react: react-test-renderer/shallow setState callback is never called

Do you want to request a feature or report a bug?

Bug, following on from https://github.com/airbnb/enzyme/issues/953

What is the current behavior?

In node_modules/react-test-renderer/cjs/react-test-renderer-shallow.development.js, the callback second argument to setState is never called.

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://jsfiddle.net or similar (template: https://jsfiddle.net/84v837e9/).

import ShallowRenderer from 'react-test-renderer/shallow'

const renderer = new ShallowRenderer()
renderer.render(<YourComponent />)
const instance = renderer.getMountedInstance()
instance.methodThatCallsSetState()
// => callback passed into setState as the second argument within methodThatCallsSetState is never called

The shallow renderer code is as follows:

Updater.prototype.enqueueSetState = function enqueueSetState(publicInstance, partialState, callback, callerName) {
  if (typeof partialState === 'function') {
    partialState = partialState(publicInstance.state, publicInstance.props);
  }

  this._renderer._newState = _extends({}, publicInstance.state, partialState);

  this._renderer.render(this._renderer._element, this._renderer._context);
};

As you can see, the callback is ignored. In the deep renderer (node_modules/react-test-renderer/cjs/react-test-renderer.development.js), the callback is used:

enqueueSetState: function (instance, partialState, callback) {
  var fiber = ReactInstanceMap_1.get(instance);
  var priorityLevel = getPriorityContext(fiber, false);
  callback = callback === undefined ? null : callback;
  {
    warnOnInvalidCallback(callback, 'setState');
  }
  addUpdate$1(fiber, partialState, callback, priorityLevel);
  scheduleUpdate(fiber, priorityLevel);
}

What is the expected behavior?

The callback is called.

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?

React v16, react-test-renderer v16. I don’t know if this worked before.