This allows responses to be sent to the client even when data is only
partially read, significantly improving the experience for the client
from one with a "connection closed" error to one with a proper response.
The consequence is a lifetime in 'Data'.
Though other non-lifetime-introducing solutions exist, the introduction
of a lifetime to 'Data' is a longstanding desire as it prevents
smuggling 'Data' into a longer-lived context. Use of 'Data' in that
context was unspecified with various runtime consequences. The addition
of a lifetime bound by the request prevents this error statically.
In summary, the changes are:
* Clients receive responses even when data isn't fully read.
* 'Data' becomes 'Data<'r>'. 'FromData' changes accordingly.
* Route 'Outcome's are strictly tied to the request lifetime.
Tangentially, the invalid length form field validation error message has
improved to format length in byte units if it exceeds 1024.
This commit entirely rewrites Rocket's URI parsing routines and
overhauls the 'uri!' macro resolving all known issues and removing any
potential limitations for compile-time URI creation. This commit:
* Introduces a new 'Reference' URI variant for URI-references.
* Modifies 'Redirect' to accept 'TryFrom<Reference>'.
* Introduces a new 'Asterisk' URI variant for parity.
* Allows creation of any URI type from a string literal via 'uri!'.
* Enables dynamic/static prefixing/suffixing of route URIs in 'uri!'.
* Unifies 'Segments' and 'QuerySegments' into one generic 'Segments'.
* Consolidates URI formatting types/traits into a 'uri::fmt' module.
* Makes APIs more symmetric across URI types.
It also includes the following less-relevant changes:
* Implements 'FromParam' for a single-segment 'PathBuf'.
* Adds 'FileName::is_safe()'.
* No longer reparses upstream request URIs.
Resolves#842.
Resolves#853.
Resolves#998.
This has the following positive effects:
1) The lifetime retrieved through 'Deref' is now long-lived.
2) An '&State<T>` can be created via an '&T'.
3) '&State<T>' is shorter to type than 'State<'_, T>'.
Sentinels resolve a long-standing usability and functional correctness
issue in Rocket: starting an application with guards and/or responders
that depend on state that isn't available. The canonical example is the
'State' guard. Prior to this commit, an application with routes that
queried unmanaged state via 'State' would fail at runtime. With this
commit, the application refuses to launch with a detailed error message.
The 'Sentinel' docs explains it as:
A sentinel, automatically run on ignition, can trigger a launch
abort should an instance fail to meet arbitrary conditions. Every
type that appears in a mounted route's type signature is eligible to
be a sentinel. Of these, those that implement 'Sentinel' have their
'abort()' method invoked automatically, immediately after ignition,
once for each unique type. Sentinels inspect the finalized instance
of 'Rocket' and can trigger a launch abort by returning 'true'.
The following types are now sentinels:
* 'contrib::databases::Connection' (any '#[database]' type)
* 'contrib::templates::Metadata'
* 'contrib::templates::Template'
* 'core::State'
The following are "specialized" sentinels, which allow sentinel
discovery even through type aliases:
* 'Option<T>', 'Debug<T>' if 'T: Sentinel'
* 'Result<T, E>', 'Either<T, E>' if 'T: Sentinel', 'E: Sentinel'
Closes#464.
Sergio Benitez