Bundling SSR Modules using CommonJS exports alias results in ReferenceError: exports is not defined

Problem

Describe the bug When importing an SSR module, if - it uses the `exports` alias instead of `module.exports`, - `ssr.noExternal` is declared with the module Vite is unable to evaluate it. This can also happen with the more common `module.exports`, but seems to not be guaranteed. While this behavior may seem esoteric due to modern proliferation of `module.exports`, this is a feature of Node since v0.1.16 and has not been deprecated. In addition, there are instances of various npm modules in the wild which use this method of exporting fields, including, but not limited to: - chokidar - cookie - consolidate - d3 (node) - @material-ui/core - mysql2 - topcoat-preact ...and much, much, more searchable on GitHub. I believe this is also an output of some bundlers. Reproduction https://github.com/GrygrFlzr/vite-cjs-ssr [code block] Visit http://localhost:3000 to trigger SSR, which consists of a very simple script that uses the `cookie` npm module. The page will render `exports is not defined` and errors will show up in the server console: [code block] System Info - `vite` version: 2.1.2 - Operating System: Windows 10 10.0.19042 - Node version: 14.16.0 - Package manager and version: npm 6.14.11