diff options
Diffstat (limited to '')
| -rw-r--r-- | vendor/tracing-subscriber/src/layer/mod.rs (renamed from vendor/tracing-subscriber-0.3.3/src/layer/mod.rs) | 820 |
1 files changed, 713 insertions, 107 deletions
diff --git a/vendor/tracing-subscriber-0.3.3/src/layer/mod.rs b/vendor/tracing-subscriber/src/layer/mod.rs index f3f994490..bdc154301 100644 --- a/vendor/tracing-subscriber-0.3.3/src/layer/mod.rs +++ b/vendor/tracing-subscriber/src/layer/mod.rs @@ -19,7 +19,7 @@ //! [`Subscriber`] behavior; it can _observe_ events and spans, but does not //! assign IDs. //! -//! ## Composing Layers +//! # Composing Layers //! //! Since a [`Layer`] does not implement a complete strategy for collecting //! traces, it must be composed with a `Subscriber` in order to be used. The @@ -135,9 +135,245 @@ //! [`Layer::with_subscriber`] as an implementation detail, as `with_subscriber` //! calls must be nested, leading to less clear code for the reader. //! +//! ## Runtime Configuration With `Layer`s +//! +//! In some cases, a particular [`Layer`] may be enabled or disabled based on +//! runtime configuration. This can introduce challenges, because the type of a +//! layered [`Subscriber`] depends on which layers are added to it: if an `if` +//! or `match` expression adds some [`Layer`] implementation in one branch, +//! and other layers in another, the [`Subscriber`] values returned by those +//! branches will have different types. For example, the following _will not_ +//! work: +//! +//! ```compile_fail +//! # fn docs() -> Result<(), Box<dyn std::error::Error + 'static>> { +//! # struct Config { +//! # is_prod: bool, +//! # path: &'static str, +//! # } +//! # let cfg = Config { is_prod: false, path: "debug.log" }; +//! use std::fs::File; +//! use tracing_subscriber::{Registry, prelude::*}; +//! +//! let stdout_log = tracing_subscriber::fmt::layer().pretty(); +//! let subscriber = Registry::default().with(stdout_log); +//! +//! // The compile error will occur here because the if and else +//! // branches have different (and therefore incompatible) types. +//! let subscriber = if cfg.is_prod { +//! let file = File::create(cfg.path)?; +//! let layer = tracing_subscriber::fmt::layer() +//! .json() +//! .with_writer(Arc::new(file)); +//! layer.with(subscriber) +//! } else { +//! layer +//! }; +//! +//! tracing::subscriber::set_global_default(subscriber) +//! .expect("Unable to set global subscriber"); +//! # Ok(()) } +//! ``` +//! +//! However, a [`Layer`] wrapped in an [`Option`] [also implements the `Layer` +//! trait][option-impl]. This allows individual layers to be enabled or disabled at +//! runtime while always producing a [`Subscriber`] of the same type. For +//! example: +//! +//! ``` +//! # fn docs() -> Result<(), Box<dyn std::error::Error + 'static>> { +//! # struct Config { +//! # is_prod: bool, +//! # path: &'static str, +//! # } +//! # let cfg = Config { is_prod: false, path: "debug.log" }; +//! use std::fs::File; +//! use tracing_subscriber::{Registry, prelude::*}; +//! +//! let stdout_log = tracing_subscriber::fmt::layer().pretty(); +//! let subscriber = Registry::default().with(stdout_log); +//! +//! // if `cfg.is_prod` is true, also log JSON-formatted logs to a file. +//! let json_log = if cfg.is_prod { +//! let file = File::create(cfg.path)?; +//! let json_log = tracing_subscriber::fmt::layer() +//! .json() +//! .with_writer(file); +//! Some(json_log) +//! } else { +//! None +//! }; +//! +//! // If `cfg.is_prod` is false, then `json` will be `None`, and this layer +//! // will do nothing. However, the subscriber will still have the same type +//! // regardless of whether the `Option`'s value is `None` or `Some`. +//! let subscriber = subscriber.with(json_log); +//! +//! tracing::subscriber::set_global_default(subscriber) +//! .expect("Unable to set global subscriber"); +//! # Ok(()) } +//! ``` +//! +//! If a [`Layer`] may be one of several different types, note that [`Box<dyn +//! Layer<S> + Send + Sync>` implements `Layer`][box-impl]. +//! This may be used to erase the type of a [`Layer`]. +//! +//! For example, a function that configures a [`Layer`] to log to one of +//! several outputs might return a `Box<dyn Layer<S> + Send + Sync + 'static>`: +//! ``` +//! use tracing_subscriber::{ +//! Layer, +//! registry::LookupSpan, +//! prelude::*, +//! }; +//! use std::{path::PathBuf, fs::File, io}; +//! +//! /// Configures