mirror of https://github.com/rwf2/Rocket.git
642 lines
20 KiB
Rust
642 lines
20 KiB
Rust
//! Success, failure, and forward handling.
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//!
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//! The `Outcome<S, E, F>` type is similar to the standard library's `Result<S,
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//! E>` type. It is an enum with three variants, each containing a value:
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//! `Success(S)`, which represents a successful outcome, `Failure(E)`, which
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//! represents a failing outcome, and `Forward(F)`, which represents neither a
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//! success or failure, but instead, indicates that processing could not be
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//! handled and should instead be _forwarded_ to whatever can handle the
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//! processing next.
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//!
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//! The `Outcome` type is the return type of many of the core Rocket traits,
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//! including [FromRequest](/rocket/request/trait.FromRequest.html),
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//! [FromData](/rocket/data/trait.FromData.html), and
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//! [Responder](/rocket/response/trait.Responder.html). It is also the return
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//! type of request handlers via the
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//! [Response](/rocket/response/struct.Response.html) type.
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//!
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//! # Success
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//!
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//! A successful `Outcome<S, E, F>`, `Success(S)`, is returned from functions
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//! that complete successfully. The meaning of a `Success` outcome depends on
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//! the context. For instance, the `Outcome` of the `from_data` method of the
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//! `FromData` trait will be matched against the type expected by the user. For
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//! example, consider the following handler:
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//!
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//! ```rust,ignore
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//! #[post("/", data = "<my_val>")]
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//! fn hello(my_val: S) -> ... { }
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//! ```
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//!
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//! The `FromData` implementation for the type `S` returns an `Outcome` with a
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//! `Success(S)`. If `from_data` returns a `Success`, the `Success` value will
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//! be unwrapped and the value will be used as the value of `my_val`.
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//!
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//! # Failure
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//!
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//! A failure `Outcome<S, E, F>`, `Failure(E)`, is returned when a function
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//! fails with some error and no processing can or should continue as a result.
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//! The meaning of a failure depends on the context.
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//!
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//! In Rocket, a `Failure` generally means that a request is taken out of normal
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//! processing. The request is then given to the catcher corresponding to some
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//! status code. Users can catch failures by requesting a type of `Result<S, E>`
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//! or `Option<S>` in request handlers. For example, if a user's handler looks
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//! like:
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//!
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//! ```rust,ignore
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//! #[post("/", data = "<my_val>")]
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//! fn hello(my_val: Result<S, E>) -> ... { }
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//! ```
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//!
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//! The `FromData` implementation for the type `S` returns an `Outcome` with a
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//! `Success(S)` and `Failure(E)`. If `from_data` returns a `Failure`, the
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//! `Failure` value will be unwrapped and the value will be used as the `Err`
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//! value of `my_val` while a `Success` will be unwrapped and used the `Ok`
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//! value.
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//!
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//! # Forward
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//!
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//! A forward `Outcome<S, E, F>`, `Forward(F)`, is returned when a function
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//! wants to indicate that the requested processing should be _forwarded_ to the
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//! next available processor. Again, the exact meaning depends on the context.
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//!
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//! In Rocket, a `Forward` generally means that a request is forwarded to the
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//! next available request handler. For example, consider the following request
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//! handler:
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//!
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//! ```rust,ignore
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//! #[post("/", data = "<my_val>")]
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//! fn hello(my_val: S) -> ... { }
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//! ```
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//!
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//! The `FromData` implementation for the type `S` returns an `Outcome` with a
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//! `Success(S)`, `Failure(E)`, and `Forward(F)`. If the `Outcome` is a
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//! `Forward`, the `hello` handler isn't called. Instead, the incoming request
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//! is forwarded, or passed on to, the next matching route, if any. Ultimately,
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//! if there are no non-forwarding routes, forwarded requests are handled by the
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//! 404 catcher. Similar to `Failure`s, users can catch `Forward`s by requesting
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//! a type of `Option<S>`. If an `Outcome` is a `Forward`, the `Option` will be
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//! `None`.
