Rust API: Expose RecordingStreamError

[kpreid]

Describe the annoyance

My preferred coding style is to never use type aliases for std::result::Result (such as rerun::RecordingStreamResult), but the type RecordingStreamError is private. Rust libraries typically make their error types public even if they also offer a Result.

This lack of public type might also make it impossible to pass the error through some generic error-handling code that required the error type to be named, but I don't have a practical example of that.

Please make RecordingStreamError public (possibly as a struct wrapper if you wish to avoid revealing the enum variants).

Additional context

• rerun 0.9.0

[emilk]

Good catch!

There really should be some compiler setting to catch this mistake 🤔

[kpreid]

There really should be some compiler setting to catch this mistake

https://doc.rust-lang.org/rustc/lints/listing/allowed-by-default.html#unreachable-pub

[kpreid]

Oh, and I could write a PR for this if you like — just let me know whether the enum should be wrapped to be hidden or not as I mentioned above.

[emilk]

unreachable-pub does something else - it checks that everything marked pub is exported from the crate. What I want is that anything marked pub only uses types that are also marked pub

[emilk]

Let's just make RecordingStreamError public. Adding wrappers around everything is very annoying at this early stage in the project. A PR would be very welcome!

[emilk]

I found the bug that prevents rustc from warning about things like this:

• E0446 Doesn't Trigger For Types In Private Modules rust-lang/rust#89264

[kpreid]

unreachable-pub does something else - it checks that everything marked pub is exported from the crate.

unreachable-pub should trigger on this case, because RecordingStreamError is pub but not exported, but it seems that unreachable-pub is counting the type alias as a kind of reachability. (Which I suppose it is if you try hard enough — you can write a trait that lets you extract the error type of a Result as an associated type. But that doesn't seem in the spirit of the thing.) I've filed a Rust issue: rust-lang/rust#116604

What I want is that anything marked pub only uses types that are also marked pub

That rule already exists and is mandatory. If you remove pub from enum RecordingStreamError you get compilation errors.

Let's just make RecordingStreamError public. Adding wrappers around everything is very annoying at this early stage in the project. A PR would be very welcome!

Done: #3786