Esm: v3.2.15 regression with babel/register and jest

[dnalborczyk]

the following works with esm v3.14.0 and less, fails with v3.15.0+:

// some.test.js
require = require('esm')(module)
require('@babel/register')
const { someFunc } = require('../')

test('some test', () => {
  expect(true).toBe(true)
})

Test suite failed to run

    /dev/node_modules/@babel/traverse/lib/visitors.js:1
    Error: [BABEL] /dev/packages/component/src/utils/index.js: You gave us a visitor for the node type constructor but it's not a valid type (While processing: "/dev/node_modules/@babel/plugin-proposal-class-properties/lib/index.js")

stack trace

      at verify (../../node_modules/@babel/traverse/lib/visitors.js:130:13)
      at explode (../../node_modules/@babel/traverse/lib/visitors.js:52:3)
      at Object.merge (../../node_modules/@babel/traverse/lib/visitors.js:165:5)
      at Object.<anonymous> (../../node_modules/@babel/helper-replace-supers/lib/index.js:89:46)
      at Object._compile (../../node_modules/pirates/lib/index.js:99:24)
      at Object.newLoader [as .js] (../../node_modules/pirates/lib/index.js:104:7)
      at _helperReplaceSupers (../../node_modules/@babel/helper-create-class-features-plugin/lib/fields.js:22:40)
      at Object.<anonymous> (../../node_modules/@babel/helper-create-class-features-plugin/lib/fields.js:156:4)
      at Object._compile (../../node_modules/pirates/lib/index.js:99:24)
      at Object.newLoader [as .js] (../../node_modules/pirates/lib/index.js:104:7)
      at Object.<anonymous> (../../node_modules/@babel/helper-create-class-features-plugin/lib/index.js:34:15)
      at Object._compile (../../node_modules/pirates/lib/index.js:99:24)
      at Object.newLoader [as .js] (../../node_modules/pirates/lib/index.js:104:7)
      at _helperCreateClassFeaturesPlugin (../../node_modules/@babel/plugin-proposal-class-properties/lib/index.js:19:16)
      at _default (../../node_modules/@babel/plugin-proposal-class-properties/lib/index.js:30:14)
      at ../../node_modules/@babel/helper-plugin-utils/lib/index.js:19:12
      at loadDescriptor (../../node_modules/@babel/core/lib/config/full.js:165:14)
      at cachedFunction (../../node_modules/@babel/core/lib/config/caching.js:33:19)
      at loadPluginDescriptor (../../node_modules/@babel/core/lib/config/full.js:200:28)
      at config.plugins.reduce (../../node_modules/@babel/core/lib/config/full.js:69:20)
          at Array.reduce (<anonymous>)
      at recurseDescriptors (../../node_modules/@babel/core/lib/config/full.js:67:38)
      at loadFullConfig (../../node_modules/@babel/core/lib/config/full.js:108:6)
      at loadOptions (../../node_modules/@babel/core/lib/config/index.js:27:36)
      at OptionManager.init (../../node_modules/@babel/core/lib/index.js:231:36)
      at compile (../../node_modules/@babel/register/lib/node.js:61:42)
      at compileHook (../../node_modules/@babel/register/lib/node.js:102:12)
      at Object._compile (../../node_modules/pirates/lib/index.js:93:29)

@jdalton I can look into creating a test case if you want to keep supporting this scenario.

_(changed versions)_

[jdalton]

Are you sure? There's like 3 commits between the two versions and nothing related to the loader.

[dnalborczyk]

fairly sure, yeah. I swapped between 14 and 15 a couple times.

-> one sec, gonna re-check both caches (babel and esm) just to rule out the cache.

_(updated versions)_

[dnalborczyk]

uuuups, sorry. just noticed you released 16 some minutes ago. the exception started happening with 15.

_(changed title)_

[jdalton]

I'm guessing this change.

Could you create a repro repo?

I can look into creating a test case if you want to keep supporting this scenario.

Yes, please! Thank you!

[dnalborczyk]

@jdalton on second thought, I think I was using jest not the way it was intended.

jest is transforming files implicitly with babel, unless overwritten:
https://jestjs.io/docs/en/configuration.html#transform-object-string-string

it seems bridging with esm somehow invalidates the transform mechanism, hence I explicitly used @babel/register in the test script.

my gut feeling tells me it should be left alone, until esm supports jest officially through transforms. what do you think?

til then I just let jest using babel for es6 module transforms:

// babel.config.js
const {
  env: { NODE_ENV },
} = process

const isTest = NODE_ENV === 'test'
const plugins = ['@babel/plugin-transform-flow-strip-types']

if (isTest) {
  plugins.push('@babel/plugin-transform-modules-commonjs')
}

module.exports = {
  plugins,
}

[jdalton]

If the scenario worked before and now doesn't I'd still like a repro to investigate.

Update:

Related issue https://github.com/nuxt/nuxt.js/pull/5203#issuecomment-472227804

Update:

From https://github.com/standard-things/esm/compare/3.2.14...3.2.15 I think maybe this could be the problem patch https://github.com/standard-things/esm/commit/dd7d96f6a061dfa7f2f138dbc155386ea0345570. It moved setting the prototype after setting properties. I did this because I thought it would allow setting more properties (since if a non-writable property exists on a prototype it will not be written as an own property either). However, it looks like these added properties are causing problems.

Update:

Or more likely this change https://github.com/standard-things/esm/commit/fc232ac087d1d98b5ff40f95bf19281452993015#diff-5708a2c960a8a812847884b65cd4590fR154. As it changes the setting of the constructor as a plain assignment which would preserve non-enumerability to one that forces enumerability.

[dnalborczyk]

hey @jdalton , sorry, been too busy yesterday. looking into repro now ....

_update_:
here you go: https://github.com/dnalborczyk/jest-esm-regression

npm test

I omitted any babel-plugin, babel.config.js etc. as it doesn't seem to be needed to cause the exception.

[ForsakenHarmony]

Also ran into a related issue with webpack validation

configuration.optimization.splitChunks has an unknown property 'constructor'.

[jdalton]

@dnalborczyk Thanks for the repro. Confirmed the patch has fixed it.

Update

esm v3.2.17 is released :tada: