promise/catch-or-return

When a promise chain is a statement by itself, no other code can handle its errors. Without a catch() at the end, a failure becomes an unhandled rejection.

The rule checks statements that call then(), catch(), finally() or a static method such as Promise.all(). A chain that's returned, awaited or assigned isn't reported, because the code that receives it can handle the error. Cypress chains that start with cy. aren't reported either.

Configure

Off by default. To turn it on:

[lint.rules]
"promise/catch-or-return" = "error" # or "warn"

Every option, set to its default:

[lint.rules]
"promise/catch-or-return" = ["error", {
  allowFinally = false,
  allowThen = false,
  allowThenStrict = false,
  terminationMethod = "catch",
}]

Examples

Reported:

function refresh() {
  loadItems().then(render);
}

Not reported:

function refresh() {
  loadItems().then(render).catch(showError);
}

function refreshLater() {
  return loadItems().then(render);
}

async function refreshNow() {
  await loadItems().then(render);
}

cy.get("button").then(click);

Options

Option	Default	What it does
allowFinally	false	Allow finally() after the catch().
allowThen	false	Allow then(a, b) with two arguments as the end of a chain.
allowThenStrict	false	Allow then(null, b) as the end of a chain.
terminationMethod	"catch"	The method, or a list of methods, that a chain must end with.

By default, the catch() must come last, so this is reported:

loadItems().then(render).catch(showError).finally(hideSpinner);

loadItems().then(render).catch(showError).finally(hideSpinner);

loadItems().then(render, showError);

With allowThenStrict, the first argument must be null:

loadItems().then(render).then(null, showError);

loadItems().then(render, showError);

terminationMethod replaces catch. List "catch" too if you want to keep it:

loadItems().then(render).done();
loadItems().then(render).catch(showError);

loadItems().then(render).catch(showError);