msw 2.13+ fails to start up on Jest

[GarrisonD]

It's a follow-up for #2698

Unfortunately this didn't help me:

  "transform": {
    "^.+\\.(js|mjs|ts|tsx)$": "babel-jest"
  },

I had to add @babel/plugin-transform-modules-commonjs to the dev dependencies and specify it in the config. So the changes to my Jest config looks like this:

  "transform": {
-    "^.+\\.(t|j)s$": "ts-jest"
+    "^.+\\.(t|j)s$": "ts-jest",
+    "^.+\\.mjs$": [
+      "babel-jest",
+      { "plugins": ["@babel/plugin-transform-modules-commonjs"] }
    ]
  },

[GarrisonD]

Just wondering: does it still make sense to produce a CJS build for msw if it can't be just used in Node.js? @kettanaito

[kettanaito]

The issue likely occurs because tsup doesn't translate ESM-only dependencies to be importable from within the CJS bundle. That'd be my guess. I have no idea why that happens. But you are right, we are going to drop the CJS build altogether later this year as a part of 3.0.

Do you experience the same issues on Vitest+CJS? Jest is historically bad with ESM, I would not seriously treat it as the expected behavior here.