[whatwg] Form element invalid message

Jukka K. Korpela jkorpela at cs.tut.fi
Wed Jul 27 20:37:09 PDT 2011

28.07.2011 03:21, Ian Hickson wrote:

> A text input field could have a number of error conditions:

Indeed. Therefore it would be essential to be able to set the error 
message for _each_ check that a browser is supposed to do on the basis 
of HTML markup alone. If this is not possible, it is easier to authors 
to code all data checking in JavaScript. Setting the error messages is 
important both for context dependency and for localization (using the 
language of the browser's UI would be odd when it differs from the 
language of the page - if the page is in Greek and the instructions 
there are in Greek, I would expect the messages of the data error to be 
Greek, even when my browser speaks Hebrew).

> I guess we can have a dedicated attribute that user agents can use
> to provide a message, rather than the current solution of just using the
> title="" attribute for pattern=""'s error message.

The title="" attribute is generally supposed to contain an advisory 
title for an element, and deviating from this that way is very odd and 
confusing - especially since user agents may show its value in a tooltip 
or speak it out when entering the field.

A dedicated attribute is much better. In particular, it does not 
interfere with the existing use of existing attributes.

> If it's present, user
> agents could use it to replace or augment their message, and authors could
> make the message more specific by dynamically changing the attribute when
> during the 'invalid' event handler.
>     <label>  Offer code:
>      <input type=text maxlength=8 pattern="[a-z1-9]+" required
>             oninput="setCustomValidity(input.match(/0/) ?
>                      'Codes contain no zeroes, only Os.' : '')"
>             validitymessage="Enter the code without spaces.">
>     </label>

It would be more logical and descriptive to call it errormessage rather 
than validitymessage.

But the main problem is that attributes like maxlength, pattern, and 
required are supposed to provide some data validation in a simple manner 
that does not need to involve JavaScript and works even when it is 
disabled. To make them useful, it should be possible to set the error 
message for each of them separately in HTML.

I have no better solution than to use separate attributes, like 
maxlengtherror, patternerror, requirederror. This doesn't sound cool, 
but it would work and would be useful.

Yucca, http://www.cs.tut.fi/~jkorpela/

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