Emphasise that error messages should state each disallowed character

[terrysimpson99]

What

Give a brief description of the style, component or pattern you want to propose.

Why

Explain why you think this should be added to the GOV.UK Design System.

• What evidence do you have that it's needed by multiple services across government?
• What evidence do you have that it meets the needs of the users of those services?
• Have you checked that it doesn't already exist in the GOV.UK Design System?

Anything else

Include links to any examples, research or code to support your proposal, if available.

[terrysimpson99]

Guidance currently refers to two scenarios

1. If the input uses characters that are not allowed and you know what the characters are
2. If the input uses characters that are not allowed and you do not know what the characters are

It doesn't indicate preference for either scenario. I propose guidance is updated to indicate stating each disallowed character in the error message is the default. A recent discussion on slack suggested extra development effort is required to state each disallowed character but it is a legitimate request.

[36degrees]

I've transferred this issue from the backlog repo as it's about making a specific improvement to the guidance for an existing component.