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use std::fmt;
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use std::ops::Try;
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use yansi::{Paint, Color};
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use self::Outcome::*;
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/// An enum representing success (`Success`), failure (`Failure`), or
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/// forwarding (`Forward`).
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///
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/// See the [top level documentation](/rocket/outcome/) for detailed
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/// information.
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#[must_use]
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#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash)]
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pub enum Outcome<S, E, F> {
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/// Contains the success value.
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Success(S),
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/// Contains the failure error value.
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Failure(E),
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/// Contains the value to forward on.
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Forward(F),
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}
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/// Conversion trait from some type into an Outcome type.
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pub trait IntoOutcome<S, E, F> {
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/// The type to use when returning an `Outcome::Failure`.
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type Failure: Sized;
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/// The type to use when returning an `Outcome::Forward`.
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type Forward: Sized;
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/// Converts `self` into an `Outcome`. If `self` represents a success, an
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/// `Outcome::Success` is returned. Otherwise, an `Outcome::Failure` is
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/// returned with `failure` as the inner value.
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fn into_outcome(self, failure: Self::Failure) -> Outcome<S, E, F>;
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/// Converts `self` into an `Outcome`. If `self` represents a success, an
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/// `Outcome::Success` is returned. Otherwise, an `Outcome::Forward` is
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/// returned with `forward` as the inner value.
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fn or_forward(self, forward: Self::Forward) -> Outcome<S, E, F>;
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}
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impl<S, E, F> IntoOutcome<S, E, F> for Option<S> {
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type Failure = E;
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type Forward = F;
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#[inline]
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fn into_outcome(self, failure: E) -> Outcome<S, E, F> {
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match self {
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Some(val) => Success(val),
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None => Failure(failure)
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}
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}
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#[inline]
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fn or_forward(self, forward: F) -> Outcome<S, E, F> {
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match self {
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Some(val) => Success(val),
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None => Forward(forward)
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}
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}
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}
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impl<S, E, F> Outcome<S, E, F> {
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/// Unwraps the Outcome, yielding the contents of a Success.
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///
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/// # Panics
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///
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/// Panics if the value is not `Success`.
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///
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/// # Examples
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.unwrap(), 10);
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/// ```
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#[inline]
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pub fn unwrap(self) -> S {
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match self {
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Success(val) => val,
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_ => panic!("Expected a successful outcome!")
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}
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}
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/// Unwraps the Outcome, yielding the contents of a Success.
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///
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/// # Panics
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///
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/// If the value is not `Success`, panics with the given `message`.
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///
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/// # Examples
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.expect("success value"), 10);
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/// ```
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#[inline]
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pub fn expect(self, message: &str) -> S {
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match self {
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Success(val) => val,
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_ => panic!("Outcome::expect() failed: {}", message)
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}
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}
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/// Return true if this `Outcome` is a `Success`.
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///
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/// # Examples
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.is_success(), true);
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.is_success(), false);
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///
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/// let x: Outcome<i32, &str, usize> = Forward(25);
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/// assert_eq!(x.is_success(), false);
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/// ```
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#[inline]
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pub fn is_success(&self) -> bool {
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match *self {
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Success(_) => true,
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_ => false
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}
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}
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/// Return true if this `Outcome` is a `Failure`.
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///
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/// # Examples
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.is_failure(), false);
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.is_failure(), true);
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///
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/// let x: Outcome<i32, &str, usize> = Forward(25);
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/// assert_eq!(x.is_failure(), false);
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/// ```
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#[inline]
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pub fn is_failure(&self) -> bool {
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match *self {
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Failure(_) => true,
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_ => false
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}
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}
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/// Return true if this `Outcome` is a `Forward`.
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///
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/// # Examples
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.is_forward(), false);
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.is_forward(), false);
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///
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/// let x: Outcome<i32, &str, usize> = Forward(25);
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/// assert_eq!(x.is_forward(), true);
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/// ```
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#[inline]
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pub fn is_forward(&self) -> bool {
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match *self {
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Forward(_) => true,
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_ => false
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}
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}
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/// Converts from `Outcome<S, E, F>` to `Option<S>`.
