1//! A `Subscriber` for formatting and logging `tracing` data.
2//!
3//! # Overview
4//!
5//! [`tracing`] is a framework for instrumenting Rust programs with context-aware,
6//! structured, event-based diagnostic information. This crate provides an
7//! implementation of the [`Subscriber`] trait that records `tracing`'s `Event`s
8//! and `Span`s by formatting them as text and logging them to stdout.
9//!
10//! # Usage
11//!
12//! First, add this to your `Cargo.toml` file:
13//!
14//! ```toml
15//! [dependencies]
16//! tracing-subscriber = "0.3"
17//! ```
18//!
19//! *Compiler support: [requires `rustc` 1.63+][msrv]*
20//!
21//! [msrv]: super#supported-rust-versions
22//!
23//! Add the following to your executable to initialize the default subscriber:
24//! ```rust
25//! use tracing_subscriber;
26//!
27//! tracing_subscriber::fmt::init();
28//! ```
29//!
30//! ## Filtering Events with Environment Variables
31//!
32//! The default subscriber installed by `init` enables you to filter events
33//! at runtime using environment variables (using the [`EnvFilter`]).
34//!
35//! The filter syntax is a superset of the [`env_logger`] syntax.
36//!
37//! For example:
38//! - Setting `RUST_LOG=debug` enables all `Span`s and `Event`s
39//! set to the log level `DEBUG` or higher
40//! - Setting `RUST_LOG=my_crate=trace` enables `Span`s and `Event`s
41//! in `my_crate` at all log levels
42//!
43//! **Note**: This should **not** be called by libraries. Libraries should use
44//! [`tracing`] to publish `tracing` `Event`s.
45//!
46//! # Configuration
47//!
48//! You can configure a subscriber instead of using the defaults with
49//! the following functions:
50//!
51//! ### Subscriber
52//!
53//! The [`FmtSubscriber`] formats and records `tracing` events as line-oriented logs.
54//! You can create one by calling:
55//!
56//! ```rust
57//! let subscriber = tracing_subscriber::fmt()
58//! // ... add configuration
59//! .finish();
60//! ```
61//!
62//! You can find the configuration methods for [`FmtSubscriber`] in
63//! [`SubscriberBuilder`].
64//!
65//! ## Formatters
66//!
67//! The output format used by the layer and subscriber in this module is
68//! represented by implementing the [`FormatEvent`] trait, and can be
69//! customized. This module provides a number of formatter implementations:
70//!
71//! * [`format::Full`]: The default formatter. This emits human-readable,
72//! single-line logs for each event that occurs, with the current span context
73//! displayed before the formatted representation of the event. See
74//! [here](format::Full#example-output) for sample output.
75//!
76//! * [`format::Compact`]: A variant of the default formatter, optimized for
77//! short line lengths. Fields from the current span context are appended to
78//! the fields of the formatted event. See
79//! [here](format::Compact#example-output) for sample output.
80//!
81//! * [`format::Pretty`]: Emits excessively pretty, multi-line logs, optimized
82//! for human readability. This is primarily intended to be used in local
83//! development and debugging, or for command-line applications, where
84//! automated analysis and compact storage of logs is less of a priority than
85//! readability and visual appeal. See [here](format::Pretty#example-output)
86//! for sample output.
87//!
88//! * [`format::Json`]: Outputs newline-delimited JSON logs. This is intended
89//! for production use with systems where structured logs are consumed as JSON
90//! by analysis and viewing tools. The JSON output is not optimized for human
91//! readability. See [here](format::Json#example-output) for sample output.
92//!
93//! ### Customizing Formatters
94//!
95//! The formatting of log lines for spans and events is controlled by two
96//! traits, [`FormatEvent`] and [`FormatFields`]. The [`FormatEvent`] trait
97//! determines the overall formatting of the log line, such as what information
98//! from the event's metadata and span context is included and in what order.
99//! The [`FormatFields`] trait determines how fields — both the event's
100//! fields and fields on spans — are formatted.
101//!
102//! The [`fmt::format`] module provides several types which implement these traits,
103//! many of which expose additional configuration options to customize their
104//! output. The [`format::Format`] type implements common configuration used by
105//! all the formatters provided in this crate, and can be used as a builder to
106//! set specific formatting settings. For example:
107//!
108//! ```
109//! use tracing_subscriber::fmt;
110//!
