Add commandfor & command attributes to HTMLButtonElement

[keithamus]

This adds the commandfor & command attributes and a "command" event using the CommandEvent interface.

Button activation checks if the button has a "commandfor" target and if so performs invoker command behaviour depending on command and the target element.

Some related (eventual) follow up issues around this feature:

• Investigate making the invalid state of <button type> _not_ submit #10462; Investigate making the invalid state of <button type> not submit

• Lift restriction on buttons with implicit type=submit and command/commandfor being no-op #10832; Lift restriction on buttons with implicit type=submit and command/commandfor being no-op

• At least two implementers are interested (and none opposed):

  • Mozilla Supportive & prototyping
  • Webkit
  • Chromium supportive; actively prototyping.

• Tests are written and can be reviewed and commented upon at:

  • Mark invokers tests as non-tentative web-platform-tests/wpt#42664 (PR to make the tests non-tentative)

• Implementation bugs are filed:

  • Chromium Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1490919
  • Chromium Patch: https://chromium-review.googlesource.com/c/chromium/src/+/4926471
  • Gecko Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1856430
  • Gecko Patch: https://phabricator.services.mozilla.com/D190449
  • WebKit Bug: https://bugs.webkit.org/show_bug.cgi?id=262840
  • Webkit Patch: Add invoketarget & invokeaction attributes WebKit/WebKit#18794

• MDN issue is filed: Add documentation for the "command" and "commandfor" attributes, and "command" event. mdn/content#30829

• The top of this comment includes a clear commit message to use.

• a11y & i18n are considered and relevant PRs are created: Add command & commandfor attribute related mappings w3c/aria#2354

(See WHATWG Working Mode: Changes for more details.)

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/dom.html ( diff )
/form-elements.html ( diff )
/index.html ( diff )
/indices.html ( diff )
/interaction.html ( diff )
/interactive-elements.html ( diff )
/webappapis.html ( diff )

[scottaohara]

I realize this is also in the steps for getting the popover target element, but in both cases I'm wondering why its specified to return null if the node is in the disable state?

Doing so, at least with <button popovertarget=foo disabled> testing in chrome, results in that element not exposing whether the popover is in the expanded or collapsed state - as I'm assuming due to

"If node is disabled, then return null."

that state gets removed. That's unexpected, to have that state removed based on whether the button is disabled or not. And for invokertarget - if it is really is going to do more than just show/hide content - there are a lot of other states that should still be exposed, regarless of if the element is in the disabled state or not.

edit: I can file a bug for disabled / popovertarget if necessary - i just wanted to get insight on this first, before I went and made that issue. cc @mfreed7

[lukewarlow]

Fwiw HTML requires a positive standards position or for chrome LGTMs on an intent to ship to be considered supportive.

Saying that Mozilla have marked their position as positive so that's 1 implementor interested.

I do wonder how this requirement works for a feature such as this which will require multiple PRs to add to the spec?

[domenic]

a feature such as this which will require multiple PRs to add to the spec?

I'm confused why this feature is being done as multiple PRs; it makes review a good deal harder.

[keithamus]

If it makes it easier to review I’m happy to put more into one PR. I figured it would be worthwhile splitting it into the core vs each elements behaviour as I imagine there will be more to discuss with each elements behaviour.

[domenic]

Well, it'd make it easier for me, but I haven't signed up to review yet, so no need to make any changes until we get some more opinions :)

Edited to add: the reason it makes it more difficult is that I don't think we want to accept the feature piecemeal.

[lukewarlow]

As per openui/open-ui#900 (comment) this'll need updating to only fire the event when the action is custom (has a hypen) or is recognised and valid (correct action name on correct element).

TLDR is that this will allow us to add default actions in future without conflicting with user land code.

[lukewarlow]

In openui/open-ui#952 (comment) we resolved that "Invokers v1 will be popover and dialog invoking."

This should help keep this initial PR as small as possible while also avoid the issue of reviewing stuff piecemeal.

So #9875 can be merged into this along with dialog related changes.

[mfreed7]

Fwiw HTML requires a positive standards position or for chrome LGTMs on an intent to ship to be considered supportive.

Saying that Mozilla have marked their position as positive so that's 1 implementor interested.

Chromium is explicitly supportive of this proposal, so I believe it has two implementer support (including Mozilla).

Is this PR in a state that it can get a review? I'm happy to do so, if it'd help.

[keithamus]

I'd be happy to get reviews, I think this is in a good position for that.

[mfreed7]

I'd be happy to get reviews, I think this is in a good position for that.

Done - I added a first set of comments.

[annevk]

I think this now has everything I asked for. Thank you! I think we need at least one more editor review given the many iterations. @zcorpan expressed interest and it seems @foolip is reviewing as well.

[foolip]

I've gone over it all once more and spotted just a few editorial things. Thank you for your patience @keithamus!

[keithamus]

@foolip thanks for the new review! All comments addressed.

[foolip]

Thanks @keithamus, I think we're good to go here. I left two final (really!) suggestions that I hope can be applied without any knock-on effects.

[keithamus]

@foolip thanks! Addressed both of those comments.

[foolip]

Checklist up top looks good, merging this and web-platform-tests/wpt#42664 😄