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///
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/// Returns the `Some` of the `Success` if this is a `Success`, otherwise
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/// returns `None`. `self` is consumed, and all other values are discarded.
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.succeeded(), Some(10));
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.succeeded(), None);
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///
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/// let x: Outcome<i32, &str, usize> = Forward(25);
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/// assert_eq!(x.succeeded(), None);
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/// ```
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#[inline]
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pub fn succeeded(self) -> Option<S> {
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match self {
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Success(val) => Some(val),
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_ => None
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}
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}
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/// Converts from `Outcome<S, E, F>` to `Option<E>`.
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///
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/// Returns the `Some` of the `Failure` if this is a `Failure`, otherwise
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/// returns `None`. `self` is consumed, and all other values are discarded.
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.failed(), None);
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.failed(), Some("Hi! I'm an error."));
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///
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/// let x: Outcome<i32, &str, usize> = Forward(25);
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/// assert_eq!(x.failed(), None);
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/// ```
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#[inline]
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pub fn failed(self) -> Option<E> {
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match self {
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Failure(val) => Some(val),
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_ => None
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}
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}
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/// Converts from `Outcome<S, E, F>` to `Option<F>`.
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///
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/// Returns the `Some` of the `Forward` if this is a `Forward`, otherwise
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/// returns `None`. `self` is consumed, and all other values are discarded.
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.forwarded(), None);
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.forwarded(), None);
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///
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/// let x: Outcome<i32, &str, usize> = Forward(25);
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/// assert_eq!(x.forwarded(), Some(25));
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/// ```
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#[inline]
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pub fn forwarded(self) -> Option<F> {
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match self {
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Forward(val) => Some(val),
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_ => None
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}
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}
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/// Converts from `Outcome<S, E, F>` to `Result<S, T>` for a given `T`.
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///
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/// Returns `Ok` with the `Success` value if this is a `Success`, otherwise
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/// returns an `Err` with the provided value. `self` is consumed, and all
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/// other values are discarded.
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.success_or(false), Ok(10));
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.success_or(false), Err(false));
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///
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/// let x: Outcome<i32, &str, usize> = Forward(25);
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/// assert_eq!(x.success_or("whoops"), Err("whoops"));
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/// ```
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#[inline]
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pub fn success_or<T>(self, value: T) -> Result<S, T> {
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match self {
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Success(val) => Ok(val),
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_ => Err(value)
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}
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}
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/// Converts from `Outcome<S, E, F>` to `Result<S, T>` for a given `T`
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/// produced from a supplied function or closure.
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///
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/// Returns `Ok` with the `Success` value if this is a `Success`, otherwise
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/// returns an `Err` with the result of calling `f`. `self` is consumed, and
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/// all other values are discarded.
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.success_or_else(|| false), Ok(10));
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.success_or_else(|| false), Err(false));
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///
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/// let x: Outcome<i32, &str, usize> = Forward(25);
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/// assert_eq!(x.success_or_else(|| "whoops"), Err("whoops"));
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/// ```
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#[inline]
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pub fn success_or_else<T, V: FnOnce() -> T>(self, f: V) -> Result<S, T> {
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match self {
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Success(val) => Ok(val),
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_ => Err(f())
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}
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}
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/// Converts from `Outcome<S, E, F>` to `Outcome<&S, &E, &F>`.
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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/// assert_eq!(x.as_ref(), Success(&10));
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///
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/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
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/// assert_eq!(x.as_ref(), Failure(&"Hi! I'm an error."));
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/// ```
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#[inline]
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pub fn as_ref(&self) -> Outcome<&S, &E, &F> {
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match *self {
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Success(ref val) => Success(val),
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Failure(ref val) => Failure(val),
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Forward(ref val) => Forward(val),
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}
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}
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/// Maps an `Outcome<S, E, F>` to an `Outcome<T, E, F>` by applying the
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/// function `f` to the value of type `S` in `self` if `self` is an
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/// `Outcome::Success`.
