Function transformMiddleware

packages/vite/src/node/server/middlewares/transform.ts:112–384

(
  server: ViteDevServer,
)

}

export function transformMiddleware(
  server: ViteDevServer,
): Connect.NextHandleFunction {
  // Keep the named function. The name is visible in debug logs via `DEBUG=connect:dispatcher ...`

  // check if public dir is inside root dir
  const { root, publicDir } = server.config
  const publicDirInRoot = publicDir.startsWith(withTrailingSlash(root))
  const publicPath = `${publicDir.slice(root.length)}/`

  return async function viteTransformMiddleware(req, res, next) {
    const environment = server.environments.client

    if (
      (req.method !== 'GET' && req.method !== 'HEAD') ||
      knownIgnoreList.has(req.url!) ||
      isDocumentFetchDest(req)
    ) {
      return next()
    }

    let url: string
    try {
      url = decodeURI(removeTimestampQuery(req.url!)).replace(
        NULL_BYTE_PLACEHOLDER,
        '\0',
      )
    } catch (e) {
      if (e instanceof URIError) {
        server.config.logger.warn(
          colors.yellow(
            `Malformed URI sequence in request URL: ${removeTimestampQuery(req.url!)}`,
          ),
        )
        return next()
      }
      return next(e)
    }

    const withoutQuery = cleanUrl(url)

    try {
      const isSourceMap = withoutQuery.endsWith('.map')
      // since we generate source map references, handle those requests here
      if (isSourceMap) {
        const depsOptimizer = environment.depsOptimizer
        if (depsOptimizer?.isOptimizedDepUrl(url)) {
          // If the browser is requesting a source map for an optimized dep, it
          // means that the dependency has already been pre-bundled and loaded
          const sourcemapPath = url.startsWith(FS_PREFIX)
            ? fsPathFromId(url)
            : normalizePath(path.resolve(server.config.root, url.slice(1)))
          // url may contain relative path that may resolve outside of the optimized deps directory
          if (!depsOptimizer.isOptimizedDepFile(sourcemapPath)) {
            return next()
          }
          try {
            const map = JSON.parse(