CJS plugins file (and ideally also allowing an ESM one)

Especially with Node 10 reaching EOL, and native ESM being used increasingly in Node projects (type: module in package.json), including those which may also house browser code in need of testing, the apparent inability to use at least an index.cjs plugins file with Cypress seems rather problematic. (It complains about the extension; pointing pluginsFile in cypress.json to a .cjs file didn’t work either; only switching to .js works–or removing type: module but that causes problems for Node ESM execution.)

(Please note that I’m not speaking about a @babel/register problem–I mean one simply can’t use a cjs file at all.)

Are there any plans (or workarounds) about this? Thanks!

[giltayar]

A simple workaround, till Cypress enables *.cjs configuration scripts, is to add a package.json in the cypress/plugins and cypress/supportfolders that have the following text in them:

{"type": "commonjs"}

This tells Node.js that all “js” files in this folder are CJS, and Cypress will load them without any problem.

[dbo]

One important detail though is that since the plugins file is commonJS, the only way to use your esm modules is via dynamic import, e.g.

const webpackPreprocessor = require("@cypress/webpack-preprocessor");

module.exports = async (on, config) => {
    const {default: webpackOptions} = await import("../../webpack.config.mjs");

    on("file:preprocessor", webpackPreprocessor({
        webpackOptions,
    }));
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