api.InputEvent.InputEvent - Safari 14.1.2 does not support initData in InputEvent constructor correctly

[ZhangYiJiang]

Browser: Safari 14.1.2
OS: macOS Catalina 10.15.7

What information was incorrect, unhelpful, or incomplete?

InputEvent() constructor's compatibility chart suggests Safari is fully compliant, but it does not correctly support initData. This makes it difficult to use InputEvent constructor since the properties defined in initData are immutable (readonly) on the actual event object, which means the constructor cannot be used.

What did you expect to see?

A note warning about Safari not supporting initData correctly

Did you test this? If so, how?

Webkit bug tracker: https://bugs.webkit.org/show_bug.cgi?id=170416

In Safari's console -

> e = new InputEvent('beforeinput', { inputType: 'insertText' }) 
< InputEvent {isTrusted: false, inputType: "", data: null, dataTransfer: null, getTargetRanges: function, …}
> e.inputType
< ""

Compared to in Firefox

> e = new InputEvent('beforeinput', { inputType: 'insertText' })
< beforeinput { target: null, isTrusted: false, isComposing: false, inputType: "insertText", detail: 0, layerX: 0, layerY: 0, which: 0, rangeOffset: 0, SCROLL_PAGE_UP: -32768, … }
> e.inputType
< "insertText"

MDN page report details

• Query: api.InputEvent.InputEvent
• MDN URL: https://developer.mozilla.org/en-US/docs/Web/API/InputEvent/InputEvent
• Report started: 2021-08-13T16:21:29.960Z

[gsnedders]

#7287 is relevant here; WebKit has:

dictionary InputEventInit : UIEventInit {
    DOMString? data = null;
};

As such the rest of the dictionary is unsupported.