indexHtmlMiddleware() — vite Function Reference

Source Code

packages/vite/src/node/server/middlewares/indexHtml.ts lines 442–542

export function indexHtmlMiddleware(
  root: string,
  server: ViteDevServer | PreviewServer,
): Connect.NextHandleFunction {
  const isDev = isDevServer(server)
  const fullBundleEnv =
    isDev && server.environments.client instanceof FullBundleDevEnvironment
      ? server.environments.client
      : undefined

  // Keep the named function. The name is visible in debug logs via `DEBUG=connect:dispatcher ...`
  return async function viteIndexHtmlMiddleware(req, res, next) {
    if (res.writableEnded) {
      return next()
    }

    const url = req.url && cleanUrl(req.url)
    // htmlFallbackMiddleware appends '.html' to URLs
    if (url?.endsWith('.html') && req.headers['sec-fetch-dest'] !== 'script') {
      if (fullBundleEnv) {
        const pathname = decodeURIComponent(url)
        const filePath = pathname.slice(1) // remove first /

        let file = fullBundleEnv.memoryFiles.get(filePath)
        if (!file && fullBundleEnv.memoryFiles.size !== 0) {
          return next()
        }
        const secFetchDest = req.headers['sec-fetch-dest']
        if (
          [
            'document',
            'iframe',
            'frame',
            'fencedframe',
            '',
            undefined,
          ].includes(secFetchDest) &&
          ((await fullBundleEnv.triggerBundleRegenerationIfStale()) ||
            file === undefined)
        ) {
          file = { source: await generateFallbackHtml(server as ViteDevServer) }
        }
        if (!file) {
          return next()
        }

        const html =
          typeof file.source === 'string'
            ? file.source
            : Buffer.from(file.source)
        const headers = isDev
          ? server.config.server.headers
          : server.config.preview.headers
        return send(req, res, html, 'html', { headers, etag: file.etag })
      }

      let filePath: string
      if (isDev && url.startsWith(FS_PREFIX)) {
        filePath = decodeURIComponent(fsPathFromId(url))
      } else {
        filePath = normalizePath(
          path.resolve(path.join(root, decodeURIComponent(url))),
        )
      }

      if (isDev) {
        const servingAccessResult = checkLoadingAccess(server.config, filePath)
        if (servingAccessResult === 'denied') {
          return respondWithAccessDenied(filePath, server, res)
        }
        if (servingAccessResult === 'fallback') {
          return next()
        }
        servingAccessResult satisfies 'allowed'
      } else {
        // `server.fs` options does not apply to the preview server.
        // But we should disallow serving files outside the output directory.
        if (!isParentDirectory(root, filePath)) {
          return next()
        }
      }