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A Gopher Meets a Crab

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Re: A Gopher Meets a Crab

#2

Post by joshka »

The weird-looking Rust isn’t really Rust being weird, it’s the type telling the truth.

   Result>, Elapsed>
That’s three independent “not the happy path” channels: timeout, stream closed, and websocket error.

The nicer version is not a cleverer match. It’s choosing a domain error shape and converting into it one layer at a time:

    let timed = tokio::time::timeout(duration, receiver.next()).await;
    let next = timed.map_err(|_| ReceiveError::Timeout)?;
    let item = next.ok_or(ReceiveError::Closed)?;
    let msg = item.map_err(ReceiveError::WebSocket)?;
The ugly line is what happens when you have not decided where to normalize the shape yet.

Re: A Gopher Meets a Crab

#3

Post by loeg »

joshka wrote: post #2

The weird-looking Rust isn’t really Rust being weird, it’s the type telling the truth. Result >, Elapsed> That’s three independent “not the happy path” channels: timeout, stream closed, and websocket error. The nicer version is not a cleverer match. It’s choosing a domain error shape and converting into it one layer at a time: let timed = tokio::time::timeout(duration, receiver.next()).await; let next = timed.map_err…

  Result
Is pretty weird, though, no? Why would you want a unit value / error type?

Re: A Gopher Meets a Crab

#5

Post by tancop »

joshka wrote: post #2

The weird-looking Rust isn’t really Rust being weird, it’s the type telling the truth. Result >, Elapsed> That’s three independent “not the happy path” channels: timeout, stream closed, and websocket error. The nicer version is not a cleverer match. It’s choosing a domain error shape and converting into it one layer at a time: let timed = tokio::time::timeout(duration, receiver.next()).await; let next = timed.map_err…

[dead]

Re: A Gopher Meets a Crab

#6

Post by tux3 »

loeg wrote: post #3
joshka wrote: post #2

The weird-looking Rust isn’t really Rust being weird, it’s the type telling the truth. Result >, Elapsed> That’s three independent “not the happy path” channels: timeout, stream closed, and websocket error. The nicer version is not a cleverer match. It’s choosing a domain error shape and converting into it one layer at a time: let timed = tokio::time::timeout(duration, receiver.next()).await; let next = timed.map_err…

Result Is pretty weird, though, no? Why would you want a unit value / error type?

Sometimes you just want a fancy boolean. The advantage is that Result has all the Result APIs and you can compose it with other Results, but otherwise this is just a success bool.

Re: A Gopher Meets a Crab

#7

Post by MrJohz »

loeg wrote: post #3
joshka wrote: post #2

The weird-looking Rust isn’t really Rust being weird, it’s the type telling the truth. Result >, Elapsed> That’s three independent “not the happy path” channels: timeout, stream closed, and websocket error. The nicer version is not a cleverer match. It’s choosing a domain error shape and converting into it one layer at a time: let timed = tokio::time::timeout(duration, receiver.next()).await; let next = timed.map_err…

Result Is pretty weird, though, no? Why would you want a unit value / error type?

It's basically doing the same thing that, say, `return true` might do to indicate a function succeeded, but with more explicit types. However, because it uses `Result`, it can be used with the `try`/question mark operator which can be convenient in some situations.

That said, a couple of the examples here feel a bit strange - they're clever things you can do, but they're not necessarily things you often have to do, particularly for a relatively simple task like this. I think the problem with the author's approach is that they can't distinguish between "weird because Rust is weird" and "weird because the LLM generated bad code", because they (understandably) don't have enough experience in what good Rust code looks like.

Re: A Gopher Meets a Crab

#8

Post by stingraycharles »

loeg wrote: post #3
joshka wrote: post #2

The weird-looking Rust isn’t really Rust being weird, it’s the type telling the truth. Result >, Elapsed> That’s three independent “not the happy path” channels: timeout, stream closed, and websocket error. The nicer version is not a cleverer match. It’s choosing a domain error shape and converting into it one layer at a time: let timed = tokio::time::timeout(duration, receiver.next()).await; let next = timed.map_err…

Result Is pretty weird, though, no? Why would you want a unit value / error type?

It’s the equivalent of Haskell’s Either, with Option being the equivalent of Maybe. They’re fairly well-defined idioms.
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