claude-code/src/utils/cliHighlight.ts

// highlight.js's type defs carry `/// <reference lib="dom" />`. SSETransport,
// mcp/client, ssh, dumpPrompts use DOM types (TextDecodeOptions, RequestInfo)
// that only typecheck because the hljs import below pulls lib.dom in.
// tsconfig has lib: ["ESNext"] only — this ref preserves the status quo.
/// <reference lib="dom" />

import { extname } from 'path'
// Static import — dynamic import('highlight.js') fails in Bun --compile mode
// because module resolution points to the internal bunfs binary path.
import hljs from 'highlight.js'

export type CliHighlight = {
  highlight: typeof import('cli-highlight').highlight
  supportsLanguage: typeof import('cli-highlight').supportsLanguage
}

// One promise shared by Fallback.tsx, markdown.ts, events.ts, getLanguageName.
let cliHighlightPromise: Promise<CliHighlight | null> | undefined

let loadedGetLanguage: ((name: string) => { name: string } | undefined) | undefined

async function loadCliHighlight(): Promise<CliHighlight | null> {
  try {
    const cliHighlight = await import('cli-highlight')
    // highlight.js CJS interop: `export =` wraps in .default under ESM
    const hljsMod = hljs as { getLanguage?: typeof loadedGetLanguage; default?: typeof hljs }
    loadedGetLanguage = hljsMod.getLanguage ?? hljsMod.default?.getLanguage
    return {
      highlight: cliHighlight.highlight,
      supportsLanguage: cliHighlight.supportsLanguage,
    }
  } catch {
    return null
  }
}

export function getCliHighlightPromise(): Promise<CliHighlight | null> {
  cliHighlightPromise ??= loadCliHighlight()
  return cliHighlightPromise
}

/**
 * eg. "foo/bar.ts" → "TypeScript". Awaits the shared cli-highlight load,
 * then reads highlight.js's language registry. All callers are telemetry
 * (OTel counter attributes, permission-dialog unary events) — none block
 * on this, they fire-and-forget or the consumer already handles Promise<string>.
 */
export async function getLanguageName(file_path: string): Promise<string> {
  await getCliHighlightPromise()
  const ext = extname(file_path).slice(1)
  if (!ext) return 'unknown'
  return loadedGetLanguage?.(ext)?.name ?? 'unknown'
}