whether logs are emitted to a file, to stdout, or to stderr. +//! pub enum LogConfig { +//! File(PathBuf), +//! Stdout, +//! Stderr, +//! } +//! +//! impl LogConfig { +//! pub fn layer<S>(self) -> Box<dyn Layer<S> + Send + Sync + 'static> +//! where +//! S: tracing_core::Subscriber, +//! for<'a> S: LookupSpan<'a>, +//! { +//! // Shared configuration regardless of where logs are output to. +//! let fmt = tracing_subscriber::fmt::layer() +//! .with_target(true) +//! .with_thread_names(true); +//! +//! // Configure the writer based on the desired log target: +//! match self { +//! LogConfig::File(path) => { +//! let file = File::create(path).expect("failed to create log file"); +//! Box::new(fmt.with_writer(file)) +//! }, +//! LogConfig::Stdout => Box::new(fmt.with_writer(io::stdout)), +//! LogConfig::Stderr => Box::new(fmt.with_writer(io::stderr)), +//! } +//! } +//! } +//! +//! let config = LogConfig::Stdout; +//! tracing_subscriber::registry() +//! .with(config.layer()) +//! .init(); +//! ``` +//! +//! The [`Layer::boxed`] method is provided to make boxing a `Layer` +//! more convenient, but [`Box::new`] may be used as well. +//! +//! When the number of `Layer`s varies at runtime, note that a +//! [`Vec<L> where L: Layer` also implements `Layer`][vec-impl]. This +//! can be used to add a variable number of `Layer`s to a `Subscriber`: +//! +//! ``` +//! use tracing_subscriber::{Layer, prelude::*}; +//! struct MyLayer { +//! // ... +//! } +//! # impl MyLayer { fn new() -> Self { Self {} }} +//! +//! impl<S: tracing_core::Subscriber> Layer<S> for MyLayer { +//! // ... +//! } +//! +//! /// Returns how many layers we need +//! fn how_many_layers() -> usize { +//! // ... +//! # 3 +//! } +//! +//! // Create a variable-length `Vec` of layers +//! let mut layers = Vec::new(); +//! for _ in 0..how_many_layers() { +//! layers.push(MyLayer::new()); +//! } +//! +//! tracing_subscriber::registry() +//! .with(layers) +//! .init(); +//! ``` +//! +//! If a variable number of `Layer` is needed and those `Layer`s have +//! different types, a `Vec` of [boxed `Layer` trait objects][box-impl] may +//! be used. For example: +//! +//! ``` +//! use tracing_subscriber::{filter::LevelFilter, Layer, prelude::*}; +//! use std::fs::File; +//! # fn main() -> Result<(), Box<dyn std::error::Error>> { +//! struct Config { +//! enable_log_file: bool, +//! enable_stdout: bool, +//! enable_stderr: bool, +//! // ... +//! } +//! # impl Config { +//! # fn from_config_file()-> Result<Self, Box<dyn std::error::Error>> { +//! # // don't enable the log file so that the example doesn't actually create it +//! # Ok(Self { enable_log_file: false, enable_stdout: true, enable_stderr: true }) +//! # } +//! # } +//! +//! let cfg = Config::from_config_file()?; +//! +//! // Based on our dynamically loaded config file, create any number of layers: +//! let mut layers = Vec::new(); +//! +//! if cfg.enable_log_file { +//! let file = File::create("myapp.log")?; +//! let layer = tracing_subscriber::fmt::layer() +//! .with_thread_names(true) +//! .with_target(true) +//! .json() +//! .with_writer(file) +//! // Box the layer as a type-erased trait object, so that it can +//! // be pushed to the `Vec`. +//! .boxed(); +//! layers.push(layer); +//! } +//! +//! if cfg.enable_stdout { +//! let layer = tracing_subscriber::fmt::layer() +//! .pretty() +//! .with_filter(LevelFilter::INFO) +//! // Box the layer as a type-erased trait object, so that it can +//! // be pushed to the `Vec`. +//! .boxed(); +//! layers.push(layer); +//! } +//! +//! if cfg.enable_stdout { +//! let layer = tracing_subscriber::fmt::layer() +//! .with_target(false) +//! .with_filter(LevelFilter::WARN) +//! // Box the layer as a type-erased trait object, so that it can +//! // be pushed to the `Vec`. +//! .boxed(); +//! layers.push(layer); +//! } +//! +//! tracing_subscriber::registry() +//! .with(layers) +//! .init(); +//!