Apologies if this is a common question -- I searched the FAQ but I don't think I saw anything https://github.com/whatwg/html/blob/main/FAQ.md

Is there a canonical representation of the HTML spec in a machine readable-format like XML or JSON as opposed to the IDL?

For example, the spec would specify that the type on a button is an "enumerated attribute" that can take "button" "submit", etc. as opposed to the IDL, which specifies a DOM String

if you want to parse source, you'd be best off using or extending wattsi https://github.com/whatwg/wattsi

That makes sense. I had a look at I am impressed it is maintained and in Pascal. I agree that parsing wattsi sources (and potentially using wattsi itself) makes sense due to the useful dfntag especially. For example in the case of button, it is helpful that dfn holds context for attributes:

  <table>
   <thead>
    <tr>
     <th> Keyword
     <th> State
     <th> Brief description
   <tbody>
    <tr>
     <td><dfn attr-value for="button/type"><code
     data-x="attr-button-type-submit">submit</code></dfn>
     <td><span data-x="attr-button-type-submit-state">Submit Button</span>
     <td>Submits the form.
    <tr>
     <td><dfn attr-value for="button/type"><code data-x="attr-button-type-reset">reset</code></dfn>
     <td><span data-x="attr-button-type-reset-state">Reset Button</span>
     <td>Resets the form.
    <tr>
     <td><dfn attr-value for="button/type"><code
     data-x="attr-button-type-button">button</code></dfn>
     <td><span data-x="attr-button-type-button-state">Button</span>
     <td>Does nothing.
  </table>
  <table>
   <thead>
    <tr>
     <th> Keyword
     <th> State
     <th> Brief description
   <tbody>
    <tr>
     <td><dfn attr-value for="button/type"><code
     data-x="attr-button-type-submit">submit</code></dfn>
     <td><span data-x="attr-button-type-submit-state">Submit Button</span>
     <td>Submits the form.
    <tr>
     <td><dfn attr-value for="button/type"><code data-x="attr-button-type-reset">reset</code></dfn>
     <td><span data-x="attr-button-type-reset-state">Reset Button</span>
     <td>Resets the form.
    <tr>
     <td><dfn attr-value for="button/type"><code
     data-x="attr-button-type-button">button</code></dfn>
     <td><span data-x="attr-button-type-button-state">Button</span>
     <td>Does nothing.
  </table>

Here is a very rough example:

<h4 split-filename="form-elements">The <dfn element><code>button</code></dfn> element</h4>

<element name="button">
  <categories>
    Flow content, Phrasing content, Interactive content, Palpable content
    Listed, Labelable, Submittable, Autocapitalize-and-autocorrect inheriting
  </categories>

  <contexts>
    Where phrasing content is expected
  </contexts>

  <content-model>
    Phrasing content, no interactive content descendant, no tabindex attribute descendant
  </content-model>

  <attributes>
    Global attributes
    disabled, form, formaction, formenctype, formmethod, formnovalidate, formtarget
    name, popovertarget, popovertargetaction, type, value
  </attributes>

  <accessibility>
    <link href="https://w3c.github.io/html-aria/#el-button">For authors</link>
    <link href="https://w3c.github.io/html-aam/#el-button">For implementers</link>
  </accessibility>
...

~Aside: is there interest in moving wattsi in over to Rust? Matching the existing spec~

Edit: re-read, looks like yes

I'd be ideal if eventually we moved everything from Wattsi to Rust.

How do we want to handle https://github.com/whatwg/html/pull/10557 ? It looks like the boxes in OP are ticked, but it's not clear if it's web compatible yet, and there was at least one crbug filed about <select><input> (https://issues.chromium.org/issues/379612186) cc annevk

(For https://issues.chromium.org/issues/379034733#comment6 , that should be fixed in the spec PR, but maybe not yet in chromium)

Maybe jarhar can give us an update on the shipping plans? Is Chromium still proceeding to ship exactly what's in the PR?

I think it might be reasonable to delay landing until it's baked in stable for a while, but we could also land and revert if it's not able to make it.