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Issues with using a websocket k6 typescript enum type #4540
Description
Brief summary
Using e.g. the EventName.Open type from the k6/experimental/websockets compiles but can't be run
k6 version
k6 v0.56.0 (go1.23.4, darwin/arm64)
OS
MacOS 15.3
Docker version and image (if applicable)
No response
Steps to reproduce the problem
I have some code that can be summarised thus:
import { EventName, Params, WebSocket } from 'k6/experimental/websockets';
...
const ws = new WebSocket(`${websocketHost}/ocpp/1.6/`, null, params);
ws.addEventListener(EventName.Open, () => {
console.log('Connected');
}I can try running it in several ways:
k6 run --compatibility-mode=experimental_enhanced src/idle-station.tsk6pack src/idle-station.ts| k6 run -find ./src -type f -name '*.ts' -exec esbuild '{}' --bundle --outbase=src --outdir=dist --external:k6 --format=esm \;thenk6 run dist/idle-station.js
Expected behaviour
I expect the code to compile and run the test
Actual behaviour
For all of the above methods, I get this runtime error:
ERRO[0000] TypeError: Cannot read property 'Open' of undefined
at idle_station_default (file:///Users/joff/src/chargefox/load-testing/dist/idle-station.js:16:33(19)) executor=shared-iterations scenario=default source=stacktrace
To work around this in the meantime -
I can either use the "open" literal in place of the enum:
ws.addEventListener('open', () => {Although then my IDE complains of TS2345: Argument of type "open" is not assignable to parameter of type EventName
Or I can use a type assertion:
ws.addEventListener(<EventName>'open', () => {Which isn't ideal either
Reacted by Jiayi Hu
Activity
Fernando-hub527 commentedon Feb 21, 2025
Hi, I'm starting to contribute to K6 and would like to help with this issue.
oleiade commentedon Mar 26, 2025
Hey folks 👋🏻
Thanks for taking the time to report this, and cheers @Fernando-hub527 for putting some time into it. Before we start reviewing the PR though, I have a preliminary question: where is this
EventNameconstruct coming from?A quick search didn't show any results in specifications around WebSockets and JS, so I'm a little bit confused. Also, going though the code of the experimental module, it doesn't seem to be a thing. Looking into websockets, it seems the first argument to addEventListener seems to be a static string, on par with the current implementation.
k6 tries to stick as strictly as possible to specifications, especially for protocols/technologies like WebSockets, thus, I'm wondering whether that's an implementation mishap/lack or whether that's a request to add a feature?
I'm definetly not a websockets expert so forgive my potential naivity, but the websockets module doesn't expose an
EventNameeither as far as I can tell, and I genuinely wonder where this expectation came from in the first place; is it something we have documented somewhere? 🙇🏻PS: I will keep the issue in triage while we wait for clarifications
joffotron commentedon Apr 4, 2025
@oleiade Maybe I can help shed some light... the definition appears (already) in
node_modules/@types/k6/experimental/websockets/index.d.ts... which now that I read this more closely makes me think this issue should be filed over on the DefinitelyTyped repo? Unsure about who maintains each type definition over there with respect to each project!?
https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/k6/experimental/websockets/index.d.ts#L210-L240
oleiade commentedon Apr 10, 2025
@joffotron I would suggest indeed to bring it to the DefinitelyTyped repo instead, as I don't think adding this type specifically to the k6 codebase's module adds value 🙇🏻
Also, we maintain it. I believe the way to go would be to open a PR directly on the definitely typed repo, and their bot will ping maintainers automatically.