# Ok(()) } +//! ``` +//! +//! Finally, if the number of layers _changes_ at runtime, a `Vec` of +//! subscribers can be used alongside the [`reload`](crate::reload) module to +//! add or remove subscribers dynamically at runtime. +//! +//! [option-impl]: Layer#impl-Layer<S>-for-Option<L> +//! [box-impl]: Layer#impl-Layer%3CS%3E-for-Box%3Cdyn%20Layer%3CS%3E%20+%20Send%20+%20Sync%3E +//! [vec-impl]: Layer#impl-Layer<S>-for-Vec<L> //! [prelude]: crate::prelude //! -//! ## Recording Traces +//! # Recording Traces //! //! The [`Layer`] trait defines a set of methods for consuming notifications from //! tracing instrumentation, which are generally equivalent to the similarly @@ -146,7 +382,7 @@ //! information provided by the wrapped subscriber (such as [the current span]) //! to the layer. //! -//! ## Filtering with `Layer`s +//! # Filtering with `Layer`s //! //! As well as strategies for handling trace events, the `Layer` trait may also //! be used to represent composable _filters_. This allows the determination of @@ -158,7 +394,7 @@ //! combined with _per-layer filters_ that control what spans and events are //! recorded by those layers. //! -//! ### Global Filtering +//! ## Global Filtering //! //! A `Layer` that implements a filtering strategy should override the //! [`register_callsite`] and/or [`enabled`] methods. It may also choose to implement @@ -179,7 +415,29 @@ //! [`Interest::never()`] from its [`register_callsite`] method, filter //! evaluation will short-circuit and the span or event will be disabled. //! -//! ### Per-Layer Filtering +//! ### Enabling Interest +//! +//! Whenever an tracing event (or span) is emitted, it goes through a number of +//! steps to determine how and how much it should be processed. The earlier an +//! event is disabled, the less work has to be done to process the event, so +//! `Layer`s that implement filtering should attempt to disable unwanted +//! events as early as possible. In order, each event checks: +//! +//! - [`register_callsite`], once per callsite (roughly: once per time that +//! `event!` or `span!` is written in the source code; this is cached at the +//! callsite). See [`Subscriber::register_callsite`] and +//! [`tracing_core::callsite`] for a summary of how this behaves. +//! - [`enabled`], once per emitted event (roughly: once per time that `event!` +//! or `span!` is *executed*), and only if `register_callsite` regesters an +//! [`Interest::sometimes`]. This is the main customization point to globally +//! filter events based on their [`Metadata`]. If an event can be disabled +//! based only on [`Metadata`], it should be, as this allows the construction +//! of the actual `Event`/`Span` to be skipped. +//! - For events only (and not spans), [`event_enabled`] is called just before +//! processing the event. This gives layers one last chance to say that +//! an event should be filtered out, now that the event's fields are known. +//! +//! ## Per-Layer Filtering //! //! **Note**: per-layer filtering APIs currently require the [`"registry"` crate //! feature flag][feat] to be enabled. @@ -393,94 +651,16 @@ //! # Ok(()) } //! ``` //! -//! ## Runtime Configuration With Layers -//! -//! In some cases, a particular [`Layer`] may be enabled or disabled based on -//! runtime configuration. This can introduce challenges, because the type of a -//! layered [`Subscriber`] depends on which layers are added to it: if an `if` -//! or `match` expression adds some [`Layer`]s in one branch and other layers -//! in another, the [`Subscriber`] values returned by those branches will have -//! different types. For example, the following _will not_ work: -//! -//! ```compile_fail -//! # fn docs() -> Result<(), Box<dyn std::error::Error + 'static>> { -//! # struct Config { -//! # is_prod: bool, -//! # path: &'static str, -//! # } -//! # let cfg = Config { is_prod: false, path: "debug.log" }; -//! use std::{fs::File, sync::Arc}; -//! use tracing_subscriber::{Registry, prelude::*}; -//! -//! let stdout_log = tracing_subscriber::fmt::layer().pretty(); -//! let subscriber = Registry::default().with(stdout_log); -//! -//! // The compile error will occur here because the if and else -//! // branches have different (and therefore incompatible) types. -//! let subscriber = if cfg.is_prod { -//! let file = File::create(cfg.path)?; -//! let layer = tracing_subscriber::fmt::layer() -//! .json() -//! .with_writer(Arc::new(file)); -//! subscriber.with(layer) -//! } else { -//! subscriber -//! }; -//! -//! tracing::subscriber::set_global_default(subscriber) -//! .expect("Unable to set global subscriber"); -//! # Ok(()) } -//! ``` -//! -//! However, a [`Layer`] wrapped in an [`Option`] [also implements the `Layer` -//! trait][option-impl]. This allows individual layers to be enabled or disabled at -//! runtime while always producing a [`Subscriber`] of the same type. For -//! example: -//! -//! ``` -//! # fn