Inconsistent crossbrowser onBeforeInput paste event behavior

[johtso]

React version: 17.0.2

In Chrome, pasting triggers onPaste and onBeforeInput, with the nativeEvents ClipboardEvent and TextEvent respectively.

In Firefox, pasting only triggers onPaste with nativeEvent paste.

If I'm not mistaken, this seems to be the code responsible for not triggering onBeforeInput on native paste events:

react/packages/react-dom/src/events/plugins/BeforeInputEventPlugin.js

Lines 328 to 331 in 27c9c95

	case 'paste':
	// If a paste event occurs after a keypress, throw out the input
	// chars. Paste events should not lead to BeforeInput events.
	return null;

React version: 17.0.2 and 18.0.0

17.0.2
https://codesandbox.io/s/condescending-cerf-e1qt9?file=/src/App.js
18.0.0
https://codesandbox.io/s/sparkling-sun-fylti?file=/src/App.js

[eps1lon]

Thanks for the report.

The behavior is the same, except in chrome pasting triggers both onPaste and onBeforeInput rather than just onPaste

This is also the behavior in React 17 for me.

On the other hand with Firefox, pasting seems to never cause onBeforeInput to be called.

This sounds like a bug to me considering firefox does dispatch an beforeinput native event: https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/beforeinput_event#simple_logger

[johtso]

The behavior is the same, except in chrome pasting triggers both onPaste and onBeforeInput rather than just onPaste

This is also the behavior in React 17 for me.

You're right! Well that simplifies things if nothing's changed in 18. Updated my initial description.

From the code comments it seems like the intention is for pasting to not trigger onBeforeInput?

react/packages/react-dom/src/events/plugins/BeforeInputEventPlugin.js

Lines 328 to 331 in 27c9c95

	case 'paste':
	// If a paste event occurs after a keypress, throw out the input
	// chars. Paste events should not lead to BeforeInput events.
	return null;

[eps1lon]

Huh. Especially the following sentence is odd:

react/packages/react-dom/src/events/plugins/BeforeInputEventPlugin.js

Line 330 in 27c9c95

// chars. Paste events should not lead to BeforeInput events.

I'm not sure where they took the "should" from because that's not following current browser implementations. Would be nice to find out what the purpose of this change was.

Though I think this particular issue is already tracked in #11211 because in FireFox onBeforeInput would trigger if the native event would be used.