HTML element boolean attribute handling spec conformance

[kellytk]

Description

I'm submitting a ...

• bug report

The handling of the following true condition appears to be out of spec:

let is_disabled = true;

<input disabled=is_disabled,/>

Expected Results

<input disabled>
//or
<input disabled="">
//or
<input disabled=disabled>

Actual Results

<input disabled="true">

Please note the following quotes from the spec:

If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute’s canonical name, with no leading or trailing white space.

A boolean attribute without a value assigned to it (e.g. checked) is implicitly equivalent to one that has the empty string assigned to it (i.e. checked=""). As a consequence, it represents the true value.

The values "true" and "false" are not allowed on boolean attributes. To represent a false value, the attribute has to be omitted altogether.

I expect that the flawed behavior affects all boolean attributes however I've not confirmed that.

For completeness, the following false condition behaves as expected, omitting the disabled attribute entirely:

let is_disabled = false;

<input disabled=is_disabled,/>

<input>

[untitaker]

This is annoying with <textarea> and readonly: Any value of readonly will make the textarea readonly, also this one is permanently readonly:

<textarea readonly=false />

[estk]

Thanks for pointing this out @kellytk . @deniskolodin this is also a problem with elements and the selected attr, the attr's value is always to_string'd, so as you can imagine, the <option> is always selected.