Unable to use tauri::command with generic make_handler

[wary rain]

I m trying to use tauri command with make handler. It is generic function that process the aggregate for events and commands. It is coming from OSS project https://github.com/kunjee17/cosmo-store-rs/blob/master/cosmo_store_util/src/aggregate.rs#L16 . It works without any issue for test cases as well as web project where I m using actix. But when I m trying to call via tauri command it is giving issue of send + sync.

I m not getting where I should be looking and what changes I needed to make to make it work with tauri command. Here is the error message

`dyn Aggregate<std::option::Option<Patient>, PatientCommand, PatientEvent>` cannot be shared between threads safely
the trait `Sync` is not implemented for `dyn Aggregate<std::option::Option<Patient>, PatientCommand, PatientEvent>`
required for `&dyn Aggregate<std::option::Option<Patient>, PatientCommand, PatientEvent>` to implement `Send`
required because it captures the following types: `tauri::State<'_, AppState>`, `EventStoreSQLXSqlite`, `Uuid`, `std::string::String`, `PatientCommand`, `std::string::String`, `EventsReadRange<cosmo_store::common::i64_event_version::EventVersion>`, `PatientAggregate`, `impl std::future::Future<Output = Result<Vec<EventRead<PatientEvent, PatientEvent, cosmo_store::common::i64_event_version::EventVersion>>, anyhow::Error>>

Any pointers to even debug this code would be really helpful.

[austere obsidian]

Do you have an example for how this function is used (in a tauri app) too?

just from that error it's not really clear to me what part is not implementing Send or Sync

ah or maybe you just have to tell Rust about it. It may require you to change the function signature to be something like
Removed the code since it wasn't valid rust
i don't know, hard to say for me without seeing the context, especially since i'm not really experienced with traits 🤷

[wary rain]

I did have in private repo. I ll put it on github as well.

@austere obsidian here you go. https://github.com/kunjee17/tauri_es .

And here is function that is giving me the issue. I have just copied from original repo as it was helper function only https://github.com/kunjee17/tauri_es/blob/main/src-tauri/src/patient_helper.rs#L23

[austere obsidian]

i feel like there's no way around using something like a Mutex for at least the store

[wary rain]

@austere obsidian sorry I didn't get it. Mutex for store means ?

[austere obsidian]

Mutex: https://doc.rust-lang.org/std/sync/struct.Mutex.html for interior mutability which basically allows mutation even if it's used across threads.
With store i meant the EventStore argument for make_handler since EventStore uses &mut self internally and i assume that's the error

I'm honestly not sure either, your code uses wayyyy too many traits for me to understand it. (not blaming your code, but my brain lol)

[austere obsidian]

okay i remember after looking at the code again. store.append_events was what takes &mut self so i assumed that's what was causing the issue here but really not sure. I'm not at my best lately when it comes to rust/coding in general.

[wary rain]

But it works without any issue with my web framework as well test cases I wrote.

Thanks for the answer btw. 🙏

[austere obsidian]

Yeah, but those have probably less strict requirements then tauri::command has

I think the main issue here may be the use of tokio's multi threaded runtime so if you make your framework and/or tests use that you may be able to reproduce this issue outside of tauri too