Seems like an interesting effort. A developer is building an alternative Java-based backend to Lemmy's Rust-based one, with the goal of building in a handful of different features. The dev is looking at using this compatibility to migrate their instance over to the new platform, while allowing the community to use their apps of choice.

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[–] mea_rah 1 points 10 months ago

Yeah I suppose ignoring unchecked exceptions, it's pretty similar situation, although the guarantees are a bit stronger in Rust IMO as the fallibility is always in the function signature.

Ergonomically I personally like Result more than exceptions. You can work with it like with any other enum including things like result.ok() which gives you Option. (similar to java Optional I think) There is some syntactic sugar like the ? operator, that will just let you bubble the error up the stack (assuming the return type of the function is also Result) - ie: maybe_do_something()?. But it really is just Enum, so you can do Enum-y things with it:

// similar to try-catch, but you can do this with any Enum
if let Ok(value) = maybe_do_something() {
  println!("Value is {}", value)
}

// Call closure on Ok variant, return 0 if any of the two function fails
let some_number = maybe_number()
  .and_then(|number| process_number_perhaps(number)) // this can also fail
  .unwrap_or(0);

In that sense it's very similar to java's Optional if it could also carry the Exception value and if it was mandatory for any fallible function.

Also (this is besides the point) Result in Rust is just compile-time "zero cost" abstraction. It does not actually compile to any code in the binary. I'm not familiar with Java, but I think at least the unchecked exceptions introduce runtime cost?