Correction: conditionally revise allowed attributes and roles on summary element

[scottaohara]

Normative follow-on from #434

The spec was updated to note that the summary element doesnt' always map to the button element. The allowed attributes indicated that all attributes that were applicable to the button role were allowed. However, in practice this doesn't make sense and could break or be in contradiction to the implicit semantics.

The allowed aria-* attributes for the button role include

• aria-disabled
• aria-haspopup
• aria-expanded
• aria-pressed

Edit: after testing, aria-expanded and aria-pressed provide zero value on a summary element, as they are presently ignored by user agents (browsers/AT). https://codepen.io/scottohara/pen/ZEjZPoR

markup and results of linked codepen

<details open>
	<summary aria-pressed=false>test 1</summary>
	aria-pressed on summary element
</details>
<details open>

<summary aria-expanded=false>test 2</summary>

aria-expanded=false on summary element

</details>
<details open>

<summary aria-haspopup=dialog>test 3</summary>

aria-haspopup=dialog on summary element

</details>
<details open>

<summary aria-disabled=true>test 4</summary>

aria-disabled=true on summary element

</details>

test 1
JAWS/NVDA+Chromium/Gecko - attribute ignored
Narrator+Edge - attribute ignored / UIA ignores attr
iOS/macos safari/firefox+VO - ignored

test 2
JAWS/NVDA+Chromium/Gecko - attribute ignored
Narrator+Edge - attribute ignored / UIA ignores attr
iOS/macos safari/firefox+VO - ignored

test 3
JAWS/NVDA+Chromium/Gecko - announces as a button menu
Narrator+Edge - has popup
macOS VO + Safari - has popup
iOS VO + safari, macOS VO firefox - ignored

test 4
JAWS/NVDA+Chromium/Gecko - disabled state conveyed
Narrator+Edge - disabled
iOS/macOS Safari/firefox+VO - disabled

Concerning the allowed roles for a summary element. A summary element can be one of two things, the 'summary for its parent details' - where it acts as the triggering element for the disclosure widget. Or, if it doesn't meet the conditions to be that (e.g., it is not a child of a details element, or it is not the first instance of a summary element - e.g., it's the 2+ summary element within a details), then it is treated as a generic element, so any role/attribute should be allowed.

test cases - https://w3c.github.io/html-aria/tests/summary-allowances.html

• HTML Validator
• IBM equal access accessibility checker
• axe-core
• ARC toolkit

(linked issues to each checker referenced in the following thread)

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