Refactor createShikiHighlighter

[bluwy]

Changes

(Disable whitespace diff recommended)

• Refactors the createShikiHighlighter API to:
  • return codeToHast and codeToHtml. The hast version allows the rehype plugin to syntax highlight more efficiently. Before it's hast -> text -> (highlight) hast -> html -> hast , now it's hast -> text -> (highlight) hast.
  • reduce initial options surface as they aren't needed for the creation of the shiki highlighter. This allows the <Code/> component to key by lesser values and improve sharing the cached highlighter.

Testing

Existing tests should pass. Also edited stuff due to new API names.

Docs

There's a few changesets, but .changeset/large-zebras-sniff.md is the main one for the astro major, which will go in the migration guide.

[changeset-bot]

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Latest commit: 65bb472

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[github-actions]

This PR is blocked because it contains a major changeset. A reviewer will merge this at the next release if approved.

base branch is next (still awaiting docs review before merging)

[matthewp]

is this cast safe? we know there's at least 1 child and its an Element?

[bluwy]

Yeah it should be. We currently control this function (it's mostly internal details for Shiki only), so if it changes we can also tweak this here.

[matthewp]

just the one thing to confirm, otherwise lgtm

[github-actions]

This PR is blocked because it contains a major changeset. A reviewer will merge this at the next release if approved.

[sarah11918]

Thanks @bluwy ! Just made some suggestions for your consideration that try to highlight more when someone might encounter the problem, because Shiki is pretty commonly used, but maybe transformers not quite as much! So something like this makes it maybe more obvious when someone needs to care and pay attention.