Proxied data structures and mobx

[TruePath]

I'm working on a project where I have need of a sorted array type data structure which I'm planning to implement using a balanced binary tree with order statistic (basically binary search tree with some extra info to allow accessing the n-th element). Now, I'd like to allow this structure to be accessed like a normal array which means that I'll need to create a proxy to intercept object access. As I know that mobx also uses proxies internally (when it can) to implement some of it's functionality I'm wondering if I need to be aware/careful of anything to avoid breaking mobx when I use proxies.

Also, regarding performance, I was planning to create a bunch of atoms so that, e.g., an insertion in position 500 only ends up forcing recomputation of observations that look at positions above 500. I'm wondering how worried I should be about the performance impacts of using so many atoms. Is there a good rule of thumb for how many elements each atom should manage (e.g. one atom per 10 fields or something)?

Thanks!

[urugator]

I'm wondering if I need to be aware/careful of anything to avoid breaking mobx when I use proxies.

The mobx will treat it as regular array, so you will have to explicitely instruct mobx not to make it observable (observable.ref), or wrap it in some class (but that's what you're probably trying to avoid by using proxy). EDIT: You could define $mobx symbol on that array, and mobx should treat it as already observable: https://github.com/mobxjs/mobx/blob/main/packages/mobx/src/api/isobservable.ts#L28 (and therefore exlude it from auto conversion)
If you're asking whether mobx proxy will work with already proxied array, I think it will depend on whether or how the proxy modifies the array behavior - if it behaves like regular array, hopefully it should work, but it's not explicitely supported, there are no tests for this afaik.

I'm wondering how worried I should be about the performance impacts of using so many atoms.

I think you can get a good picture by testing this with an observable object or Map. The most heavy lifting probably happens here:
https://github.com/mobxjs/mobx/blob/main/packages/mobx/src/core/derivation.ts#L205-L268
this is at the end of reaction, where it has to diff a list of new and old observables to find what should be (un)observed.