docs() -> Result<(), Box<dyn std::error::Error + 'static>> { -//! # struct Config { -//! # is_prod: bool, -//! # path: &'static str, -//! # } -//! # let cfg = Config { is_prod: false, path: "debug.log" }; -//! use std::{fs::File, sync::Arc}; -//! use tracing_subscriber::{Registry, prelude::*}; -//! -//! let stdout_log = tracing_subscriber::fmt::layer().pretty(); -//! let subscriber = Registry::default().with(stdout_log); -//! -//! // if `cfg.is_prod` is true, also log JSON-formatted logs to a file. -//! let json_log = if cfg.is_prod { -//! let file = File::create(cfg.path)?; -//! let json_log = tracing_subscriber::fmt::layer() -//! .json() -//! .with_writer(Arc::new(file)); -//! Some(json_log) -//! } else { -//! None -//! }; -//! -//! // If `cfg.is_prod` is false, then `json` will be `None`, and this layer -//! // will do nothing. However, the subscriber will still have the same type -//! // regardless of whether the `Option`'s value is `None` or `Some`. -//! let subscriber = subscriber.with(json_log); -//! -//! tracing::subscriber::set_global_default(subscriber) -//! .expect("Unable to set global subscriber"); -//! # Ok(()) } -//! ``` -//! -//! [`Subscriber`]: https://docs.rs/tracing-core/latest/tracing_core/subscriber/trait.Subscriber.html -//! [span IDs]: https://docs.rs/tracing-core/latest/tracing_core/span/struct.Id.html +//! [`Subscriber`]: tracing_core::subscriber::Subscriber +//! [span IDs]: tracing_core::span::Id //! [the current span]: Context::current_span //! [`register_callsite`]: Layer::register_callsite //! [`enabled`]: Layer::enabled +//! [`event_enabled`]: Layer::event_enabled //! [`on_enter`]: Layer::on_enter //! [`Layer::register_callsite`]: Layer::register_callsite //! [`Layer::enabled`]: Layer::enabled -//! [`Interest::never()`]: https://docs.rs/tracing-core/latest/tracing_core/subscriber/struct.Interest.html#method.never -//! [option-impl]: crate::layer::Layer#impl-Layer<S>-for-Option<L> +//! [`Interest::never()`]: tracing_core::subscriber::Interest::never() //! [`Filtered`]: crate::filter::Filtered //! [`filter`]: crate::filter //! [`Targets`]: crate::filter::Targets @@ -498,7 +678,7 @@ use tracing_core::{ metadata::Metadata, span, subscriber::{Interest, Subscriber}, - Event, LevelFilter, + Dispatch, Event, LevelFilter, }; use core::any::TypeId; @@ -531,6 +711,31 @@ where S: Subscriber, Self: 'static, { + /// Performs late initialization when installing this layer as a + /// [`Subscriber`]. + /// + /// ## Avoiding Memory Leaks + /// + /// `Layer`s should not store the [`Dispatch`] pointing to the [`Subscriber`] + /// that they are a part of. Because the `Dispatch` owns the `Subscriber`, + /// storing the `Dispatch` within the `Subscriber` will create a reference + /// count cycle, preventing the `Dispatch` from ever being dropped. + /// + /// Instead, when it is necessary to store a cyclical reference to the + /// `Dispatch` within a `Layer`, use [`Dispatch::downgrade`] to convert a + /// `Dispatch` into a [`WeakDispatch`]. This type is analogous to + /// [`std::sync::Weak`], and does not create a reference count cycle. A + /// [`WeakDispatch`] can be stored within a subscriber without causing a + /// memory leak, and can be [upgraded] into a `Dispatch` temporarily when + /// the `Dispatch` must be accessed by the subscriber. + /// + /// [`WeakDispatch`]: tracing_core::dispatcher::WeakDispatch + /// [upgraded]: tracing_core::dispatcher::WeakDispatch::upgrade + /// [`Subscriber`]: tracing_core::Subscriber + fn on_register_dispatch(&self, collector: &Dispatch) { + let _ = collector; + } + /// Performs late initialization when attaching a `Layer` to a /// [`Subscriber`]. /// @@ -592,15 +797,15 @@ where /// globally enable or disable those callsites, it should always return /// [`Interest::always()`]. /// - /// [`Interest`]: https://docs.rs/tracing-core/latest/tracing_core/struct.Interest.html - /// [`Subscriber::register_callsite`]: https://docs.rs/tracing-core/latest/tracing_core/trait.Subscriber.html#method.register_callsite - /// [`Interest::never()`]: https://docs.rs/tracing-core/latest/tracing_core/subscriber/struct.Interest.html#method.never - /// [`Interest::always()`]: https://docs.rs/tracing-core/latest/tracing_core/subscriber/struct.Interest.html#method.always - /// [`self.enabled`]: #method.enabled - /// [`Layer::enabled`]: #method.enabled - /// [`on_event`]: #method.on_event - /// [`on_enter`]: #method.on_enter - /// [`on_exit`]: #method.on_exit + /// [`Interest`]: tracing_core::Interest + /// [`Subscriber::register_callsite`]: tracing_core::Subscriber::register_callsite() + /// [`Interest::never()`]: tracing_core::subscriber::Interest::never() + /// [`Interest::always()`]: tracing_core::subscriber::Interest::always() + /// [`self.enabled`]: Layer::enabled() + /// [`Layer::enabled`]: Layer::enabled() + /// [`on_event`]: Layer::on_event() + /// [`on_enter`]: Layer::on_enter() + /// [`on_exit`]: Layer::on_exit() /// [the trait-level documentation]: #filtering-with-layers fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest { if self.enabled(metadata, Context::none()) { @@ -635,13 +840,12 @@ where /// See [the trait-level documentation] for more information on filtering /// with `Layer`s. /// - /// [`Interest`]: https://docs.rs/tracing-core/latest/tracing_core/struct.Interest.html - /// [`Context`]: ../struct.Context.html - /// [`Subscriber::enabled`]: https://docs.rs/tracing-core/latest/tracing_core/trait.Subscriber.html#method.enabled - /// [`Layer::register_callsite`]: #method.register_callsite - /// [`on_event`]: #method.on_event - /// [`on_enter`]: #method.on_enter - /// [`on_exit`]: #method.on_exit + /// [`Interest`]: tracing_core::Interest + /// [`Subscriber::enabled`]: tracing_core::Subscriber::enabled() + /// [`Layer::register_callsite`]: Layer::register_callsite() + /// [`on_event`]: Layer::on_event() + /// [`on_enter`]: Layer::on_enter() + /// [`on_exit`]: Layer::on_exit() /// [the trait-level documentation]: #filtering-with-layers fn enabled(&self, metadata: &Metadata<'_>, ctx: Context<'_, S>) -> bool { let _ = (metadata, ctx); @@ -676,6 +880,31 @@ where // seems like a good future-proofing measure as it may grow other methods later... fn on_follows_from(&self, _span: &span::Id, _follows: &span::Id, _ctx: Context<'_, S>) {} + /// Called before [`on_event`], to determine if `on_event` should be called. + /// + /// <div class="example-wrap" style="display:inline-block"> + /// <pre class="ignore" style="white-space:normal;font:inherit;"> + /// + /// **Note**: This method determines whether an event is globally enabled, + /// *not* whether the individual `Layer` will be notified about the + /// event. This is intended to be used by `Layer`s that implement + /// filtering for the entire stack. `Layer`s which do not wish to be + /// notified about certain events but do not wish to globally disable them + /// should ignore those events in their [on_event][Self::on_event]. + /// + /// </pre></div> + /// + /// See [the trait-level documentation] for more information on filtering + /// with `Layer`s. + /// + /// [`on_event`]: Self::on_event + /// [`Interest`]: tracing_core::Interest + /// [the trait-level documentation]: #filtering-with-layers + #[inline] // collapse this to a constant please mrs optimizer + fn event_enabled(&self, _event: &Event<'_>, _ctx: Context<'_, S>) -> bool { + true + } + /// Notifies this layer that an event has occurred. fn on_event(&self, _event: &Event<'_>, _ctx: Context<'_, S>) {} @@ -840,7 +1069,7 @@ where /// .with_subscriber(MySubscriber::new()); ///``` /// - /// [`Subscriber`]: https://docs.rs/tracing-core/latest/tracing_core/trait.Subscriber.html + /// [`Subscriber`]: tracing_core::Subscriber fn with_subscriber(mut self, mut inner: S) -> Layered<Self, S> where Self: Sized, @@ -857,7 +1086,7 @@ where /// per-layer filtering. /// /// [`Filtered`]: crate::filter::Filtered - /// [plf]: #per-layer-filtering + /// [plf]: crate::layer#per-layer-filtering #[cfg(all(feature = "registry", feature = "std"))] #[cfg_attr(docsrs, doc(cfg(all(feature = "registry", feature = "std"))))] fn with_filter<F>(self, filter: F) -> filter::Filtered<Self, F, S> @@ -868,6 +1097,131 @@ where filter::Filtered::new(self, filter) } + /// Erases the type of this [`Layer`], returning a [`Box`]ed `dyn + /// Layer` trait object. + /// + /// This can be used when a function returns a `Layer` which may be of + /// one of several types, or when a `Layer` subscriber has a very long type + /// signature. + /// + /// # Examples + /// + /// The following example will *not* compile, because the value assigned to + /// `log_layer` may have one of several different types: + /// + /// ```compile_fail + /// # fn main() -> Result<(), Box<dyn std::error::Error>> { + /// use