Result Type

Discriminated result for success or error operations, with optional metrics

Overview

The library functions return a result that avoids exceptions and facilitates flow control.

• run returns an object with ok: true and data, or ok: false and error.
• all returns an array with results per task: ok, error or skipped.
• Optional metrics help observe attempts, retries, and duration.

RunResult in run

import { run } from "tryo";

type User = { id: string; name: string };

const result = await run<User>(() => fetch("/api/user").then((r) => r.json()));

if (result.ok) {
  console.log(result.data);
} else {
  console.error(result.error.code);
}

Result structure:

• Success: { ok: true, data, error: null, metrics? }
• Error: { ok: false, data: null, error, metrics? }

Metrics include:

• totalAttempts
• totalRetries
• totalDuration
• lastError?

RunAllItemResult in all

import { all } from "tryo";

const tasks = [
  () => fetch("/a").then((r) => r.text()),
  () => fetch("/b").then((r) => r.text()),
  () => fetch("/c").then((r) => r.text()),
];

const results = await all<string>(tasks);

for (const r of results) {
  if (r.status === "ok") console.log(r.data);
  if (r.status === "error") console.error(r.error.code);
}

Possible states per item:

• ok: successful task with data
• error: failed task with error
• skipped: task not rund due to cancellation or fail-fast

Type helpers for all

The library exports utilities to discriminate results and improve typing:

import { isSuccess, type SuccessResult, type ErrorResult } from "tryo";

const results = await all<number>([
  async () => 1,
  async () => {
    throw new Error("x");
  },
]);

const successes: SuccessResult<number>[] = results.filter(isSuccess);
const failures: ErrorResult<any>[] = results.filter(
  (r) => r.status === "error"
);