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ResultError

Overview​

The ResultError class is a specialized error type in the @ts-rust/std library, used with the Result type to represent errors that occur during operations that can succeed or fail. It extends the AnyError class where template T is ResultErrorKind and provides additional context about why a Result operation failed, including an associated ResultErrorKind.

When It Appears​

ResultError is used in scenarios involving the Result type, such as:

  • Returning an Err variant from a Result when an operation fails unexpectedly (see CheckedError for more details).
  • Throwing an error when attempting to unwrap an Err value using methods like unwrap() or expect().

Usage​

ResultError is encountered when working with the Result type and its methods. It allows developers to handle failure cases explicitly and provides details about the error through its kind property.

Example​

import { err, Result, ResultErrorKind, isResultError } from "@ts-rust/std";

// Create a Result with unexpected error
const result: Result<number, string> = ok(0).map(() => {
  throw new Error("oops");
});

if (result.isErr()) {
  const error = result.unwrapErr();

  if (error.isUnexpected()) {
    console.log(error.unexpected.message); // "[PredicateException] `map`: callback `f` threw an exception. Reason: Error: oops"
    console.log(error.unexpected.kind); // "PredicateException"
  }
}

// Using unwrap() on an Err value
try {
  result.unwrap();
} catch (e) {
  if (isResultError(e)) {
    console.log(e.message); // "[UnwrapCalledOnErr] `unwrap`: called on `Err`."
    console.log(e.kind); // [UnwrapCalledOnErr]
    console.log(e.reason); // "Error: UnwrapCalledOnErr ...."
  }
}

See Also​