Returning monads/Result types in controllers

[tbarusseau]

I'm using the effect library, where the Effect type is used to represent a bunch of things, but mainly successes and errors. But for a simpler explanation, imagine I'm returning a type such as this one:

export type Result<T, E = Error> =
  | { ok: true; value: T }
  | { ok: false; error: E };

Ideally I would like to be able to return such values from within my controllers. The strength of this paradigm means that I have very explicit success/failure values, and I can properly handle them everywhere, when it makes sense.

Now, I would like these types to be the ones I return from my controller's functions. This allows my controller's functions to return each time either a success or failure value. If I do it right now, it's completely useless. 1. My Effect needs to be executed (sort of like a Promise would be when awaited). 2. I can't respond to REST requests with JSON data that can contain both success or failure values!

Is there a mechanism that would allow me to centralize the handling of these types? I can see that there is a centralized exception handling, however... This only applies to controllers that throw, where in my case I just return monads (or Result, or Effect types).

Basically, I'm looking for an "outgoing" middleware in AdonisJS... I've read the documentation and guides, but couldn't find anything that matches what I'm describing.

Thanks in advance.

[tbarusseau]

Note that one solution would be to systematically call the same function at the end of every single controller, something that awaits and handles the result based on whether it's a success or a failure. However, this creates a lot of redundancy and manual operations in the code base that I would love to be able to "automagically" hide away using an existing AdonisJS mechanism.

[Julien-R44]

I think middleware should be enough to do what you want. Check this : https://docs.adonisjs.com/guides/basics/middleware#middleware-execution-flow

Basically, anything called after an await next allows you to have the outgoing middleware you were describing

[tbarusseau]

Interesting, I completely missed this part of the middleware documentation! This looks perfect. Thanks a lot.