catch-or-return.md

Enforces the use of catch() on un-returned promises (catch-or-return)

Ensure that each time a then() is applied to a promise, a catch() is applied as well. Exceptions are made if you are returning that promise.

Valid

myPromise.then(doSomething).catch(errors)
myPromise
  .then(doSomething)
  .then(doSomethingElse)
  .catch(errors)
function doSomethingElse() {
  return myPromise.then(doSomething)
}

Invalid

myPromise.then(doSomething)
myPromise.then(doSomething, catchErrors) // catch() may be a little better
function doSomethingElse() {
  return myPromise.then(doSomething)
}

Options

allowThen

You can pass an { allowThen: true } as an option to this rule to allow for .then(null, fn) to be used instead of catch() at the end of the promise chain.

allowFinally

You can pass an { allowFinally: true } as an option to this rule to allow for .finally(fn) to be used after catch() at the end of the promise chain. This is different from adding 'finally' as a terminationMethod because it will still require the Promise chain to be "caught" beforehand.

terminationMethod

You can pass a { terminationMethod: 'done' } as an option to this rule to require done() instead of catch() at the end of the promise chain. This is useful for many non-standard Promise implementations.

You can also pass an array of methods such as { terminationMethod: ['catch', 'asCallback', 'finally'] }.

This will allow any of

Promise.resolve(1)
  .then(() => {
    throw new Error('oops')
  })
  .catch(logerror)
Promise.resolve(1)
  .then(() => {
    throw new Error('oops')
  })
  .asCallback(cb)
Promise.resolve(1)
  .then(() => {
    throw new Error('oops')
  })
  .finally(cleanUp)