[Feature]: Add option to automatically externalize dependencies (similar to Rslib’s autoExternal)

[Karibash]

What problem does this feature solve?

Currently, all dependencies are bundled by default. However, some packages break when they are bundled in Node.js applications. For example, Sentry and OpenTelemetry auto-instrumentation rely on being loaded as external dependencies and will not function correctly if bundled.
To address this, we need an option to automatically externalize dependencies instead of bundling them.

What does the proposed API look like?

Introduce an option similar to Rslib’s autoExternal, which automatically marks dependencies as external and excludes them from the bundle.
This would allow developers to build Node.js applications without unintentionally breaking packages that require being externalized.

[chenjiahan]

I know there's a popular package in the webpack community for automatically configuring Node.js externals: https://www.npmjs.com/package/webpack-node-externals

You might want to give this package a try. If it doesn't work well with Rspack, we could consider implementing a similar package specifically for Rspack.

[Karibash]

Thanks for the suggestion! Yes, I’m aware of the webpack-node-externals package, and I believe it could also work with Rsbuild.

That said, what I see as one of the big differences with Rsbuild compared to Rspack is that it allows developers to start a project with very little configuration (please correct me if I’m wrong here).
Since externalizing dependencies for Node.js applications is a very common need, I think providing an option for this out of the box would align well with Rsbuild’s philosophy of sensible defaults and reducing boilerplate.

What do you think?

[Karibash]

By the way, I do have one question: while using Rslib with autoExternal can indeed address this need, is it actually intended to be used for building Node.js applications?
Since the docs clearly state that Rslib is designed for building libraries, I was wondering if relying on it for application builds would be considered outside its intended scope.

Would love to hear your thoughts on whether this usage is “officially supported” or more of a workaround.

[chenjiahan]

Yes, Rslib is designed for building libraries. Although it was not originally intended for this purpose, it can also be used to build some Node.js applications.

For Rsbuild, I will consider adding a similar option to autoExternal, but this requires further research.

[Karibash]

Got it, thanks for clarifying. That makes sense about Rslib’s original purpose. I think having an option like autoExternal in Rsbuild would be very valuable—it would cover a common use case while keeping with the goal of sensible defaults. Looking forward to seeing how this develops.