Add 'aria-errormessage' to definitions list

[AutoSponge]

context:

axe-core/lib/commons/aria/index.js

Line 51 in 645d1fa

'aria-expanded': {

spec: https://www.w3.org/TR/wai-aria-1.1/#aria-errormessage

Suggested fix: insert

	'aria-errormessage': {
		type: 'idref'
	},

[WilcoFiers]

I have some reservations about allowing this into axe-core just yet. Do you know if there are any assistive technologies that support this yet? We have a policy of only taking in accessibility feature that have sufficient support. The only exception to that being, those features that wouldn't get in the way if they weren't support. I don't think that's the case here, but certainly open to some counter-arguments.

[AutoSponge]

@WilcoFiers, as far as I know, aria-errormessage is not supported by browser/AT yet. Currently, techniques that use aria-describedby to link the error message read out when the linked element is focused. The error message is also read out when using role=alert or aria-live=assertive.

I see three options here:

Option 1

Replacing aria-describedby with aria-errormessage and continued use of aria-live (adoption now)

PRO:

• the error message will read out when the error is added
• the code will be spec compliant
• will have future functionality when aria-errormessage is widely supported
• sends message to AT community is ready to support the feature

CON:

• focus element with current error state will not read out

Option 2

Use both aria-describedby and aria-errormessage and continued use of aria-live (adoption now)

PRO:

• the error message will read out when the error is added
• will have future functionality when aria-errormessage is widely supported.
• focus element with current error state will read out
• sends message to AT community is ready to support the feature BUT requires AT to plan for conflict (see below)

CON:

• when aria-errormessage becomes widely available, IF AT chooses to read both aria-describedby and aria-errormessage, the error message will be read twice on focus. Otherwise, aria-errormessage must proceed aria-describedby when both exist.

Option 3

No changes to current pattern (opposes adoption now)

PRO:

• No need to change code/patterns

CON:

• AT may never implement since no one codes for it or is ready to support it

[WilcoFiers]

@AutoSponge Sounds good. I agree, if aria-errormessage was to point to a live region, or if it pointed to the same element as aria-describedby, I think it should pass axe-core. Are you interested on working on a PR for this? If not I think we can leave it on the issue board and we'll get to it when we can.

[AutoSponge]

Great! I will start work on a PR.

[DavidMacDonald]

JAWS appears to support it in browsers.