label_for when used with tag_field missing id attribute

[chy-causer]

According to the HTML5 spec, when a label tag contains a for attribute it must accompany a labelable element of matching id. This is to aid usability of forms in browsers as well as to help screen readers.

The following commit adds a failing test that should hopefully explain what I mean:
chy-causer@c4f43e7

I used Mojo::DOM in the test rather than hard-coded the id and for attributes directly because a fully working solution could possibly have to rewrite these attributes. A naive solution of

%= label_for foo => '<Foo>'
%= text_field foo => 'bar'

<label for="foo">&lt;Foo&gt;</label>
<input name="foo" id="foo" type="text" value="bar"> 

may well break HTML validation on existing sites whenever multiple fields for name foo are rendered on a page.

It is possible that this is an intractable problem, and if so, may I please request a short note or example in the docs for label_for and rendering guides indicating that when label_for is used, the input field requires its id attribute to match? I was scratching my head for a bit as to why my label tags were not clickable.

Many thanks.

[kraih]

Thanks, fixed.