Allow policies to be written using JavaScript

[flavio]

Kubewarden does not have a JavaScript SDK yet. Recent work done inside of the Bytecode Alliance made possible to compile JavaScript code into WebAssembly. This means it's now possible to create such a Kubewarden SDK.

I've made a small prototype, I think we can pull this off by using the following components:

• Javy: this is the JavaScript -> WebAssembly compiler created by the Bytecode alliance
• Our own Javy plugin to expose custom functions to the Wasm guest
• A JS native library that wraps up the communication between the host and the guest.

The JS policies are going to be compiled as WASI policies and will implement our WASI SDK pattern.

[esosaoh]

Hi @flavio, I'm interested in contributing to this project for Google Summer of Code 2025. I have experience with JavaScript/ TypeScript and am currently learning Kubernetes.

I've been exploring the codebase and I have a couple of questions:

1. For the "JS native library," am I correct in assuming that this would mean developing an API for defining policies in JavaScript? If so, would this API be similar to existing Kubewarden SDKs (go, rust)?

2. How can we verify that our compiled JavaScript WebAssembly module adheres to the Kubewarden WASI pattern?

3. What’s the general process for getting mentorship for GSoC? I'd appreciate any guidance on how to get started.

Looking forward to learning more and contributing!

[flavio]

1. For the "JS native library," am I correct in assuming that this would mean developing an API for defining policies in JavaScript? If so, would this API be similar to existing Kubewarden SDKs (go, rust)?

I've updated the issue description to include a link to the prototype.

We need to write code similar to this. The linked code implements the network capabilities of Kubewarden.

2. How can we verify that our compiled JavaScript WebAssembly module adheres to the Kubewarden WASI pattern?

We could use kwctl to run test policies that use host capabilities to make sure they work as expected.
To be honest, we are lacking a formal e2e test suite (with e2e I mean: build to wasm, run the wasm module with kwctl) that does that for the other SDKs. This is something we could formalize while working on that topic.

3. What’s the general process for getting mentorship for GSoC? I'd appreciate any guidance on how to get started.

I don't know if we've been formally accepted as a GSoC project yet.

@viccuad can you help with this point since you have more experience with the whole process? thanks!

[viccuad]

@esosaoh you are ahead of the curve :), thanks for showing interest!
The mentoring organizations are announced on February 27th, and applications open March 24th, we need to wait a bit.
Once applications open and we are selected, you will find us in the list of organizations (possibly under CNCF) in https://summerofcode.withgoogle.com.

[BHAVISHYA2005]

@viccuad @flavio 🫡

[esosaoh]

@viccuad GSoC organizations have been announced and CNCF is listed among them. Does this mean that Kubewarden has been selected as a participating project for this year's program?

[viccuad]

@esosaoh yes, we are selected, you can submit your application in https://summerofcode.withgoogle.com, under the "CNCF" organization. The deadline is the 8th of April.

[esosaoh]

@viccuad Thanks for the reminder. I've submitted my application.

[Manpreets59]

Why am am getting this error while submitting my application for gsoc

[viccuad]

@Manpreets59 it may be that you were out of the deadline of 8th of April, 18:00 UTC. We don't administer the page, so this should have needed to be asked on the GsoC contact channels.

[viccuad]

Closing as done!
https://www.kubewarden.io/blog/2025/11/policy-sdk-js/

Congratulations @esosaoh! 😊