ResponderEventPlugin regression in React 15.4.0

[necolas]

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

Report a bug.

What is the current behavior?

The ResponderEventPlugin no longer recognizes start DOM events.

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/reactjs/69z2wepo/).

The EventPluginUtils.isStartish helper only checks for mouse/touch start events. In this section of code, the topLevelType used to be only topMouseDown or topTouchStart in React 15.3, but is now topClick in React 15.4.0. This means the event plugin can no longer recognize start events.

This PR exposes the issue in react-native-web, which uses the ResponderEventPlugin: necolas/react-native-web#255

What is the expected behavior?

The same behaviour as exhibited with React 15.3.2.

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

Works in React 15.3.2. Doesn't work in React 15.4.0.

[sophiebits]

If you add a React DOM node to your tree with onMouseDown={function() {}}, does that affect the behavior?

[necolas]

Yes it does! It appears that all the Touchable and PanResponder examples work (mouse and touch) if the page also includes:

<div
  onMouseDown={()=>{}}
  onMouseMove={()=>{}}
  onMouseUp={()=>{}}
  onTouchStart={()=>{}}
  onTouchMove={()=>{}}
  onTouchEnd={()=>{}}
/>

[remon-nashid]

I'm wondering how can we move this forward. Any directions to help a capable developer try to submit a pull request?

[gaearon]

If you're looking for an intro to the event system, this might be helpful. https://www.youtube.com/watch?v=dRo_egw7tBc

[sophiebits]

We need to add dependencies to these event types:

react/src/renderers/shared/shared/event/eventPlugins/ResponderEventPlugin.js

Line 59 in 0f34bdc

var eventTypes = {

It is tricky though because the plugin is shared between web and native and they have different event names. It may work to just always include the mouse events but I'm not sure if that causes problems in RN.

[necolas]

Which dependencies exactly? I've set mouse dependencies in RNW but that stopped working with React@15.4 - https://github.com/necolas/react-native-web/blob/f8f28980957ecb46393981d9b4bdfc820da06c26/src/modules/injectResponderEventPlugin.js

[sophiebits]

Oh, I would have thought that works. This code should run for your responder event handler and cause those deps to be listened to:

https://github.com/facebook/react/blob/v15.4.0/src/renderers/dom/shared/ReactDOMComponent.js#L221

[necolas]

The problem was that the EventConstants module no longer exports a key mirror – all the event type values are now null after this patch. Resolved the issue in RNW here: necolas/react-native-web@44ecbc0#diff-fecd5b3cfaeb4f62d70f4219e850f039