Yarn 3 does not work with type=module and cypress.config.js

[lmiller1990]

Ref: #22747 -> #22747 (comment)

Repro: yarn3typemodule.zip

Workaround: change cypress.config.js to be named cypress.config.mjs. This should fix the issue. This means anything imported in cypress.config.mjs will need the mjs extension, and you will also need the full extension in the import. Eg:

import { defineConfig } from "cypress";
import { foo } from './foo.mjs' // mjs extension

export default defineConfig({
   e2e: {
      setupNodeEvents(on, config) {
        blah() // can call it here
        return config
      },
   },
})

[JessicaSachs]

+1 but more importantly for pnpm. Should probably prioritize pnpm based on npm trends.

https://npmtrends.com/pnpm-vs-yarn

[MikeMcC399]

This also has implications for documentation.

Currently there is an implicit assumption that either npm or Yarn Classic is being used as package manager. Yarn Modern (version 2 and later) in npmLinker: node-modules mode behaves much like Yarn Classic. Once Yarn Modern Plug'n'Play is used, then the documented instructions get into problems.

pnpm doesn't get much of a mention in the documentation either.

[lmiller1990]

pnpm is basically a drop in replacement, I don't think it has any issues, does it?

Yarn 3 PnP is a huge problem since we are not a standard module, we are entire native electron app, and Yarn tampers with assumptions we really should be able to make about the underlying Node.js engine. I would like to support Yarn 3 better, but we can never really be "zero installs", since our postinstall hook grabs a binary, and I don't think this is something that could be zipped up and stuck inside a git repo like Yarn 3 does with all the modules (this is my understanding of PnP, anyway - no installs since your modules are all committed in a zip file).

[MikeMcC399]

@lmiller1990

pnpm is basically a drop in replacement, I don't think it has any issues, does it?

Since my previous post, pnpm has been added to the Getting Started > Installing Cypress documentation.

It works and it is not specifically relevant to this issue about Yarn 3.

[MikeMcC399]

@lmiller1990

Yarn Modern Plug'n'Play has as an option: zero installs. Don't equate pnp with zero installs though, and I would recommend taking zero installs out of the consideration in the first instance.

In .yarnrc.yml for Yarn Modern, there are three different modes of nodeLinker:

• pnp (default, unless it's a upgrade from Yarn Classic)
• node-modules (default for upgrade from Yarn Classic - compatible with npm and causes no problems for Cypress)
• pnpm (looks like it ought to be identical to the separate pnpm npm module, however it isn't. It doesn't work at all in github-action for instance)

I don't know the solution to this for Cypress!

• I've just been trying to look a bit deeper into it for github-action. I put some of my findings into Implement native Yarn Modern support github-action#969.

[kubijo]

ce we are not a standard module, we are entire native electron app, and Yarn tampers with assumptions we really should be able to make about the underlying Node.js engine. I would like to support Yarn 3 better, but we can never really be "zero installs", since our postinstall hook grabs a binary, and I don't think this is something that could be

Just my two cents to this… I'm using yarn@4 with both PnP & zero-install "enabled" + the enableScripts: false configuration.
The last one helps by preventing unplug on many dependencies… since the existence of post-install script is one thing that triggers the unplug heuristic....

The only thing that I had to do to make cypress work again was to add yarn run cypress install before the startup scripts (since it now doesn't run automatically).

---

All that is just to illustrate a use case and possibly give a hint to others — nothing to do on your side.

[AtofStryker]

This will be fixed with #31520 in Cypress 15

Cypress 12.7.0

Cypress 15 prerelease

[AtofStryker]

I am going to close this issue as it will be resolved with Cypress 15, which is targeted for early July 2025.