CHAN.RUN

tryAsync

tryAsync()

Call Signature

function tryAsync<TArgs, T, TErrors>(fn, ...args): Promise<AsyncResult<T, InferFaultErrors<TErrors>>>;

Defined in: src/try.ts

Run async code, return a discriminated result — never rejects.

Pass a declared function directly to get typed errors:

const getUser = declares([NotFoundError], async (id: string) => fetchUser(id));
const result = await tryAsync(getUser, "123");
// result.error is NotFoundError, not unknown

Or wrap any expression in a lambda:

const result = await tryAsync(() => fetchUser(id));
// result.error is unknown

Type Parameters

Type Parameter
`TArgs` extends `unknown`[]
`T`
`TErrors` extends `NamedFaultErrorClass`<`string`>[]

Parameters

Parameter	Type
`fn`	`DeclaredFn`<`TArgs`, `Promise`<`T`>, `TErrors`>
...`args`	`TArgs`

Returns

Promise<AsyncResult<T, InferFaultErrors<TErrors>>>

Examples

const result = await tryAsync(getUser, req.params.id);
if (!result.ok) {
  return match(result.error, [NotFoundError, DbError], {
    NotFoundError: (e) => res.status(404).json({ error: e.message }),
    DbError: () => res.status(503).json({ error: "Service unavailable" }),
  });
}
res.json(result.data);

const result = await tryAsync(() => fetch("https://api.example.com/data"));
if (!result.ok) {
  logger.error("API request failed", { error: result.error });
  return fallbackData;
}
const data = await result.data.json();

async function UserPage({ id }: { id: string }) {
  const result = await tryAsync(getUser, id);
  if (!result.ok) return <ErrorCard error={result.error} />;
  return <UserProfile user={result.data} />;
}

async function onSubmit(values: FormValues) {
  const result = await tryAsync(() => api.post("/signup", values));
  if (!result.ok) {
    match(result.error, {
      ValidationError: (e) => setFieldErrors(e.message),
      _: () => toast.error("Something went wrong"),
    });
    return;
  }
  router.push("/dashboard");
}

import { readFile } from "node:fs/promises";

const result = await tryAsync(() => readFile("./data.json", "utf-8"));
if (!result.ok) {
  console.error("Could not read file:", result.error);
  process.exit(1);
}
const config = JSON.parse(result.data);

Call Signature

function tryAsync<T>(fn): Promise<AsyncResult<T>>;

Defined in: src/try.ts

Run async code, return a discriminated result — never rejects.

Pass a declared function directly to get typed errors:

const getUser = declares([NotFoundError], async (id: string) => fetchUser(id));
const result = await tryAsync(getUser, "123");
// result.error is NotFoundError, not unknown

Or wrap any expression in a lambda:

const result = await tryAsync(() => fetchUser(id));
// result.error is unknown

Type Parameters

Type Parameter
`T`

Parameters

Parameter	Type
`fn`	() => `Promise`<`T`>

Returns

Promise<AsyncResult<T>>

Examples

const result = await tryAsync(getUser, req.params.id);
if (!result.ok) {
  return match(result.error, [NotFoundError, DbError], {
    NotFoundError: (e) => res.status(404).json({ error: e.message }),
    DbError: () => res.status(503).json({ error: "Service unavailable" }),
  });
}
res.json(result.data);

const result = await tryAsync(() => fetch("https://api.example.com/data"));
if (!result.ok) {
  logger.error("API request failed", { error: result.error });
  return fallbackData;
}
const data = await result.data.json();

async function UserPage({ id }: { id: string }) {
  const result = await tryAsync(getUser, id);
  if (!result.ok) return <ErrorCard error={result.error} />;
  return <UserProfile user={result.data} />;
}

async function onSubmit(values: FormValues) {
  const result = await tryAsync(() => api.post("/signup", values));
  if (!result.ok) {
    match(result.error, {
      ValidationError: (e) => setFieldErrors(e.message),
      _: () => toast.error("Something went wrong"),
    });
    return;
  }
  router.push("/dashboard");
}

import { readFile } from "node:fs/promises";

const result = await tryAsync(() => readFile("./data.json", "utf-8"));
if (!result.ok) {
  console.error("Could not read file:", result.error);
  process.exit(1);
}
const config = JSON.parse(result.data);