API reference › @evolu/common › Result › tryAsync

Call Signature

function tryAsync<T>(
  promiseThunk: Thunk<Awaitable<T>>,
): Promise<Result<T, unknown>>;

Defined in: packages/common/src/Result.ts:703

Wraps an async function that may throw or reject, returning a Result.

When provided, mapError converts the caught unknown value into a typed domain error.

Some async APIs throw or reject for both recoverable and unrecoverable errors. In that case, convert only the errors the caller can recover from and rethrow the rest. The tryAsync error mapper leaves rethrown values as Promise rejections instead of converting them to Err.

Example

import {
  assert,
  assertErr,
  assertEqual,
  assertOk,
  assertType,
  tryAsync,
  type Result,
  type Typed,
} from "@evolu/common";

class LegacySeatUnavailableError extends Error {}

const legacyReserveSeat = (seat: string): Promise<void> => {
  if (seat === "A1") {
    return Promise.reject(new LegacySeatUnavailableError());
  }
  if (seat === "B1") return Promise.reject(new Error("Database error"));
  return Promise.resolve();
};

const reserveSeat = (
  seat: string,
): Promise<Result<void, SeatUnavailableError>> =>
  tryAsync(
    () => legacyReserveSeat(seat),
    (error) => {
      if (error instanceof LegacySeatUnavailableError) {
        return { type: "SeatUnavailable", seat };
      }
      throw error;
    },
  );

interface SeatUnavailableError extends Typed<"SeatUnavailable"> {
  readonly seat: string;
}

const result = await reserveSeat("B2");
assertType<Result<void, SeatUnavailableError>, typeof result>();
assertOk(result, undefined);
assertErr(await reserveSeat("A1"), {
  type: "SeatUnavailable",
  seat: "A1",
});
const databaseError = await tryAsync(() => reserveSeat("B1"));
assertErr(databaseError);
assert(databaseError.error instanceof Error, "Expected an Error.");
assertEqual(databaseError.error.message, "Database error");

Call Signature

function tryAsync<T, E>(
  promiseThunk: Thunk<Awaitable<T>>,
  mapError: (error: unknown) => E,
): Promise<Result<T, E>>;

Defined in: packages/common/src/Result.ts:708

Maps thrown or rejected values to a typed error.

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