Open
Description
The Input Fields article lacks documentation for error messages. We should instruct when those are needed (always when a field can become invalid), that there are default error messages, and how to customize them. It would be nice to also briefly explain how to write good error messages.
Note, Checkbox and RadioButton don't provide error messages. We need to add a caveat that explicitly calls this out.
Besides, this part seems to be no longer relevant as the required indicator is displayed permanently nowadays:
The required indicator is displayed only when the field is empty.