Adding language ID to the class attribute

[hasparus]

👋 Hello. Firstly, thank you for shiki-twoslash. It's amazing.

I'd like to post this as a humble feature request.

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Problem

Knowing the language of the code snippet in CSS may be quite useful in a few cases.

AFAIK it's not possible right now with remark-shiki-twoslash without a second pass with a rehype plugin?

Possible Solution

The remark plugin could accept a configuration option to set attributes of the pre element at the root of the code block.
This would later be used in preOpenerFromRenderingOptsWithExtras in shiki-twoslash.

Workaround

I used pnpm patch to quickly add opts.langId to the classList in preOpenerFromRenderingOptsWithExtras.

twoslash/packages/shiki-twoslash/src/renderers/plain.ts

Lines 12 to 18 in eb286da

	export const preOpenerFromRenderingOptsWithExtras = (opts: HtmlRendererOptions, meta: Meta, classes?: string[]) => {
	const bg = opts.bg || "#fff"
	const fg = opts.fg || "black"
	const theme = opts.themeName || ""
	// shiki + `class` from fence + with-title if title exists + classes
	const classList = ["shiki", theme, meta.class, meta.title ? "with-title" : "", ...(classes || [])]

[orta]

Yep, I think this is totally reasonable 👍🏻