tracing_subscriber::{Layer, filter::LevelFilter, prelude::*}; + /// use std::{path::PathBuf, fs::File, io}; + /// + /// /// Configures whether logs are emitted to a file, to stdout, or to stderr. + /// pub enum LogConfig { + /// File(PathBuf), + /// Stdout, + /// Stderr, + /// } + /// + /// let config = // ... + /// # LogConfig::Stdout; + /// + /// // Depending on the config, construct a layer of one of several types. + /// let log_layer = match config { + /// // If logging to a file, use a maximally-verbose configuration. + /// LogConfig::File(path) => { + /// let file = File::create(path)?; + /// tracing_subscriber::fmt::layer() + /// .with_thread_ids(true) + /// .with_thread_names(true) + /// // Selecting the JSON logging format changes the layer's + /// // type. + /// .json() + /// .with_span_list(true) + /// // Setting the writer to use our log file changes the + /// // layer's type again. + /// .with_writer(file) + /// }, + /// + /// // If logging to stdout, use a pretty, human-readable configuration. + /// LogConfig::Stdout => tracing_subscriber::fmt::layer() + /// // Selecting the "pretty" logging format changes the + /// // layer's type! + /// .pretty() + /// .with_writer(io::stdout) + /// // Add a filter based on the RUST_LOG environment variable; + /// // this changes the type too! + /// .and_then(tracing_subscriber::EnvFilter::from_default_env()), + /// + /// // If logging to stdout, only log errors and warnings. + /// LogConfig::Stderr => tracing_subscriber::fmt::layer() + /// // Changing the writer changes the layer's type + /// .with_writer(io::stderr) + /// // Only log the `WARN` and `ERROR` levels. Adding a filter + /// // changes the layer's type to `Filtered<LevelFilter, ...>`. + /// .with_filter(LevelFilter::WARN), + /// }; + /// + /// tracing_subscriber::registry() + /// .with(log_layer) + /// .init(); + /// # Ok(()) } + /// ``` + /// + /// However, adding a call to `.boxed()` after each match arm erases the + /// layer's type, so this code *does* compile: + /// + /// ``` + /// # fn main() -> Result<(), Box<dyn std::error::Error>> { + /// # use tracing_subscriber::{Layer, filter::LevelFilter, prelude::*}; + /// # use std::{path::PathBuf, fs::File, io}; + /// # pub enum LogConfig { + /// # File(PathBuf), + /// # Stdout, + /// # Stderr, + /// # } + /// # let config = LogConfig::Stdout; + /// let log_layer = match config { + /// LogConfig::File(path) => { + /// let file = File::create(path)?; + /// tracing_subscriber::fmt::layer() + /// .with_thread_ids(true) + /// .with_thread_names(true) + /// .json() + /// .with_span_list(true) + /// .with_writer(file) + /// // Erase the type by boxing the layer + /// .boxed() + /// }, + /// + /// LogConfig::Stdout => tracing_subscriber::fmt::layer() + /// .pretty() + /// .with_writer(io::stdout) + /// .and_then(tracing_subscriber::EnvFilter::from_default_env()) + /// // Erase the type by boxing the layer + /// .boxed(), + /// + /// LogConfig::Stderr => tracing_subscriber::fmt::layer() + /// .with_writer(io::stderr) + /// .with_filter(LevelFilter::WARN) + /// // Erase the type by boxing the layer + /// .boxed(), + /// }; + /// + /// tracing_subscriber::registry() + /// .with(log_layer) + /// .init(); + /// # Ok(()) } + /// ``` + #[cfg(any(feature = "alloc", feature = "std"))] + #[cfg_attr(docsrs, doc(cfg(any(feature = "alloc", feature = "std"))))] + fn boxed(self) -> Box<dyn Layer<S> + Send + Sync + 'static> + where + Self: Sized, + Self: Layer<S> + Send + Sync + 'static, + S: Subscriber, + { + Box::new(self) + } + #[doc(hidden)] unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()> { if id == TypeId::of::<Self>() { @@ -880,6 +1234,7 @@ where feature! { #![all(feature = "registry", feature = "std")] + /// A per-[`Layer`] filter that determines whether a span or event is enabled /// for an individual layer. /// @@ -1022,6 +1377,26 @@ feature! { Interest::sometimes() } + /// Called before the filtered [`Layer]'s [`on_event`], to determine if + /// `on_event` should be called. + /// + /// This gives a chance to filter events based on their fields. Note, + /// however, that this *does not* override [`enabled`], and is not even + /// called if [`enabled`] returns `false`. + /// + /// ## Default Implementation + /// + /// By default, this method returns `true`, indicating that no events are + /// filtered out based on their fields. + /// + /// [`enabled`]: crate::layer::Filter::enabled + /// [`on_event`]: