queryCommandSupported('paste') clarification for Chrome

[RobertBColton]

Building an HTML5 application with clipboard support, I intended to use queryCommandSupported to disable cut, copy, and paste buttons if they were not supported. This worked fine in all browsers except for Chrome, which always returns true for all 3 commands, even if they are not "supported."

In Chrome 61, even though queryCommandSupported('paste') returns true, document.execCommand('paste') will always return false and do nothing. It does execute the paste command if executed from a Chrome extension though.

I reported this to the Chrome dev team and they would like some clarification because they feel the spec is ambiguous.
https://bugs.chromium.org/p/chromium/issues/detail?id=757140#c4

Could someone please clarify whether Chrome is doing what the spec intends by returning true at all times from queryCommandSupported('paste')?

[rniwa]

This is just a bug in Chrome's implementation. Since Chrome doesn't allow execCommand('paste'), it should just return false in queryCommandSupported('paste'). Maybe it supports when the webpage is "installed" or something? But if that's the case, it should continue to return false until the web app is installed.

[johanneswilm]

We did discuss this at the meeting today:

RESOLUTION: Spec should say that supported should be false if you are in an environment where you are always going to fail. [1]

[1] https://www.w3.org/2017/09/05-editing-minutes.html

[johanneswilm]

@yosinch Please reopen if it still does not seem clear.

[yosinch]

Thanks Johannes. The statement is clear for me.
It is nice that the "paste" section has a condition when queryCommandSupported() return false.