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Success(10);
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///
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/// let mapped = x.map(|v| if v == 10 { "10" } else { "not 10" });
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/// assert_eq!(mapped, Success("10"));
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/// ```
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#[inline]
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pub fn map<T, M: FnOnce(S) -> T>(self, f: M) -> Outcome<T, E, F> {
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match self {
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Success(val) => Success(f(val)),
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Failure(val) => Failure(val),
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Forward(val) => Forward(val),
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}
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}
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/// Maps an `Outcome<S, E, F>` to an `Outcome<S, T, F>` by applying the
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/// function `f` to the value of type `E` in `self` if `self` is an
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/// `Outcome::Failure`.
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///
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Failure("hi");
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///
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/// let mapped = x.map_failure(|v| if v == "hi" { 10 } else { 0 });
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/// assert_eq!(mapped, Failure(10));
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/// ```
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#[inline]
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pub fn map_failure<T, M: FnOnce(E) -> T>(self, f: M) -> Outcome<S, T, F> {
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match self {
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Success(val) => Success(val),
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Failure(val) => Failure(f(val)),
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Forward(val) => Forward(val),
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}
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}
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/// Maps an `Outcome<S, E, F>` to an `Outcome<S, E, T>` by applying the
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/// function `f` to the value of type `F` in `self` if `self` is an
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/// `Outcome::Forward`.
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///
|
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/// ```rust
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/// # use rocket::outcome::Outcome;
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/// # use rocket::outcome::Outcome::*;
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/// #
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/// let x: Outcome<i32, &str, usize> = Forward(5);
|
|
///
|
|
/// let mapped = x.map_forward(|v| if v == 5 { "a" } else { "b" });
|
|
/// assert_eq!(mapped, Forward("a"));
|
|
/// ```
|
|
#[inline]
|
|
pub fn map_forward<T, M: FnOnce(F) -> T>(self, f: M) -> Outcome<S, E, T> {
|
|
match self {
|
|
Success(val) => Success(val),
|
|
Failure(val) => Failure(val),
|
|
Forward(val) => Forward(f(val)),
|
|
}
|
|
}
|
|
|
|
/// Maps an `Outcome<S, E, F>` to an `Outcome<T, E, F>` by applying the
|
|
/// function `f` to the value of type `S` in `self` if `self` is an
|
|
/// `Outcome::Success`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// # use rocket::outcome::Outcome;
|
|
/// # use rocket::outcome::Outcome::*;
|
|
/// #
|
|
/// let x: Outcome<i32, &str, bool> = Success(10);
