Overview

[Outcome<S, M, F>][Outcome] is an augmentation of the [Result] type found in the Rust standard library.

It is an enum with the variants - [Success(S)], representing success and containing a value - [Mistake(M)], representing an optionally retryable error and containing a value - [Failure(F)], representing failure and containing a value.

rust enum Outcome<S, M, F> { Success(S), Mistake(M), Failure(F), }

[Outcome] is an augmentation to [Result]. It adds a third state to the "success or failure" dichotomy that [Result<T, E>][Result] models. This third state is that of a soft or retryable error. A retryable error is one where an operation might not have succeeded, either due to other operations (e.g., a disk read or write not completing), misconfiguration (e.g., forgetting to set a specific flag before calling a function), or busy resources (e.g., attempting to lock an audio, video, or database resource).

```rust use outcome::prelude::*;

[derive(Debug, PartialEq)]

enum Version { V1, V2 }

[derive(Debug, PartialEq)]

struct EmptyInput;

fn parseversion(header: &[u8]) -> Outcome { match header.get(0) { None => Mistake(EmptyInput), Some(&1) => Success(Version::V1), Some(&2) => Success(Version::V2), Some() => Failure("invalid or unknown version"), } }

let version = parseversion(&[]); asserteq!(version, Mistake(EmptyInput)); ```

Usage

At this time, the name outcome is already taken on [crates.io]. As [crates.io] does not yet support namespaces or collections, we've had to take a unique approach to still publish the crate. To do this, we've generated a UUIDv5 string via python:

python from uuid import * print(uuid5(uuid5(NAMESPACE_DNS, "occult.work"), "outcome"))

This should generate the string 46f94afc-026f-5511-9d7e-7d1fd495fb5c. Thus the dependency in your Cargo.toml will look something like:

toml [dependencies] outcome-46f94afc-026f-5511-9d7e-7d1fd495fb5c = "*"

However, the exported library is still named outcome, so importing it is treated the same:

rust use outcome::prelude::*;

Users can also work around this by using the package key in their dependency declaration:

toml [dependencies.outcome] version = "*" package = "outcome-46f94afc-026f-5511-9d7e-7d1fd495fb5c"

Is this solution friendly to users? No, but neither is the lack of namespacing nor a squatting policy on [crates.io]. If/when this problem is resolved, this crate's documentation (and name!) will be changed and all versions will be yanked.