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Diffstat (limited to 'vendor/tracing-core/src/dispatcher.rs')
| -rw-r--r-- | vendor/tracing-core/src/dispatcher.rs | 898 |
1 files changed, 898 insertions, 0 deletions
diff --git a/vendor/tracing-core/src/dispatcher.rs b/vendor/tracing-core/src/dispatcher.rs new file mode 100644 index 000000000..041722c36 --- /dev/null +++ b/vendor/tracing-core/src/dispatcher.rs @@ -0,0 +1,898 @@ +//! 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 +//! ``` +//! +//! <pre class="ignore" style="white-space:normal;font:inherit;"> +//! <strong>Note</strong>:the thread-local scoped dispatcher +//! (<a href="#fn.with_default"><code>with_default</code></a>) requires the +//! Rust standard library. <code>no_std</code> users should use +//! <a href="#fn.set_global_default"><code>set_global_default</code></a> +//! instead. +//! </pre> +//! +//! ## 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. +//! +use crate::{ + callsite, span, + subscriber::{self, NoSubscriber, Subscriber}, + Event, LevelFilter, Metadata, +}; + +use crate::stdlib::{ + any::Any, + fmt, + sync::{ + atomic::{AtomicBool, AtomicUsize, Ordering}, + Arc, + }, +}; + +#[cfg(feature = "std")] +use crate::stdlib::{ + cell::{Cell, RefCell, RefMut}, + error, + sync::Weak, +}; + +/// `Dispatch` trace data to a [`Subscriber`]. +/// +#[derive(Clone)] +pub struct Dispatch { + subscriber: Arc<dyn Subscriber + Send + Sync>, +} + +#[cfg(feature = "std")] +thread_local! { + static CURRENT_STATE: State = State { + default: RefCell::new(None), + can_enter: Cell::new(true), + }; +} + +static EXISTS: AtomicBool = AtomicBool::new(false); +static GLOBAL_INIT: AtomicUsize = AtomicUsize::new(UNINITIALIZED); + +const UNINITIALIZED: usize = 0; +const INITIALIZING: usize = 1; +const INITIALIZED: usize = 2; + +static mut GLOBAL_DISPATCH: Option<Dispatch> = None; + +/// The dispatch state of a thread. +#[cfg(feature = "std")] +struct State { + /// This thread's current default dispatcher. + default: RefCell<Option<Dispatch>>, + /// Whether or not we can currently begin dispatching a trace event. + /// + /// This is set to `false` when functions such as `enter`, `exit`, `event`, + /// and `new_span` are called on this thread's default dispatcher, to + /// prevent further trace events triggered inside those functions from + /// creating an infinite recursion. When we finish handling a dispatch, this + /// is set back to `true`. + can_enter: Cell<bool>, +} + +/// While this guard is active, additional calls to subscriber functions on +/// the default dispatcher will not be able to access the dispatch context. +/// Dropping the guard will allow the dispatch context to be re-entered. +#[cfg(feature = "std")] +struct Entered<'a>(&'a State); + +/// A guard that resets the current default dispatcher to the prior +/// default dispatcher when dropped. +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +#[derive(Debug)] +pub struct DefaultGuard(Option<Dispatch>); + +/// Sets this dispatch as the default for the duration of a closure. +/// +/// The default dispatcher is used when creating a new [span] or +/// [`Event`]. +/// +/// <pre class="ignore" style="white-space:normal;font:inherit;"> +/// <strong>Note</strong>: This function required the Rust standard library. +/// <code>no_std</code> users should use <a href="../fn.set_global_default.html"> +/// <code>set_global_default</code></a> instead. +/// </pre> +/// +/// [span]: super::span +/// [`Subscriber`]: super::subscriber::Subscriber +/// [`Event`]: super::event::Event +/// [`set_global_default`]: super::set_global_default +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +pub fn with_default<T>(dispatcher: &Dispatch, f: impl FnOnce() -> T) -> T { + // When this guard is dropped, the default dispatcher will be reset to the + // prior default. Using this (rather than simply resetting after calling + // `f`) ensures that we always reset to the prior dispatcher even if `f` + // panics. + let _guard = set_default(dispatcher); + f() +} + +/// Sets the dispatch as the default dispatch for the duration of the lifetime +/// of the returned DefaultGuard +/// +/// <pre class="ignore" style="white-space:normal;font:inherit;"> +/// <strong>Note</strong>: This function required the Rust standard library. +/// <code>no_std</code> users should use <a href="../fn.set_global_default.html"> +/// <code>set_global_default</code></a> instead. +/// </pre> +/// +/// [`set_global_default`]: super::set_global_default +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +#[must_use = "Dropping the guard unregisters the dispatcher."] +pub fn set_default(dispatcher: &Dispatch) -> DefaultGuard { + // When this guard is dropped, the default dispatcher will be reset to the + // prior default. Using this ensures that we always reset to the prior + // dispatcher even if the thread calling this function panics. + State::set_default(dispatcher.clone()) +} + +/// Sets this dispatch as the global default for the duration of the entire program. +/// Will be used as a fallback if no thread-local dispatch has been set in a thread +/// (using `with_default`.) +/// +/// Can only be set once; subsequent attempts to set the global default will fail. +/// Returns `Err` if the global default has already been set. +/// +/// <div class="example-wrap" style="display:inline-block"><pre class="compile_fail" style="white-space:normal;font:inherit;"> +/// <strong>Warning</strong>: In general, libraries should <em>not</em> call +/// <code>set_global_default()</code>! Doing so will cause conflicts when +/// executables that depend on the library try to set the default later. +/// </pre></div> +/// +/// [span]: super::span +/// [`Subscriber`]: super::subscriber::Subscriber +/// [`Event`]: super::event::Event +pub fn set_global_default(dispatcher: Dispatch) -> Result<(), SetGlobalDefaultError> { + // if `compare_exchange` returns Result::Ok(_), then `new` has been set and + // `current`—now the prior value—has been returned in the `Ok()` branch. + if GLOBAL_INIT + .compare_exchange( + UNINITIALIZED, + INITIALIZING, + Ordering::SeqCst, + Ordering::SeqCst, + ) + .is_ok() + { + unsafe { + GLOBAL_DISPATCH = Some(dispatcher); + } + GLOBAL_INIT.store(INITIALIZED, Ordering::SeqCst); + EXISTS.store(true, Ordering::Release); + Ok(()) + } else { + Err(SetGlobalDefaultError { _no_construct: () }) + } +} + +/// Returns true if a `tracing` dispatcher has ever been set. +/// +/// This may be used to completely elide trace points if tracing is not in use +/// at all or has yet to be initialized. +#[doc(hidden)] +#[inline(always)] +pub fn has_been_set() -> bool { + EXISTS.load(Ordering::Relaxed) +} + +/// Returned if setting the global dispatcher fails. +#[derive(Debug)] +pub struct SetGlobalDefaultError { + _no_construct: (), +} + +impl fmt::Display for SetGlobalDefaultError { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.pad("a global default trace dispatcher has already been set") + } +} + +#[cfg(feature = "std")] +#[cfg_attr(docsrs, doc(cfg(feature = "std")))] +impl error::Error for SetGlobalDefaultError {} + +/// Executes a closure with a reference to this thread's current [dispatcher]. +/// +/// Note that calls to `get_default` should not be nested; if this function is +/// called while inside of another `get_default`, that closure will be provided +/// with `Dispatch::none` rather than the previously set dispatcher. +/// +/// [dispatcher]: super::dispatcher::Dispatch +#[cfg(feature = "std")] +pub fn get_default<T, F>(mut f: F) -> T +where + F: FnMut(&Dispatch) -> T, +{ + CURRENT_STATE + .try_with(|state| { + if let Some(entered) = state.enter() { + return f(&*entered.current()); + } + + f(&Dispatch::none()) + }) + .unwrap_or_else(|_| f(&Dispatch::none())) +} + +/// Executes a closure with a reference to this thread's current [dispatcher]. +/// +/// Note that calls to `get_default` should not be nested; if this function is +/// called while inside of another `get_default`, that closure will be provided +/// with `Dispatch::none` rather than the previously set dispatcher. +/// +/// [dispatcher]: super::dispatcher::Dispatch +#[cfg(feature = "std")] +#[doc(hidden)] +#[inline(never)] +pub fn get_current<T>(f: impl FnOnce(&Dispatch) -> T) -> Option<T> { + CURRENT_STATE + .try_with(|state| { + let entered = state.enter()?; + Some(f(&*entered.current())) + }) + .ok()? +} + +/// Executes a closure with a reference to the current [dispatcher]. +/// +/// [dispatcher]: super::dispatcher::Dispatch +#[cfg(not(feature = "std"))] +#[doc(hidden)] +pub fn get_current<T>(f: impl FnOnce(&Dispatch) -> T) -> Option<T> { + let dispatch = get_global()?; + Some(f(&dispatch)) +} + +/// Executes a closure with a reference to the current [dispatcher]. +/// +/// [dispatcher]: super::dispatcher::Dispatch +#[cfg(not(feature = "std"))] +pub fn get_default<T, F>(mut f: F) -> T +where + F: FnMut(&Dispatch) -> T, +{ + if let Some(d) = get_global() { + f(d) + } else { + f(&Dispatch::none()) + } +} + +fn get_global() -> Option<&'static Dispatch> { + if GLOBAL_INIT.load(Ordering::SeqCst) != INITIALIZED { + return None; + } + unsafe { + // This is safe given the invariant that setting the global dispatcher + // also sets `GLOBAL_INIT` to `INITIALIZED`. + Some(GLOBAL_DISPATCH.as_ref().expect( + "invariant violated: GLOBAL_DISPATCH must be initialized before GLOBAL_INIT is set", + )) + } +} + +#[cfg(feature = "std")] +pub(crate) struct Registrar(Weak<dyn Subscriber + Send + Sync>); + +impl Dispatch { + /// Returns a new `Dispatch` that discards events and spans. + #[inline] + pub fn none() -> Self { + Dispatch { + subscriber: Arc::new(NoSubscriber::default()), + } + } + + /// Returns a `Dispatch` that forwards to the given [`Subscriber`]. + /// + /// [`Subscriber`]: super::subscriber::Subscriber + pub fn new<S>(subscriber: S) -> Self + where + S: Subscriber + Send + Sync + 'static, + { + let me = Dispatch { + subscriber: Arc::new(subscriber), + }; + callsite::register_dispatch(&me); + me + } + + #[cfg(feature = "std")] + pub(crate) fn registrar(&self) -> Registrar { + Registrar(Arc::downgrade(&self.subscriber)) + } + + /// Registers a new callsite with this subscriber, returning whether or not + /// the subscriber is interested in being notified about the callsite. + /// + /// This calls the [`register_callsite`] function on the [`Subscriber`] + /// that this `Dispatch` forwards to. + /// + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`register_callsite`]: super::subscriber::Subscriber::register_callsite + #[inline] + pub fn register_callsite(&self, metadata: &'static Metadata<'static>) -> subscriber::Interest { + self.subscriber.register_callsite(metadata) + } + + /// Returns the highest [verbosity level][level] that this [`Subscriber`] will + /// enable, or `None`, if the subscriber does not implement level-based + /// filtering or chooses not to implement this method. + /// + /// This calls the [`max_level_hint`] function on the [`Subscriber`] + /// that this `Dispatch` forwards to. + /// + /// [level]: super::Level + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`register_callsite`]: super::subscriber::Subscriber::max_level_hint + // TODO(eliza): consider making this a public API? + #[inline] + pub(crate) fn max_level_hint(&self) -> Option<LevelFilter> { + self.subscriber.max_level_hint() + } + + /// Record the construction of a new span, returning a new [ID] for the + /// span being constructed. + /// + /// This calls the [`new_span`] function on the [`Subscriber`] that this + /// `Dispatch` forwards to. + /// + /// [ID]: super::span::Id + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`new_span`]: super::subscriber::Subscriber::new_span + #[inline] + pub fn new_span(&self, span: &span::Attributes<'_>) -> span::Id { + self.subscriber.new_span(span) + } + + /// Record a set of values on a span. + /// + /// This calls the [`record`] function on the [`Subscriber`] that this + /// `Dispatch` forwards to. + /// + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`record`]: super::subscriber::Subscriber::record + #[inline] + pub fn record(&self, span: &span::Id, values: &span::Record<'_>) { + self.subscriber.record(span, values) + } + + /// Adds an indication that `span` follows from the span with the id + /// `follows`. + /// + /// This calls the [`record_follows_from`] function on the [`Subscriber`] + /// that this `Dispatch` forwards to. + /// + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`record_follows_from`]: super::subscriber::Subscriber::record_follows_from + #[inline] + pub fn record_follows_from(&self, span: &span::Id, follows: &span::Id) { + self.subscriber.record_follows_from(span, follows) + } + + /// Returns true if a span with the specified [metadata] would be + /// recorded. + /// + /// This calls the [`enabled`] function on the [`Subscriber`] that this + /// `Dispatch` forwards to. + /// + /// [metadata]: super::metadata::Metadata + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`enabled`]: super::subscriber::Subscriber::enabled + #[inline] + pub fn enabled(&self, metadata: &Metadata<'_>) -> bool { + self.subscriber.enabled(metadata) + } + + /// Records that an [`Event`] has occurred. + /// + /// This calls the [`event`] function on the [`Subscriber`] that this + /// `Dispatch` forwards to. + /// + /// [`Event`]: super::event::Event + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`event`]: super::subscriber::Subscriber::event + #[inline] + pub fn event(&self, event: &Event<'_>) { + if self.subscriber.event_enabled(event) { + self.subscriber.event(event); + } + } + + /// Records that a span has been can_enter. + /// + /// This calls the [`enter`] function on the [`Subscriber`] that this + /// `Dispatch` forwards to. + /// + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`enter`]: super::subscriber::Subscriber::enter + pub fn enter(&self, span: &span::Id) { + self.subscriber.enter(span); + } + + /// Records that a span has been exited. + /// + /// This calls the [`exit`] function on the [`Subscriber`] that this + /// `Dispatch` forwards to. + /// + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`exit`]: super::subscriber::Subscriber::exit + pub fn exit(&self, span: &span::Id) { + self.subscriber.exit(span); + } + + /// Notifies the subscriber that a [span ID] has been cloned. + /// + /// This function must only be called with span IDs that were returned by + /// this `Dispatch`'s [`new_span`] function. The `tracing` crate upholds + /// this guarantee and any other libraries implementing instrumentation APIs + /// must as well. + /// + /// This calls the [`clone_span`] function on the `Subscriber` that this + /// `Dispatch` forwards to. + /// + /// [span ID]: super::span::Id + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`clone_span`]: super::subscriber::Subscriber::clone_span + /// [`new_span`]: super::subscriber::Subscriber::new_span + #[inline] + pub fn clone_span(&self, id: &span::Id) -> span::Id { + self.subscriber.clone_span(id) + } + + /// Notifies the subscriber that a [span ID] has been dropped. + /// + /// This function must only be called with span IDs that were returned by + /// this `Dispatch`'s [`new_span`] function. The `tracing` crate upholds + /// this guarantee and any other libraries implementing instrumentation APIs + /// must as well. + /// + /// This calls the [`drop_span`] function on the [`Subscriber`] that this + /// `Dispatch` forwards to. + /// + /// <pre class="compile_fail" style="white-space:normal;font:inherit;"> + /// <strong>Deprecated</strong>: The <a href="#method.try_close"><code> + /// try_close</code></a> method is functionally identical, but returns + /// <code>true</code> if the span is now closed. It should be used + /// instead of this method. + /// </pre> + /// + /// [span ID]: super::span::Id + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`drop_span`]: super::subscriber::Subscriber::drop_span + /// [`new_span`]: super::subscriber::Subscriber::new_span + /// [`try_close`]: Entered::try_close() + #[inline] + #[deprecated(since = "0.1.2", note = "use `Dispatch::try_close` instead")] + pub fn drop_span(&self, id: span::Id) { + #[allow(deprecated)] + self.subscriber.drop_span(id); + } + + /// Notifies the subscriber that a [span ID] has been dropped, and returns + /// `true` if there are now 0 IDs referring to that span. + /// + /// This function must only be called with span IDs that were returned by + /// this `Dispatch`'s [`new_span`] function. The `tracing` crate upholds + /// this guarantee and any other libraries implementing instrumentation APIs + /// must as well. + /// + /// This calls the [`try_close`] function on the [`Subscriber`] that this + /// `Dispatch` forwards to. + /// + /// [span ID]: super::span::Id + /// [`Subscriber`]: super::subscriber::Subscriber + /// [`try_close`]: super::subscriber::Subscriber::try_close + /// [`new_span`]: super::subscriber::Subscriber::new_span + pub fn try_close(&self, id: span::Id) -> bool { + self.subscriber.try_close(id) + } + + /// Returns a type representing this subscriber's view of the current span. + /// + /// This calls the [`current`] function on the `Subscriber` that this + /// `Dispatch` forwards to. + /// + /// [`current`]: super::subscriber::Subscriber::current_span + #[inline] + pub fn current_span(&self) -> span::Current { + self.subscriber.current_span() + } + + /// Returns `true` if this `Dispatch` forwards to a `Subscriber` of type + /// `T`. + #[inline] + pub fn is<T: Any>(&self) -> bool { + <dyn Subscriber>::is::<T>(&*self.subscriber) + } + + /// Returns some reference to the `Subscriber` this `Dispatch` forwards to + /// if it is of type `T`, or `None` if it isn't. + #[inline] + pub fn downcast_ref<T: Any>(&self) -> Option<&T> { + <dyn Subscriber>::downcast_ref(&*self.subscriber) + } +} + +impl Default for Dispatch { + /// Returns the current default dispatcher + fn default() -> Self { + get_default(|default| default.clone()) + } +} + +impl fmt::Debug for Dispatch { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_tuple("Dispatch") + .field(&format_args!("{:p}", self.subscriber)) + .finish() + } +} + +impl<S> From<S> for Dispatch +where + S: Subscriber + Send + Sync + 'static, +{ + #[inline] + fn from(subscriber: S) -> Self { + Dispatch::new(subscriber) + } +} + +#[cfg(feature = "std")] +impl Registrar { + pub(crate) fn upgrade(&self) -> Option<Dispatch> { + self.0.upgrade().map(|subscriber| Dispatch { subscriber }) + } +} + +// ===== impl State ===== + +#[cfg(feature = "std")] +impl State { + /// Replaces the current default dispatcher on this thread with the provided + /// dispatcher.Any + /// + /// Dropping the returned `ResetGuard` will reset the default dispatcher to + /// the previous value. + #[inline] + fn set_default(new_dispatch: Dispatch) -> DefaultGuard { + let prior = CURRENT_STATE + .try_with(|state| { + state.can_enter.set(true); + state.default.replace(Some(new_dispatch)) + }) + .ok() + .flatten(); + EXISTS.store(true, Ordering::Release); + DefaultGuard(prior) + } + + #[inline] + fn enter(&self) -> Option<Entered<'_>> { + if self.can_enter.replace(false) { + Some(Entered(self)) + } else { + None + } + } +} + +// ===== impl Entered ===== + +#[cfg(feature = "std")] +impl<'a> Entered<'a> { + #[inline] + fn current(&self) -> RefMut<'a, Dispatch> { + let default = self.0.default.borrow_mut(); + RefMut::map(default, |default| { + default.get_or_insert_with(|| get_global().cloned().unwrap_or_else(Dispatch::none)) + }) + } +} + +#[cfg(feature = "std")] +impl<'a> Drop for Entered<'a> { + #[inline] + fn drop(&mut self) { + self.0.can_enter.set(true); + } +} + +// ===== impl DefaultGuard ===== + +#[cfg(feature = "std")] +impl Drop for DefaultGuard { + #[inline] + fn drop(&mut self) { + // Replace the dispatcher and then drop the old one outside + // of the thread-local context. Dropping the dispatch may + // lead to the drop of a subscriber which, in the process, + // could then also attempt to access the same thread local + // state -- causing a clash. + let prev = CURRENT_STATE.try_with(|state| state.default.replace(self.0.take())); + drop(prev) + } +} + +#[cfg(test)] +mod test { + use super::*; + #[cfg(feature = "std")] + use crate::stdlib::sync::atomic::{AtomicUsize, Ordering}; + use crate::{ + callsite::Callsite, + metadata::{Kind, Level, Metadata}, + subscriber::Interest, + }; + + #[test] + fn dispatch_is() { + let dispatcher = Dispatch::new(NoSubscriber::default()); + assert!