k6-es6 example not working

[joostmeijles]

The JS compatibility mode documentation (https://docs.k6.io/docs/javascript-compatibility-mode), points to an example that does not work: https://github.com/MStoykov/k6-es6

Running the k6-es6 example results in:

ERRO[0001] TypeError: util.promisify requires a true ES5 environment at file:///C:/Repos/k6-es6/build/app.bundle.js:8:273234(42)

[mstoykov]

@joostmeijles can you provide the script that doesn't work?
Also this is probably better for the k6-es6 repo as it is the one that is trying to do the job of translating ES6+ to ES5.1 that k6 can then run. But lets continue here for now :)

[joostmeijles]

@mstoykov I cloned Github repo and the followed the steps from the README:

npm install
npm run-script webpack
k6 run build/app.bundle.js

Using Node v10.16.2 and K6 v0.26.0 (dev build, go1.13, windows/amd64) on Windows 10.

[mstoykov]

I was mostly asking for the script that didn't work (or better smaller example that showcases it).
But looking at this again util.promisify is about promises and async stuff and k6 currently doesn't have an event loop, so it's totally normal that running through k6-es6 won't help at all.

Does the script work before you run it through k6-es6, because that will be an interesting problem as well? But in general, if it doesn't work without running it through k6-es6 it is very doubtful it will after.

Also as it is mentioned k6-es6 is a proof-of-concept. I would really prefer it if we can extend it and make it work for everything, but it won't work for anything that k6 conceptually doesn't support

[joostmeijles]

The problem is that the example uses xml2js.

Simple fix would be to remove that and update the docs with the event loop limitations.

[simskij]

Thank you for your report! I will have a look at this as soon as I get some time on my hands. 🙏🏼

[mstoykov]

I did try to make it work, as supposedly it should be able to,but all my tries were in vain.

Fortunately @simskij who has some knowledge about how webpack works will have more success.

[simskij]

Hey,

I've been looking at this for the last couple of days and, unfortunately, it seems like we currently are unable to run xml2js, and cheerio for that matter, in --compatibility-mode=base with only @babel/preset-env due to limits in how webpack polyfills dependencies.

The most memory efficient solution for now seems to be to run it without --compatibility-mode=base, rather than trying to polyfill with for instance @babel/polyfill, which while it works - produces roughly the same result with more effort.

Simme

[simskij]

For future reference:

All of these tests have been run with --vus 100 --paused.

Base	Config	Memory Consumption	Comment
✅	@babel/preset-env and useBuiltIns: 'usage'	N/A	Errors out
✅	@babel/preset-env, @babel-polyfill and useBuiltIns: 'entry'	6.3GB	Requires import in test script
❌	@babel/preset-env and useBuiltIns: 'usage'	6.3GB
❌	@babel/preset-env, @babel-polyfill and useBuiltIns: 'entry'	6.5GB	Requires import in test script
✅	@babel/preset-env and useBuiltIns: 'usage'	234mb	without cheerio and xml2js

[simskij]

I've updated the docs as suggested. Closing this issue for now.

Thank you for bringing this to our attention!