ESM Support

[rostislav-simonik]

Short intro

When I took over the maintenance of nexus-prisma, some work was already done to support esm build. I assumed it works, and when I cut a new release the esm build was exposed to esm projects. What introduced a few issues

• ES imports doesn't work? #141
• Cannot Import ES Module #641

Some discussion before

• ESM not compatible? #200

Status

esm support was started merely finished. It requires much more work to do. It's not hard to do. Over the weekend I almost converted the whole package to support esm, but it end up creating a polymorphic project supporting both commonjs and esm.

Changes required to do

1. Fixing directory and relative imports

ESM modules don't support folder imports and relative imports without specifying file extensions.

from

import { DMMF } from '@prisma/client/runtime'

import { d } from '../helpers/debugNexusPrisma'
import { Module } from './helpers/types'
import { ModuleGenerators } from './ModuleGenerators'
import { Settings } from './Settings'

to

import { DMMF } from '@prisma/client/runtime/index.js'

import { d } from '../helpers/debugNexusPrisma.js'
import { Module } from './helpers/types.js'
import { ModuleGenerators } from './ModuleGenerators/index.js'
import { Settings } from './Settings/index.js'

2. Supporting __dirname

__dirname __filename are not supported by esm modules. There is an alternative using import.meta.url.

So we would need to have something like this in each file that requires __dirname:

import { fileURLToPath } from 'url';
import { dirname } from 'path';

let __filename: string, __dirname: string;

if (typeof process !== 'undefined' && process.versions.node) {
    // Node.js environment, could be either CommonJS or ESM
    if (typeof __filename !== 'undefined') {
        // We are in CommonJS
        __dirname = dirname(__filename);
    } else {
        // We are in ESM
        // @ts-ignore
        __filename = fileURLToPath(import.meta.url);
        __dirname = dirname(__filename);
    }
} else {
    // Not a Node.js environment, won't handle this case
    throw new Error('Cannot determine runtime environment');
}

console.log('Current file:', __filename);
console.log('Current directory:', __dirname);

3. Imports of commonjs packages with default export

If we are importing commonjs default export, then it needs to be treated differently in commonjs and esm,

in commonjs

import dedent from 'dindist';

in esm

import dindist from 'dindist';
const dedent = dindist.default

we could end up with the following snippet

import dindist from 'dindist';
const dedent = dindist.default || dindist

4. Some more

I haven't finished but could be more challenges to overcome

Do we need esm build at this moment?

I think It's not needed, commonjs version can still be used in esm project. And I think it would be good if nexus, prisma will support first, and then we can add support for nexus-prisma

What's next

I will release a patch to remove esm build #696, so it's not present in the published version. I'll also include e2e test to test commonjs version of nexus-prisma in esm projects.

Feel free to write your thoughts about this.