|
|
///
|
|
/// let mapped = x.and_then(|v| match v {
|
|
/// 10 => Success("10"),
|
|
/// 1 => Forward(false),
|
|
/// _ => Failure("30")
|
|
/// });
|
|
///
|
|
/// assert_eq!(mapped, Success("10"));
|
|
/// ```
|
|
#[inline]
|
|
pub fn and_then<T, M: FnOnce(S) -> Outcome<T, E, F>>(self, f: M) -> Outcome<T, E, F> {
|
|
match self {
|
|
Success(val) => f(val),
|
|
Failure(val) => Failure(val),
|
|
Forward(val) => Forward(val),
|
|
}
|
|
}
|
|
|
|
/// Maps an `Outcome<S, E, F>` to an `Outcome<S, T, F>` by applying the
|
|
/// function `f` to the value of type `E` in `self` if `self` is an
|
|
/// `Outcome::Failure`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// # use rocket::outcome::Outcome;
|
|
/// # use rocket::outcome::Outcome::*;
|
|
/// #
|
|
/// let x: Outcome<i32, &str, bool> = Failure("hi");
|
|
///
|
|
/// let mapped = x.failure_then(|v| match v {
|
|
/// "hi" => Failure(10),
|
|
/// "test" => Forward(false),
|
|
/// _ => Success(10)
|
|
/// });
|
|
///
|
|
/// assert_eq!(mapped, Failure(10));
|
|
/// ```
|
|
#[inline]
|
|
pub fn failure_then<T, M: FnOnce(E) -> Outcome<S, T, F>>(self, f: M) -> Outcome<S, T, F> {
|
|
match self {
|
|
Success(val) => Success(val),
|
|
Failure(val) => f(val),
|
|
Forward(val) => Forward(val),
|
|
}
|
|
}
|
|
|
|
/// Maps an `Outcome<S, E, F>` to an `Outcome<S, E, T>` by applying the
|
|
/// function `f` to the value of type `F` in `self` if `self` is an
|
|
/// `Outcome::Forward`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// # use rocket::outcome::Outcome;
|
|
/// # use rocket::outcome::Outcome::*;
|
|
/// #
|
|
/// let x: Outcome<i32, &str, Option<bool>> = Forward(Some(false));
|
|
///
|
|
/// let mapped = x.forward_then(|v| match v {
|
|
/// Some(true) => Success(10),
|
|
/// Some(false) => Forward(20),
|
|
/// None => Failure("10")
|
|
/// });
|
|
///
|
|
/// assert_eq!(mapped, Forward(20));
|
|
/// ```
|
|
#[inline]
|
|
pub fn forward_then<T, M: FnOnce(F) -> Outcome<S, E, T>>(self, f: M) -> Outcome<S, E, T> {
|
|
match self {
|
|
Success(val) => Success(val),
|
|
Failure(val) => Failure(val),
|
|
Forward(val) => f(val),
|
|
}
|
|
}
|
|
|
|
/// Converts from `Outcome<S, E, F>` to `Outcome<&mut S, &mut E, &mut F>`.
|
|
///
|
|
/// ```rust
|
|
/// # use rocket::outcome::Outcome;
|
|
/// # use rocket::outcome::Outcome::*;
|
|
/// #
|
|
/// let mut x: Outcome<i32, &str, usize> = Success(10);
|
|
/// if let Success(val) = x.as_mut() {
|
|
/// *val = 20;
|
|
/// }
|
|
///
|
|
/// assert_eq!(x.unwrap(), 20);
|
|
/// ```
|
|
#[inline]
|
|
pub fn as_mut(&mut self) -> Outcome<&mut S, &mut E, &mut F> {
|
|
match *self {
|
|
Success(ref mut val) => Success(val),
|
|
Failure(ref mut val) => Failure(val),
|
|
Forward(ref mut val) => Forward(val),
|
|
}
|
|
}
|
|
|
|
#[inline]
|
|
fn formatting(&self) -> (Color, &'static str) {
|
|
match *self {
|
|
Success(..) => (Color::Green, "Success"),
|
|
Failure(..) => (Color::Red, "Failure"),
|
|
Forward(..) => (Color::Yellow, "Forward"),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<S, E, F> Try for Outcome<S, E, F> {
|
|
type Ok = S;
|
|
type Error = Result<F, E>;
|
|
|
|
fn into_result(self) -> Result<Self::Ok, Self::Error> {
|
|
match self {
|
|
Success(val) => Ok(val),
|
|
Forward(val) => Err(Ok(val)),
|
|
Failure(val) => Err(Err(val)),
|
|
}
|
|
}
|
|
|
|
fn from_error(val: Self::Error) -> Self {
|
|
match val {
|
|
Ok(val) => Forward(val),
|
|
Err(val) => Failure(val),
|
|
}
|
|
}
|
|
|
|
fn from_ok(val: Self::Ok) -> Self {
|
|
Success(val)
|
|
}
|
|
}
|
|
|
|
impl<S, E, F> fmt::Debug for Outcome<S, E, F> {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
write!(f, "Outcome::{}", self.formatting().1)
|
|
}
|
|
}
|
|
|
|
impl<S, E, F> fmt::Display for Outcome<S, E, F> {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
let (color, string) = self.formatting();
|
|
write!(f, "{}", Paint::new(string).fg(color))
|
|
}
|
|
}
|