Failed to create User
// Caused by:
// Invalid empty name
// ")
}
}Check out test/Example.mo for a slightly more involved example.
Lots of inspiration for this library was taken from using the anyhow Rust crate.