unicorn/no-useless-promise-resolve-reject

An async function wraps whatever it returns in a promise, and turns anything it throws into a rejection. Callbacks passed to .then(), .catch() and .finally() work the same way. Returning Promise.resolve(value) or Promise.reject(error) from them wraps a second time for nothing. return value and throw error do the same thing.

yield Promise.resolve(value) in an async generator is reported too.

--fix rewrites to return value or throw error. It doesn't touch a Promise.reject() inside a try, because that try would catch the throw.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"unicorn/no-useless-promise-resolve-reject" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"unicorn/no-useless-promise-resolve-reject" = ["error", {
  allowReject = false,
}]

Examples#

example.js3 problems

async function findUser(id) {
  if (!id) {
    return Promise.reject(new Error("missing id"));
  }
  return Promise.resolve(cache.get(id));
}

fetchUser().then(user => Promise.resolve(user.name));

example.js1 problem

async function* pages() {
  yield Promise.resolve(firstPage);
}

example.jsNo problems

async function findUser(id) {
  if (!id) {
    throw new Error("missing id");
  }
  return cache.get(id);
}

fetchUser().then(user => user.name);

// not async: the caller needs the promise
function findCached(id) {
  return Promise.resolve(cache.get(id));
}

Options#

Option	Default	What it does
`allowReject`	`false`	Allow `Promise.reject()`. `Promise.resolve()` is still reported.

example.jswith { "allowReject": true }No problems

async function findUser(id) {
  return Promise.reject(new Error("not found"));
}