Launch fairings are now fallible and take the place of attach fairings,
but they are only run, as the name implies, at launch time.
This is is a fundamental shift from eager execution of set-up routines,
including the now defunct attach fairings, to lazy execution,
precipitated by the transition to `async`. The previous functionality,
while simple, caused grave issues:
1. A instance of 'Rocket' with async attach fairings requires an async
runtime to be constructed.
2. The instance is accessible in non-async contexts.
3. The async attach fairings have no runtime in which to be run.
Here's an example:
```rust
let rocket = rocket::ignite()
.attach(AttachFairing::from(|rocket| async {
Ok(rocket.manage(load_from_network::<T>().await))
}));
let state = rocket.state::<T>();
```
This had no real meaning previously yet was accepted by running the
attach fairing future in an isolated runtime. In isolation, this causes
no issue, but when attach fairing futures share reactor state with other
futures in Rocket, panics ensue.
The new Rocket application lifecycle is this:
* Build - A Rocket instance is constructed. No fairings are run.
* Ignition - All launch fairings are run.
* Liftoff - If all launch fairings succeeded, the server is started.
New 'liftoff' fairings are run in this third phase.
Catchers can now be scoped to paths, with preference given to the
longest-prefix, then the status code. This a breaking change for all
applications that register catchers:
* `Rocket::register()` takes a base path to scope catchers under.
- The previous behavior is recovered with `::register("/", ...)`.
* Catchers now fallibly, instead of silently, collide.
* `ErrorKind::Collision` is now `ErrorKind::Collisions`.
Related changes:
* `Origin` implements `TryFrom<String>`, `TryFrom<&str>`.
* All URI variants implement `TryFrom<Uri>`.
* Added `Segments::prefix_of()`.
* `Rocket::mount()` takes a `TryInto<Origin<'_>>` instead of `&str`
for the base mount point.
* Extended `errors` example with scoped catchers.
* Added scoped sections to catchers guide.
Internal changes:
* Moved router code to `router/router.rs`.
The new benchmarks use routes from real-world project. This is much more
realistic than the previous benchmarks.
The new benchmarks use `criterion` and exist in their own Cargo project.
This surfaced a dormant concurrency related issue. Prior to this commit,
the router used `routed_segments()` to retrieve the path segments of the
request. This was okay as there was no route in the request, and matched
segments were retrieved eagerly.
This commit makes segment matching lazy, so no matching occurs if
unnecessary. Between two matches, a `route` is atomically set of
`Request`. This is now visible in `routed_segments()`, which should not
have considered the current route in the first place. This was fixed.
While offering some utility, the lifetime did not carry its weight, and
in practice offered no further ability to borrow. This greatly
simplifies request guard implementations.
Previously, an `rx` lock was held for the entirety of the check period,
effectively making request handling serial. The implementation also held
a `write` lock to templating context while an expensive user-callback
was called, limiting template-related concurrency during that period.
This was changed so no lock is held during that period and a write-lock
is held only for the duration of the context field write.
Sergio Benitez
Jonah Brüchert
Ben Sully
Abdullah Alyan