111//! // Configure a custom event formatter
112//! let format = fmt::format()
113//! .with_level(false) // don't include levels in formatted output
114//! .with_target(false) // don't include targets
115//! .with_thread_ids(true) // include the thread ID of the current thread
116//! .with_thread_names(true) // include the name of the current thread
117//! .compact(); // use the `Compact` formatting style.
118//!
119//! // Create a `fmt` subscriber that uses our custom event format, and set it
120//! // as the default.
121//! tracing_subscriber::fmt()
122//! .event_format(format)
123//! .init();
124//! ```
125//!
126//! However, if a specific output format is needed, other crates can
127//! also implement [`FormatEvent`] and [`FormatFields`]. See those traits'
128//! documentation for details on how to implement them.
129//!
130//! ## Filters
131//!
132//! If you want to filter the `tracing` `Events` based on environment
133//! variables, you can use the [`EnvFilter`] as follows:
134//!
135//! ```rust
136//! use tracing_subscriber::EnvFilter;
137//!
138//! let filter = EnvFilter::from_default_env();
139//! ```
140//!
141//! As mentioned above, the [`EnvFilter`] allows `Span`s and `Event`s to
142//! be filtered at runtime by setting the `RUST_LOG` environment variable.
143//!
144//! You can find the other available [`filter`]s in the documentation.
145//!
146//! ### Using Your Subscriber
147//!
148//! Finally, once you have configured your `Subscriber`, you need to
149//! configure your executable to use it.
150//!
151//! A subscriber can be installed globally using:
152//! ```rust
153//! use tracing;
154//! use tracing_subscriber::FmtSubscriber;
155//!
156//! let subscriber = FmtSubscriber::new();
157//!
158//! tracing::subscriber::set_global_default(subscriber)
159//! .map_err(|_err| eprintln!("Unable to set global default subscriber"));
160//! // Note this will only fail if you try to set the global default
161//! // subscriber multiple times
162//! ```
163//!
164//! ### Composing Layers
165//!
166//! Composing an [`EnvFilter`] `Layer` and a [format `Layer`][super::fmt::Layer]:
167//!
168//! ```rust
169//! use tracing_subscriber::{fmt, EnvFilter};
170//! use tracing_subscriber::prelude::*;
171//!
172//! let fmt_layer = fmt::layer()
173//! .with_target(false);
174//! let filter_layer = EnvFilter::try_from_default_env()
175//! .or_else(|_| EnvFilter::try_new("info"))
176//! .unwrap();
177//!
178//! tracing_subscriber::registry()
179//! .with(filter_layer)
180//! .with(fmt_layer)
181//! .init();
182//! ```
183//!
184//! [`EnvFilter`]: super::filter::EnvFilter
185//! [`env_logger`]: https://docs.rs/env_logger/
186//! [`filter`]: super::filter
187//! [`FmtSubscriber`]: Subscriber
188//! [`Subscriber`]:
189//! https://docs.rs/tracing/latest/tracing/trait.Subscriber.html
190//! [`tracing`]: https://crates.io/crates/tracing
191//! [`fmt::format`]: mod@crate::fmt::format
192use std::{any::TypeId, error::Error, io};
193use tracing_core::{span, subscriber::Interest, Event, Metadata};
194
195mod fmt_layer;
196#[cfg_attr(docsrs, doc(cfg(all(feature = "fmt", feature = "std"))))]
197pub mod format;
198#[cfg_attr(docsrs, doc(cfg(all(feature = "fmt", feature = "std"))))]
199pub mod time;
200#[cfg_attr(docsrs, doc(cfg(all(feature = "fmt", feature = "std"))))]
201pub mod writer;
202
203pub use fmt_layer::{FmtContext, FormattedFields, Layer};
204
205use crate::layer::Layer as _;
206use crate::util::SubscriberInitExt;
207use crate::{
208 filter::LevelFilter,
209 layer,
210 registry::{LookupSpan, Registry},
211};
212
213#[doc(inline)]
214pub use self::{
215 format::{format, FormatEvent, FormatFields},
216 time::time,
217 writer::{MakeWriter, TestWriter},
218};
219
220/// A `Subscriber` that logs formatted representations of `tracing` events.
221///
222/// This consists of an inner `Formatter` wrapped in a layer that performs filtering.
