Comment by iknowstuff
21 hours ago
Rust does not have three error systems. It has one: the Error trait. io::Error is one of many that implement it (nothing special about it). Errors defined via thiserror also implement it.
“Anyhow” just allows you to conveniently say “some Error” if you don’t care to write out an API contract specifying types of errors your function might spit out.
He's not making that up; in practice, you're going to run into and need to make mental space for the idiosyncrasies of multiple error frameworks.
Not sure what you mean by that. If you're consuming the API of a crate that has functions that return errors, you're not really dealing with a "framework", you're just dealing with whatever the `E` is in the `Result<T, E>`. If that `E` doesn't implement std::error::Error, I'd consider that a deficiency (even a bug) for that crate. (Yes, I know some crates want to support use in `no_std` environments; that's what features are for.)
If I care about the specific variants of error that a function can return, so I can do different things depending on what kind of error occurred, I'll read the docs and match. That's not really a "framework" thing; that's just a basic thing that anyone has to do in any language in order to consume an API. If I need to propagate the error, I'll do so (either directly, or by wrapping it in a variant of my own error type). I don't see how any of this is "framework"-y.
A crate's decision to use thiserror (or not) does not matter to me. If a crate exposes `anyhow::Error`, that's a lazy choice and bad API design, but still "works" and I generally don't need to care about it.
Or is there something else you meant when you said "error frameworks"?
Just wanted to add that `Error` has been in core since `1.81` [1], meaning that even `no_std` environments can/should represent errors the same way.
[1] https://doc.rust-lang.org/core/error/trait.Error.html
I guess you might have to if you need to use a library someone's written that doesn't implement the standard.
Writing primarily applications, I couldn't tell you what error handling frameworks my dependencies are using: I literally don't know, and haven't needed to know in order to display, fail, or succeed.
EDIT to add: I use anyhow for this, so I should also add "add context to an error when I fall" to the list of things I do.
What's the standard? I'm not being snarky; I'm going down the thought process of how this would work in practice.
I am on team Io Error [on std rust]", somewhat arbitrarily. If I call a lib that is on Team Anyhow, or Team Custom Error Enum, I will have to do some (Straightfoward, but a little clumsy) conversions if I want ? to work. This is complicated by being able to impl From<ErrorType1> for ErrorType2 only in one direction if you don't control the other crate. (due to the orphan rule)
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Not rust specific, and most certainly not a criticism of you - but I hate when people call a lib that errors, then just bubble that error up.
I mean the error is supposed to be tailored to the audience - I guess what you are saying is that you handle the error by saying "I called foo with X, Y, Z, and got this error back" in the logs - which your caller then also does - producing a log message of
ERROR: I called Foo with X Y and Z and got error: Die MF die
followed by
ERROR: I called Bar with X Y Z and a and got error: ERROR: I called Foo with X Y and Z and got error: Die MF die mf (still fool)
And so on and so forth.
If the counter is - don't log, that's fine, but you have to know where in the call graph that error state was reported to the logs
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