Add ability to output as .mjs file

[dennisameling]

I have "type": "module" set in my package.json, and I'd like to output my app as an .mjs file. However, when I set outputFormat: 'esm' in this app, it builds with the regular .js extension. This means that when I'm packaging my app as ZIP for AWS Lambda, I have to copy the package.json file into it (using the vite-plugin-static-copy plugin), so that Node understands that it should handle the dist/main.js file as an ESM file instead of CommonJS.

It'd be great if the generated file could use the .mjs file extension, so that I don't have to add the package.json file into my ZIP.

Here's my current vite.config.ts:

import { defineConfig } from 'vitest/config'
import tsconfigPaths from 'vite-tsconfig-paths'
import { VitePluginNode } from "vite-plugin-node";
import { viteStaticCopy } from "vite-plugin-static-copy";

export default defineConfig({
    plugins: [
        tsconfigPaths(),
        ...VitePluginNode({
            adapter: 'express',
            appPath: './src/main.ts',
            exportName: 'myApp',
            outputFormat: 'esm'
        }),
        viteStaticCopy({
            targets: [
                {
                    src: 'package.json',
                    dest: '.'
                }
            ]
        })
    ],
})

[withxat]

I’ve never used Amazon Lambda, but the output is managed by Vite, which is powered under the hood by Rollup. You can achieve this by using the following configuration:

import { defineConfig } from 'vite';

export default defineConfig({
  build: {
    rollupOptions: {
      output: {
        entryFileNames: `[name].[hash].mjs`, // or just [name].mjs
        chunkFileNames: `[name].[hash].mjs`,
      },
    },
  },
});

Hope this helps! :)