223#[cfg_attr(docsrs, doc(cfg(all(feature = "fmt", feature = "std"))))]
224#[derive(Debug)]
225pub struct Subscriber<
226 N = format::DefaultFields,
227 E = format::Format<format::Full>,
228 F = LevelFilter,
229 W = fn() -> io::Stdout,
230> {
231 inner: layer::Layered<F, Formatter<N, E, W>>,
232}
233
234/// A `Subscriber` that logs formatted representations of `tracing` events.
235/// This type only logs formatted events; it does not perform any filtering.
236#[cfg_attr(docsrs, doc(cfg(all(feature = "fmt", feature = "std"))))]
237pub type Formatter<
238 N = format::DefaultFields,
239 E = format::Format<format::Full>,
240 W = fn() -> io::Stdout,
241> = layer::Layered<fmt_layer::Layer<Registry, N, E, W>, Registry>;
242
243/// Configures and constructs `Subscriber`s.
244#[cfg_attr(docsrs, doc(cfg(all(feature = "fmt", feature = "std"))))]
245#[derive(Debug)]
246#[must_use]
247pub struct SubscriberBuilder<
248 N = format::DefaultFields,
249 E = format::Format<format::Full>,
250 F = LevelFilter,
251 W = fn() -> io::Stdout,
252> {
253 filter: F,
254 inner: Layer<Registry, N, E, W>,
255}
256
257/// Returns a new [`SubscriberBuilder`] for configuring a [formatting subscriber].
258///
259/// This is essentially shorthand for [`SubscriberBuilder::default()]`.
260///
261/// # Examples
262///
263/// Using [`init`] to set the default subscriber:
264///
265/// ```rust
266/// tracing_subscriber::fmt().init();
267/// ```
268///
269/// Configuring the output format:
270///
271/// ```rust
272///
273/// tracing_subscriber::fmt()
274/// // Configure formatting settings.
275/// .with_target(false)
276/// .with_timer(tracing_subscriber::fmt::time::uptime())
277/// .with_level(true)
278/// // Set the subscriber as the default.
279/// .init();
280/// ```
281///
282/// [`try_init`] returns an error if the default subscriber could not be set:
283///
284/// ```rust
285/// use std::error::Error;
286///
287/// fn init_subscriber() -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
288/// tracing_subscriber::fmt()
289/// // Configure the subscriber to emit logs in JSON format.
290/// .json()
291/// // Configure the subscriber to flatten event fields in the output JSON objects.
292/// .flatten_event(true)
293/// // Set the subscriber as the default, returning an error if this fails.
294/// .try_init()?;
295///
296/// Ok(())
297/// }
298/// ```
299///
300/// Rather than setting the subscriber as the default, [`finish`] _returns_ the
301/// constructed subscriber, which may then be passed to other functions:
302///
303/// ```rust
304/// let subscriber = tracing_subscriber::fmt()
305/// .with_max_level(tracing::Level::DEBUG)
306/// .compact()
307/// .finish();
308///
309/// tracing::subscriber::with_default(subscriber, || {
310/// // the subscriber will only be set as the default
311/// // inside this closure...
312/// })
313/// ```
314///
315/// [formatting subscriber]: Subscriber
316/// [`SubscriberBuilder::default()`]: SubscriberBuilder::default
317/// [`init`]: SubscriberBuilder::init()
318/// [`try_init`]: SubscriberBuilder::try_init()
319/// [`finish`]: SubscriberBuilder::finish()
320#[cfg_attr(docsrs, doc(cfg(all(feature = "fmt", feature = "std"))))]
321pub fn fmt() -> SubscriberBuilder {
322 SubscriberBuilder::default()
323}
324
325/// Returns a new [formatting layer] that can be [composed] with other layers to
326/// construct a [`Subscriber`].
327///
328/// This is a shorthand for the equivalent [`Layer::default()`] function.
329///
330/// [formatting layer]: Layer
331/// [composed]: crate::layer
332/// [`Layer::default()`]: Layer::default
333#[cfg_attr(docsrs, doc(cfg(all(feature = "fmt", feature = "std"))))]
334pub fn layer<S>() -> Layer<S> {
335 Layer::default()
336}
337
338impl Subscriber {
339 /// The maximum [verbosity level] that is enabled by a `Subscriber` by
340 /// default.
341 ///
342 /// This can be overridden with the [`SubscriberBuilder::with_max_level`] method.
343 ///
344 /// [verbosity level]: tracing_core::Level
345 /// [`SubscriberBuilder::with_max_level`]: SubscriberBuilder::with_max_level
346 pub const DEFAULT_MAX_LEVEL: LevelFilter = LevelFilter::INFO;
347
348 /// Returns a new `SubscriberBuilder` for configuring a format subscriber.
