Transition package from CJS to ESM

[christian-bromann]

As part of the v8 effort we are currently migrating over to ESM as many packages will stop support CJS in the future. This means we have to transition all plugins to ESM as well, ideally with continuous support for CJS.

[chmanie]

Nice! Do you have any form of general migration guide that also touches on the topic of keeping support for CJS?

[christian-bromann]

Not really but I would refer to this document: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c#how-can-i-move-my-commonjs-project-to-esm. In regards of supporting both: I don't have a clear solution to this but I plan to have a compiler (e.g. rollup, maybe another TS config) that bundles the files as CJS modules. The package.json then needs to look like this:

  "main": "./build/index.cjs.js",
  "type": "module",
  "module": "./build/index.js",
  "exports": {
    ".": [
      {
        "import": "./build/index.js",
        "require": "./build/index.cjs.js"
      },
      "./build/index.cjs.js"
    ]
  },
  "types": "./build/index.d.ts",
  "typeScriptVersion": "3.8.3",

[christian-bromann]

Update: my initial assumption that CJS services/reporters would stop working when running WebdriverIO within ESM context is wrong. They continue to work as is without any changes required. However I still suggest to do this ESM transition eventually as dependencies might migrate to ESM and stop working. Given WebdriverIO dynamically imports services and plugins there is no need to build a hybrid package for CJS and ESM. Plugins can just export ESM code and it will work fine for users running CJS and ESM.