Version 4.0.0

This release introduces changes to error handling.

Previously, the parameter of the rejected promise callback was both the dispatched action and an Error object. The middleware also always constructed a new Error object, which caused unexpected mutation and circular references.

Now, the parameter of the rejected promise callback is the value of reject. The middleware does not construct a new error; it is your responsibility to make sure the promise is rejected with an Error object.

// before
const bar = () => ({
  type: 'FOO',
  payload: new Promise(() => {
    reject('foo');
  })
});.then(() => null, ({ reason, action }) => {
  console.log(action.type): // => 'FOO'
  console.log(reason.message); // => 'foo'
});

// after
const bar = () => ({
  type: 'FOO',
  payload: new Promise(() => {

    /**
     * Make sure the promise is rejected with an error. You
     * can also use `reject(new Error('foo'));`. It's a best
     * practice to reject a promise with an Error object.
     */
    throw new Error('foo');
  })
});.then(() => null, error => {
  console.log(error instanceof Error); // => true
  console.log(error.message); // => 'foo'
});