From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 21:33:14 +0200 Subject: Adding upstream version 115.7.0esr. Signed-off-by: Daniel Baumann --- third_party/rust/tracing/src/dispatcher.rs | 145 +++++++++++++++++++++++++++++ 1 file changed, 145 insertions(+) create mode 100644 third_party/rust/tracing/src/dispatcher.rs (limited to 'third_party/rust/tracing/src/dispatcher.rs') diff --git a/third_party/rust/tracing/src/dispatcher.rs b/third_party/rust/tracing/src/dispatcher.rs new file mode 100644 index 0000000000..a84b99f4eb --- /dev/null +++ b/third_party/rust/tracing/src/dispatcher.rs @@ -0,0 +1,145 @@ +//! Dispatches trace events to [`Subscriber`]s. +//! +//! The _dispatcher_ is the component of the tracing system which is responsible +//! for forwarding trace data from the instrumentation points that generate it +//! to the subscriber that collects it. +//! +//! # Using the Trace Dispatcher +//! +//! Every thread in a program using `tracing` has a _default subscriber_. When +//! events occur, or spans are created, they are dispatched to the thread's +//! current subscriber. +//! +//! ## Setting the Default Subscriber +//! +//! By default, the current subscriber is an empty implementation that does +//! nothing. To use a subscriber implementation, it must be set as the default. +//! There are two methods for doing so: [`with_default`] and +//! [`set_global_default`]. `with_default` sets the default subscriber for the +//! duration of a scope, while `set_global_default` sets a default subscriber +//! for the entire process. +//! +//! To use either of these functions, we must first wrap our subscriber in a +//! [`Dispatch`], a cloneable, type-erased reference to a subscriber. For +//! example: +//! ```rust +//! # pub struct FooSubscriber; +//! # use tracing_core::{ +//! # dispatcher, Event, Metadata, +//! # span::{Attributes, Id, Record} +//! # }; +//! # impl tracing_core::Subscriber for FooSubscriber { +//! # fn new_span(&self, _: &Attributes) -> Id { Id::from_u64(0) } +//! # fn record(&self, _: &Id, _: &Record) {} +//! # fn event(&self, _: &Event) {} +//! # fn record_follows_from(&self, _: &Id, _: &Id) {} +//! # fn enabled(&self, _: &Metadata) -> bool { false } +//! # fn enter(&self, _: &Id) {} +//! # fn exit(&self, _: &Id) {} +//! # } +//! # impl FooSubscriber { fn new() -> Self { FooSubscriber } } +//! use dispatcher::Dispatch; +//! +//! let my_subscriber = FooSubscriber::new(); +//! let my_dispatch = Dispatch::new(my_subscriber); +//! ``` +//! Then, we can use [`with_default`] to set our `Dispatch` as the default for +//! the duration of a block: +//! ```rust +//! # pub struct FooSubscriber; +//! # use tracing_core::{ +//! # dispatcher, Event, Metadata, +//! # span::{Attributes, Id, Record} +//! # }; +//! # impl tracing_core::Subscriber for FooSubscriber { +//! # fn new_span(&self, _: &Attributes) -> Id { Id::from_u64(0) } +//! # fn record(&self, _: &Id, _: &Record) {} +//! # fn event(&self, _: &Event) {} +//! # fn record_follows_from(&self, _: &Id, _: &Id) {} +//! # fn enabled(&self, _: &Metadata) -> bool { false } +//! # fn enter(&self, _: &Id) {} +//! # fn exit(&self, _: &Id) {} +//! # } +//! # impl FooSubscriber { fn new() -> Self { FooSubscriber } } +//! # let my_subscriber = FooSubscriber::new(); +//! # let my_dispatch = dispatcher::Dispatch::new(my_subscriber); +//! // no default subscriber +//! +//! # #[cfg(feature = "std")] +//! dispatcher::with_default(&my_dispatch, || { +//! // my_subscriber is the default +//! }); +//! +//! // no default subscriber again +//! ``` +//! It's important to note that `with_default` will not propagate the current +//! thread's default subscriber to any threads spawned within the `with_default` +//! block. To propagate the default subscriber to new threads, either use +//! `with_default` from the new thread, or use `set_global_default`. +//! +//! As an alternative to `with_default`, we can use [`set_global_default`] to +//! set a `Dispatch` as the default for all threads, for the lifetime of the +//! program. For example: +//! ```rust +//! # pub struct FooSubscriber; +//! # use tracing_core::{ +//! # dispatcher, Event, Metadata, +//! # span::{Attributes, Id, Record} +//! # }; +//! # impl tracing_core::Subscriber for FooSubscriber { +//! # fn new_span(&self, _: &Attributes) -> Id { Id::from_u64(0) } +//! # fn record(&self, _: &Id, _: &Record) {} +//! # fn event(&self, _: &Event) {} +//! # fn record_follows_from(&self, _: &Id, _: &Id) {} +//! # fn enabled(&self, _: &Metadata) -> bool { false } +//! # fn enter(&self, _: &Id) {} +//! # fn exit(&self, _: &Id) {} +//! # } +//! # impl FooSubscriber { fn new() -> Self { FooSubscriber } } +//! # let my_subscriber = FooSubscriber::new(); +//! # let my_dispatch = dispatcher::Dispatch::new(my_subscriber); +//! // no default subscriber +//! +//! dispatcher::set_global_default(my_dispatch) +//! // `set_global_default` will return an error if the global default +//! // subscriber has already been set. +//! .expect("global default was already set!"); +//! +//! // `my_subscriber` is now the default +//! ``` +//! +//! 
+//! Note: The thread-local scoped dispatcher (with_default)
+//! requires the Rust standard library. no_std users should
+//! use set_global_default
+//! instead.
+//!
+//! +//! ## Accessing the Default Subscriber +//! +//! A thread's current default subscriber can be accessed using the +//! [`get_default`] function, which executes a closure with a reference to the +//! currently default `Dispatch`. This is used primarily by `tracing` +//! instrumentation. +//! +//! [`Subscriber`]: crate::Subscriber +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +pub use tracing_core::dispatcher::set_default; +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +pub use tracing_core::dispatcher::with_default; +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +pub use tracing_core::dispatcher::DefaultGuard; +pub use tracing_core::dispatcher::{ + get_default, set_global_default, Dispatch, SetGlobalDefaultError, WeakDispatch, +}; + +/// Private API for internal use by tracing's macros. +/// +/// This function is *not* considered part of `tracing`'s public API, and has no +/// stability guarantees. If you use it, and it breaks or disappears entirely, +/// don't say we didn;'t warn you. +#[doc(hidden)] +pub use tracing_core::dispatcher::has_been_set; -- cgit v1.2.3