Comment by tannhaeuser | Hacker News Reader

Comment by tannhaeuser | Hacker News Reader

How is this checking the content type of HTML elements? The content type of eg. the table element in HTML 5.1 is given by the following production (from [1]):

    <!-- The table element
     Content: In this order:
     optionally a caption
     element, followed by zero
     or more colgroup
     elements, followed
     optionally by a thead
     element, followed by
     either zero or more tbody
     elements or one or more
     tr elements, followed
     optionally by a tfoot
     element, optionally
     intermixed with one or
     more script-supporting
     elements. -->
    <!ELEMENT table - - 
     (caption?,colgroup*,
      thead,
      (tbody*|tr+),tfoot?)
     +(%scripting;)>

Regular content types are pretty fundamental to markup languages.

[1] http://sgmljs.net/docs/w3c-html51-dtd.html

I think this is mostly answered in the README. This is probably the most relevant section:

> The structure validation is simplistic by necessity, as it defers to the type system: a few elements will have one or more required children, and any element which accepts children will have a restriction on the type of the children, usually a broad group as defined by the HTML spec. Many elements have restrictions on children of children, or require a particular ordering of optional elements, which isn't currently validated.

It's not complete or thorough at present.

Regarding your link: I'm impressed someone took the time to write a DTD for HTML5!

Thanks! The DTD is described in the talk/paper I gave at XML Prague 2017 linked from [1]. Meanwhile, I've got a revised version for HTML 5.2 with basic coverage of the validator.nu test suite, though not published on the site yet.

[1]: http://sgmljs.net/blog/blog1701.html

Since the macro is procedural, I suppose it's feasible to pass a DTD, XML Schema or Relax NG to typed-html so it would work with any XML. Ideally with checking of ID and IDREF or key/keyref.

The question is then can Rust's macros (or what typed-html's technique is called) encode static/compile-time type checking for regular content models, with SGML-like content exceptions and, to top it, with SGML/HTMLish omitted tag inference?

Reply on news.ycombinator.com