Function highlightCode

server/utils/code-highlight.ts:266–334

(
  code: string,
  language: string,
  options?: HighlightOptions,
)

 * Each line is wrapped in a span.line for individual line highlighting.
 */
export async function highlightCode(
  code: string,
  language: string,
  options?: HighlightOptions,
): Promise<string> {
  const shiki = await getShikiHighlighter()
  const loadedLangs = shiki.getLoadedLanguages()

  // Use Shiki if language is loaded
  if (loadedLangs.includes(language as never)) {
    try {
      let html = shiki.codeToHtml(code, {
        lang: language,
        themes: { light: 'github-light', dark: 'github-dark' },
        defaultColor: 'dark',
      })

      // Shiki doesn't encode > in text content (e.g., arrow functions)
      html = escapeRawGt(html)

      // Make import statements clickable for JS/TS languages
      if (IMPORT_LANGUAGES.has(language)) {
        html = linkifyModuleSpecifiers(html, {
          dependencies: options?.dependencies,
          resolveRelative: options?.resolveRelative,
        })
      }

      // Check if Shiki already outputs .line spans (newer versions do)
      if (html.includes('<span class="line">')) {
        // Shiki already wraps lines, but they're separated by newlines
        // We need to remove the newlines since display:block handles line breaks
        // Replace newlines between </span> and <span class="line"> with nothing
        return html.replace(/<\/span>\n<span class="line">/g, '</span><span class="line">')
      }

      // Older Shiki without .line spans - wrap manually
      const codeMatch = html.match(/<code[^>]*>([\s\S]*)<\/code>/)
      if (codeMatch?.[1]) {
        const codeContent = codeMatch[1]
        const lines = codeContent.split('\n')
        const wrappedLines = lines
          .map((line: string, i: number) => {
            if (i === lines.length - 1 && line === '') return null
            return `<span class="line">${line}</span>`
          })
          .filter((line: string | null): line is string => line !== null)
          .join('')

        return html.replace(codeMatch[1], wrappedLines)
      }

      return html
    } catch {
      // Fall back to plain
    }
  }