(dispatcher.is::<NoSubscriber>()); + } + + #[test] + fn dispatch_downcasts() { + let dispatcher = Dispatch::new(NoSubscriber::default()); + assert!(dispatcher.downcast_ref::<NoSubscriber>().is_some()); + } + + struct TestCallsite; + static TEST_CALLSITE: TestCallsite = TestCallsite; + static TEST_META: Metadata<'static> = metadata! { + name: "test", + target: module_path!(), + level: Level::DEBUG, + fields: &[], + callsite: &TEST_CALLSITE, + kind: Kind::EVENT + }; + + impl Callsite for TestCallsite { + fn set_interest(&self, _: Interest) {} + fn metadata(&self) -> &Metadata<'_> { + &TEST_META + } + } + + #[test] + #[cfg(feature = "std")] + fn events_dont_infinite_loop() { + // This test ensures that an event triggered within a subscriber + // won't cause an infinite loop of events. + struct TestSubscriber; + impl Subscriber for TestSubscriber { + fn enabled(&self, _: &Metadata<'_>) -> bool { + true + } + + fn new_span(&self, _: &span::Attributes<'_>) -> span::Id { + span::Id::from_u64(0xAAAA) + } + + fn record(&self, _: &span::Id, _: &span::Record<'_>) {} + + fn record_follows_from(&self, _: &span::Id, _: &span::Id) {} + + fn event(&self, _: &Event<'_>) { + static EVENTS: AtomicUsize = AtomicUsize::new(0); + assert_eq!( + EVENTS.fetch_add(1, Ordering::Relaxed), + 0, + "event method called twice!" + ); + Event::dispatch(&TEST_META, &TEST_META.fields().value_set(&[])) + } + + fn enter(&self, _: &span::Id) {} + + fn exit(&self, _: &span::Id) {} + } + + with_default(&Dispatch::new(TestSubscriber), || { + Event::dispatch(&TEST_META, &TEST_META.fields().value_set(&[])) + }) + } + + #[test] + #[cfg(feature = "std")] + fn spans_dont_infinite_loop() { + // This test ensures that a span created within a subscriber + // won't cause an infinite loop of new spans. + + fn mk_span() { + get_default(|current| { + current.new_span(&span::Attributes::new( + &TEST_META, + &TEST_META.fields().value_set(&[]), + )) + }); + } + + struct TestSubscriber; + impl Subscriber for TestSubscriber { + fn enabled(&self, _: &Metadata<'_>) -> bool { + true + } + + fn new_span(&self, _: &span::Attributes<'_>) -> span::Id { + static NEW_SPANS: AtomicUsize = AtomicUsize::new(0); + assert_eq!( + NEW_SPANS.fetch_add(1, Ordering::Relaxed), + 0, + "new_span method called twice!" + ); + mk_span(); + span::Id::from_u64(0xAAAA) + } + + fn record(&self, _: &span::Id, _: &span::Record<'_>) {} + + fn record_follows_from(&self, _: &span::Id, _: &span::Id) {} + + fn event(&self, _: &Event<'_>) {} + + fn enter(&self, _: &span::Id) {} + + fn exit(&self, _: &span::Id) {} + } + + with_default(&Dispatch::new(TestSubscriber), mk_span) + } + + #[test] + fn default_no_subscriber() { + let default_dispatcher = Dispatch::default(); + assert!(default_dispatcher.is::<NoSubscriber>()); + } + + #[cfg(feature = "std")] + #[test] + fn default_dispatch() { + struct TestSubscriber; + impl Subscriber for TestSubscriber { + fn enabled(&self, _: &Metadata<'_>) -> bool { + true + } + + fn new_span(&self, _: &span::Attributes<'_>) -> span::Id { + span::Id::from_u64(0xAAAA) + } + + fn record(&self, _: &span::Id, _: &span::Record<'_>) {} + + fn record_follows_from(&self, _: &span::Id, _: &span::Id) {} + + fn event(&self, _: &Event<'_>) {} + + fn enter(&self, _: &span::Id) {} + + fn exit(&self, _: &span::Id) {} + } + let guard = set_default(&Dispatch::new(TestSubscriber)); + let default_dispatcher = Dispatch::default(); + assert!(default_dispatcher.is::<TestSubscriber>()); + + drop(guard); + let default_dispatcher = Dispatch::default(); + assert!(default_dispatcher.is::<NoSubscriber>()); + } +} |