Is there a way to set a field before insert/update op using a hook or something ?

If you refer to something like feathersjs no, but since you're writing everything, before/after doing the operation you can do whatever you'd like. Example:

myCreateOperation = async (...) => {
    // Before code
    const result = await prisma.createOperation(...)
    //After code
    return result;
}

That’s what I was going to do, but with prisma, there is a lot of places where a node can be updated / created, e.g. in nested queries... I’m thinking of using a middleware but not sure if it’s the right way

Queries aren't updating/creating nodes, only Mutations are capable of doing it. I don't think that there are any side-effects in Mutations. PS: Maybe I don't get your point do...

oops I meant nested mutations

Ohhh.. Got it know, something like this

createUser = async (..) => {
    // Before
    await prisma.createUser({
        ...
        posts: create({
            ....
        })
    })
    // After
}

I was thinking of this https://www.prisma.io/docs/prisma-graphql-api/mutations-qwe2/#upserting-nodes

If you want you can create posts async, with

//Before and //After

hooks, return the ids, and on create user, you can connect the returned ids.

it would be a nothmare to cover all the cases one by one, so I guess middlewares are my best options...

🙂 Yes

Thank you for helping anyway !

No problem!