Declarative Section Type Matching with helix-markup.yaml

[trieloff]

This is an extension of #516 and depends on #533

So far, helix-markup.yaml is capable of matching DOM elements and lower-level MDAST structures, but when it comes to sections, the features provided by #533 include only the ability to:

• control which of the inferred types from content.section[].types should show up in the section tag's class attribute
• control if a section should be rendered as a div (default), section, nav, main, header, footer, or any other HTML element

With this extension, developers will furthermore be able to:

• control which types are inferred without using utils.types imperatively
• infer section types based on URL patterns

For this, helix-markup.yaml will get a new optional key, sections:

sections:
  navigation:
    content: ^heading? list+$
    uri: /nav.html

markup:
  navigation:
    match: section[@type=navigation]
    type: markdown
    wrap: nav

In the example above, if a URL matching /nav.html (we support URI Template expressions) is requested, and there is a section containing one optional heading at the beginning and a series of lists, then that section should get a type with the value navigation (in addition to the automatically inferred types).

In the second part of the example, sections in MDAST with a type that contains navigation are getting wrapped in nav elements.

/cc @davidnuescheler