aria-errormessage spec suggests aria-invalid state affects rendering of error element

[AmeliaBR]

During discussion on Twitter, the following passage from the aria-errormessage description caused some confusion:

When an object is in a valid state, it has either aria-invalid set to false or it does not have the aria-invalid attribute. If a valid object has aria-errormessage, the element referenced by aria-errormessage is not rendered because the message it contains is not pertinent.

The phrase "is not rendered" is ambiguous. To an author reading that paragraph, it makes it sound like the rendering change happens automatically.

However, the next paragraph puts the responsibility on the author to manage the rendering of the error message:

When aria-errormessage is pertinent, authors MUST ensure the content is not hidden so users can navigate to and examine the error message. Similarly, when aria-errormessage is not pertinent, authors MUST either ensure the content is not rendered or remove the aria-errormessage attribute or its value.

Suggested text to replace the former paragraph:

When an object is in a valid state, it has either aria-invalid set to false or it does not have the aria-invalid attribute. Authors MAY use an aria-errormessage attribute on an object that is currently valid, but only if the element referenced by aria-errormessage is not rendered, because the message it contains is not pertinent.

In addition, I wonder whether the phrase "is not rendered", in both paragraphs, should be replaced by "hidden", which has an explicit definition in the spec.

[carmacleod]

Or perhaps (slightly shorter):

If a valid object has aria-errormessage, authors MUST NOT render the element referenced by aria-errormessage because the message it contains is not pertinent.

Interesting that "rendered", which is used in a lot of places in the spec, doesn't have an explicit definition. Should it? It is used in the context of AT making strings available as speech/braille, as well as either authors or user agents making something visible or "not hidden". Possibly other contexts, too. Would be a complicated definition. :)