direct deep imports prefers .js over .mjs files

[sventschui]

Describe the bug

serverPluginModuleResolve currently prefers .js files over .mjs files when using direct deep imports.

A quick&dirty fix would be to replace the .js with an .mjs extension and serve that file if it exists. Not sure what a proper solution would be.

Reproduction

Add the following import to a basic vite setup:

import { Kinds } from 'graphql/language/kinds';

(See https://github.com/sventschui/vite-mjs-repro)

System Info

• required vite version: `=> 0.14.2
• required Operating System: OS X
• required Node version: 13.12.0

Logs (Optional if provided reproduction)

Browser console:

Uncaught SyntaxError: The requested module '/@modules/graphql/language/kinds' does not provide an export named 'Kinds'

[marvinhagemeister]

Dug a bit into this and the origin is in resolve-from. Internally it calls a private node resolution method:

Module._resolveFilename(moduleId, {
  id: fromFile,
  filename: fromFile,
  paths: Module._nodeModulePaths(fromDirectory)
});

Trouble is that node has no knowledge of the module field in package.json. It's something exclusively used by bundlers.