unicorn/no-useless-fallback-in-spread

Spreading undefined or null into an object literal adds nothing and doesn't throw. So { ...(options || {}) } and { ...(options ?? {}) } give the same object as { ...options }.

This is only true for objects. Spreading undefined into an array or a call's arguments throws, so [...(items || [])] isn't reported.

--fix removes the fallback.

Configure

Off by default. To turn it on:

[lint.rules]
"unicorn/no-useless-fallback-in-spread" = "error" # or "warn"

Examples

Reported:

function request(url, options, extraHeaders) {
  const headers = { accept: "application/json", ...(extraHeaders || {}) };
  return fetch(url, { ...(options ?? {}), headers });
}

Not reported:

function request(url, options, extraHeaders) {
  const headers = { accept: "application/json", ...extraHeaders };
  return fetch(url, { ...options, headers });
}

// the fallback has something in it
const settings = { ...(saved || { theme: "light" }) };

// arrays need the fallback
const all = [...(items || [])];