crate::layer::Layer::on_event + #[inline] // collapse this to a constant please mrs optimizer + fn event_enabled(&self, event: &Event<'_>, cx: &Context<'_, S>) -> bool { + let _ = (event, cx); + true + } + /// Returns an optional hint of the highest [verbosity level][level] that /// this `Filter` will enable. /// @@ -1054,6 +1429,51 @@ feature! { fn max_level_hint(&self) -> Option<LevelFilter> { None } + + /// Notifies this filter that a new span was constructed with the given + /// `Attributes` and `Id`. + /// + /// By default, this method does nothing. `Filter` implementations that + /// need to be notified when new spans are created can override this + /// method. + fn on_new_span(&self, attrs: &span::Attributes<'_>, id: &span::Id, ctx: Context<'_, S>) { + let _ = (attrs, id, ctx); + } + + + /// Notifies this filter that a span with the given `Id` recorded the given + /// `values`. + /// + /// By default, this method does nothing. `Filter` implementations that + /// need to be notified when new spans are created can override this + /// method. + fn on_record(&self, id: &span::Id, values: &span::Record<'_>, ctx: Context<'_, S>) { + let _ = (id, values, ctx); + } + + /// Notifies this filter that a span with the given ID was entered. + /// + /// By default, this method does nothing. `Filter` implementations that + /// need to be notified when a span is entered can override this method. + fn on_enter(&self, id: &span::Id, ctx: Context<'_, S>) { + let _ = (id, ctx); + } + + /// Notifies this filter that a span with the given ID was exited. + /// + /// By default, this method does nothing. `Filter` implementations that + /// need to be notified when a span is exited can override this method. + fn on_exit(&self, id: &span::Id, ctx: Context<'_, S>) { + let _ = (id, ctx); + } + + /// Notifies this filter that a span with the given ID has been closed. + /// + /// By default, this method does nothing. `Filter` implementations that + /// need to be notified when a span is closed can override this method. + fn on_close(&self, id: span::Id, ctx: Context<'_, S>) { + let _ = (id, ctx); + } } } @@ -1077,6 +1497,47 @@ pub struct Identity { // === impl Layer === +#[derive(Clone, Copy)] +pub(crate) struct NoneLayerMarker(()); +static NONE_LAYER_MARKER: NoneLayerMarker = NoneLayerMarker(()); + +/// Is a type implementing `Layer` `Option::<_>::None`? +pub(crate) fn layer_is_none<L, S>(layer: &L) -> bool +where + L: Layer<S>, + S: Subscriber, +{ + unsafe { + // Safety: we're not actually *doing* anything with this pointer --- + // this only care about the `Option`, which is essentially being used + // as a bool. We can rely on the pointer being valid, because it is + // a crate-private type, and is only returned by the `Layer` impl + // for `Option`s. However, even if the layer *does* decide to be + // evil and give us an invalid pointer here, that's fine, because we'll + // never actually dereference it. + layer.downcast_raw(TypeId::of::<NoneLayerMarker>()) + } + .is_some() +} + +/// Is a type implementing `Subscriber` `Option::<_>::None`? +pub(crate) fn subscriber_is_none<S>(subscriber: &S) -> bool +where + S: Subscriber, +{ + unsafe { + // Safety: we're not actually *doing* anything with this pointer --- + // this only care about the `Option`, which is essentially being used + // as a bool. We can rely on the pointer being valid, because it is + // a crate-private type, and is only returned by the `Layer` impl + // for `Option`s. However, even if the subscriber *does* decide to be + // evil and give us an invalid pointer here, that's fine, because we'll + // never actually dereference it. + subscriber.downcast_raw(TypeId::of::<NoneLayerMarker>()) + } + .is_some() +} + impl<L, S> Layer<S> for Option<L> where L: Layer<S>, @@ -1115,7 +1576,11 @@ where fn max_level_hint(&self) -> Option<LevelFilter> { match self { Some(ref inner) => inner.max_level_hint(), - None => None, + None => { + // There is no inner layer, so this layer will + // never enable anything. + Some(LevelFilter::OFF) + } } } @@ -1134,6 +1599,14 @@ where } #[inline] + fn event_enabled(&self, event: &Event<'_>, ctx: Context<'_, S>) -> bool { + match self { + Some(ref inner) => inner.event_enabled(event, ctx), + None => true, + } + } + + #[inline] fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>) { if let Some(ref inner) = self { inner.on_event(event, ctx); @@ -1173,6 +1646,8 @@ where unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()> { if id == TypeId::of::<Self>() { Some(self as *const _ as *const ()) + } else if id == TypeId::of::<NoneLayerMarker>() && self.is_none() { + Some(&NONE_LAYER_MARKER as *const _ as *const ()) } else { self.as_ref().and_then(|inner| inner.downcast_raw(id)) } @@ -1181,10 +1656,17 @@ where feature! { #![any(feature = "std", feature = "alloc")] + #[cfg(not(feature = "std"))] + use alloc::vec::Vec; macro_rules! layer_impl_body { () => { #[inline] + fn on_register_dispatch(&self, subscriber: &Dispatch) { + self.deref().on_register_dispatch(subscriber); + } + + #[inline] fn on_layer(&mut self, subscriber: &mut S) { self.deref_mut().on_layer(subscriber); } @@ -1220,6 +1702,11 @@ feature! { } #[inline] + fn event_enabled(&self, event: &Event<'_>, ctx: Context<'_, S>) -> bool { + self.deref().event_enabled(event, ctx) + } + + #[inline] fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>) { self.deref().on_event(event, ctx) } @@ -1266,6 +1753,125 @@ feature! { { layer_impl_body! {} } + + + + impl<S, L> Layer<S> for Vec<L> + where + L: Layer<S>, + S: Subscriber, + { + + fn on_layer(&mut self, subscriber: &mut S) { + for l in self { + l.on_layer(subscriber); + } + } + + fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest { + // Return highest level of interest. + let mut interest = Interest::never(); + for l in self { + let new_interest = l.register_callsite(metadata); + if (interest.is_sometimes() && new_interest.is_always()) + || (interest.is_never() && !new_interest.is_never()) + { + interest = new_interest; + } + } + + interest + } + + fn enabled(&self, metadata: &Metadata<'_>, ctx: Context<'_, S>) -> bool { + self.iter().all(|l| l.enabled(metadata, ctx.clone())) + } + + fn event_enabled(&self, event: &Event<'_>, ctx: Context<'_, S>) -> bool { + self.iter().all(|l| l.event_enabled(event, ctx.clone())) + } + + fn on_new_span(&self, attrs: &span::Attributes<'_>, id: &span::Id, ctx: Context<'_, S>) { + for l in self { + l.on_new_span(attrs, id, ctx.clone()); + } + } + + fn max_level_hint(&self) -> Option<LevelFilter> { + // Default to `OFF` if there are no inner layers. + let mut max_level = LevelFilter::OFF; + for l in self { + // NOTE(eliza): this is slightly subtle: if *any* layer + // returns `None`, we have to return `None`, assuming there is + // no max level hint, since that particular layer cannot + // provide a hint. + let hint = l.max_level_hint()?; + max_level = core::cmp::max(hint, max_level); + } + Some(max_level) + } + + fn on_record(&self, span: &span::Id, values: &span::Record<'_>, ctx: Context<'_, S>) { + for l in self { + l.on_record(span, values, ctx.clone()) + } + } + + fn on_follows_from(&self, span: &span::Id, follows: &span::Id, ctx: Context<'_, S>) { + for l in self { + l.on_follows_from(span, follows, ctx.clone()); + } + } + + fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>) { + for l in self { + l.on_event(event, ctx.clone()); + } + } + + fn on_enter(&self, id: &span::Id, ctx: Context<'_, S>) { + for l in self { + l.on_enter(id, ctx.clone()); + } + } + + fn on_exit(&self, id: &span::Id, ctx: Context<'_, S>) { + for l in self { + l.on_exit(id, ctx.clone()); + } + } + + fn on_close(&self, id: span::Id, ctx: Context<'_, S>) { + for l in self { + l.on_close(id.clone(), ctx.clone()); + } + } + + #[doc(hidden)] + unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()> { + // If downcasting to `Self`, return a pointer to `self`. + if id == TypeId::of::<Self>() { + return Some(self as *const _ as *const ()); + } + + // Someone is looking for per-layer filters. But, this `Vec` + // might contain layers with per-layer filters *and* + // layers without filters. It should only be treated as a + // per-layer-filtered layer if *all* its layers have + // per-layer filters. + // XXX(eliza): it's a bummer we have to do this linear search every + // time. It would be nice if this could be cached, but that would + // require replacing the `Vec` impl with an impl for a newtype... + if filter::is_plf_downcast_marker(id) && self.iter().any(|s| s.downcast_raw(id).is_none()) { + return None; + } + + // Otherwise, return the first child of `self` that downcaasts to + // the selected type, if any. + // XXX(eliza): hope this is reasonable lol + self.iter().find_map(|l| l.downcast_raw(id)) + } + } } // === impl SubscriberExt === |