makeSimpleAsync, perform and their problems

[tomhoule]

We pretty much decided we were not going to go forward with makeSimpleAsync because it's too inflexible and does not compose well with other sagas.

The other idea was perform, which is a very basic saga that just dispatches the _SUCCESS or _FAILURE action and uses an optional error handler.

The problem is that perform has to signal the success or error to the parent saga, which can be done with an exception:

try {
  const response = yield perform(call(api.books, action.payload), action)
  ...do something
} catch (_) { }

or with a value

const response = yield perform(call(api.books, action.payload), action)
if (response) {
  ...do something
}

Both methods are ugly and more verbose than they need to be. What we could do instead is wrap the parent saga in another one that dispatches the _SUCCESS and _FAILURE action and handle errors.

The only responsibility of the child saga is then to signal the result by returning a success value or throwing an error.

[fnune]

And that parent saga would be a wrapped re-export of takeLatest, takeEvery, etc. right?

[tomhoule]

We can provide these as helpers but you can use that saga by itself.

[tomhoule]

Something like:

export function buckle(saga, onError) {
  return function* inner(action) {
  const success = action.meta.success || `${action.type}_SUCCESS`
  const failure = action.meta.failure || `${action.type}_FAILURE`
  try {
    const result = yield call(saga, action)
    yield put({ type: success, payload: result })
  } catch (err) {
    yield call(onError, failure, err)
  }
}