Any docs and advices/guidance on how to write custom Interceptor/Handlers

[vabatta]

There's very little documentation around it and how they are implemented; in the codebase things are implemented in a few different ways (wrap/unwraphandler, decorator handlers, straight up functions, ...) and it's quite a bit of a barrier given that we will not be sure what/how things will be supported (e.g. #4097).

The overall API also is not really friendly, by having to manually wrap and manually call each wrapped method of the handler in the interceptor dispatch method.

Any guidance and documentation around it would be helpful :)

[Uzlopak]

Yeah, there is currently also no gold standard example

[metcoder95]

I wonder it bringing back the old AbstractHandler could help here.

As @Uzlopak says, there's no best-practice guide or example to use as a baseline.
Nonetheless, if open to contribute, we start building one while guiding you as well so we can keep it for further reference

[Uzlopak]

@metcoder95

What is the simplest interceptor to refactor to gold standard? Maybe we can tackle it, together?

[metcoder95]

Sure!
Either https://github.com/nodejs/undici/blob/main/lib/interceptor/response-error.js
or https://github.com/nodejs/undici/blob/main/lib/interceptor/dump.js are good candidates