349 pub fn builder() -> SubscriberBuilder {
350 SubscriberBuilder::default()
351 }
352
353 /// Returns a new format subscriber with the default configuration.
354 pub fn new() -> Self {
355 Default::default()
356 }
357}
358
359impl Default for Subscriber {
360 fn default() -> Self {
361 SubscriberBuilder::default().finish()
362 }
363}
364
365// === impl Subscriber ===
366
367impl<N, E, F, W> tracing_core::Subscriber for Subscriber<N, E, F, W>
368where
369 N: for<'writer> FormatFields<'writer> + 'static,
370 E: FormatEvent<Registry, N> + 'static,
371 F: layer::Layer<Formatter<N, E, W>> + 'static,
372 W: for<'writer> MakeWriter<'writer> + 'static,
373 layer::Layered<F, Formatter<N, E, W>>: tracing_core::Subscriber,
374 fmt_layer::Layer<Registry, N, E, W>: layer::Layer<Registry>,
375{
376 #[inline]
377 fn register_callsite(&self, meta: &'static Metadata<'static>) -> Interest {
378 self.inner.register_callsite(meta)
379 }
380
381 #[inline]
382 fn enabled(&self, meta: &Metadata<'_>) -> bool {
383 self.inner.enabled(meta)
384 }
385
386 #[inline]
387 fn new_span(&self, attrs: &span::Attributes<'_>) -> span::Id {
388 self.inner.new_span(attrs)
389 }
390
391 #[inline]
392 fn record(&self, span: &span::Id, values: &span::Record<'_>) {
393 self.inner.record(span, values)
394 }
395
396 #[inline]
397 fn record_follows_from(&self, span: &span::Id, follows: &span::Id) {
398 self.inner.record_follows_from(span, follows)
399 }
400
401 #[inline]
402 fn event_enabled(&self, event: &Event<'_>) -> bool {
403 self.inner.event_enabled(event)
404 }
405
406 #[inline]
407 fn event(&self, event: &Event<'_>) {
408 self.inner.event(event);
409 }
410
411 #[inline]
412 fn enter(&self, id: &span::Id) {
413 // TODO: add on_enter hook
414 self.inner.enter(id);
415 }
416
417 #[inline]
418 fn exit(&self, id: &span::Id) {
419 self.inner.exit(id);
420 }
421
422 #[inline]
423 fn current_span(&self) -> span::Current {
424 self.inner.current_span()
425 }
426
427 #[inline]
428 fn clone_span(&self, id: &span::Id) -> span::Id {
429 self.inner.clone_span(id)
430 }
431
432 #[inline]
433 fn try_close(&self, id: span::Id) -> bool {
434 self.inner.try_close(id)
435 }
436
437 #[inline]
438 fn max_level_hint(&self) -> Option<tracing_core::LevelFilter> {
439 self.inner.max_level_hint()
440 }
441
442 unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()> {
443 if id == TypeId::of::<Self>() {
444 Some(self as *const Self as *const ())
445 } else {
446 self.inner.downcast_raw(id)
447 }
448 }
449}
450
451impl<'a, N, E, F, W> LookupSpan<'a> for Subscriber<N, E, F, W>
452where
453 layer::Layered<F, Formatter<N, E, W>>: LookupSpan<'a>,
454{
455 type Data = <layer::Layered<F, Formatter<N, E, W>> as LookupSpan<'a>>::Data;
456
457 fn span_data(&'a self, id: &span::Id) -> Option<Self::Data> {
458 self.inner.span_data(id)
459 }
460}
461
462// ===== impl SubscriberBuilder =====
463
464impl Default for SubscriberBuilder {
465 fn default() -> Self {
466 SubscriberBuilder {
467 filter: Subscriber::DEFAULT_MAX_LEVEL,
468 inner: Default::default(),
469 }
470 .log_internal_errors(true)
471 }
472}
473
474impl<N, E, F, W> SubscriberBuilder<N, E, F, W>
475where
476 N: for<'writer> FormatFields<'writer> + 'static,
477 E: FormatEvent<Registry, N> + 'static,
478 W: for<'writer> MakeWriter<'writer> + 'static,
479 F: layer::Layer<Formatter<N, E, W>> + Send + Sync + 'static,
480 fmt_layer::Layer<Registry, N, E, W>: layer::Layer<Registry> + Send + Sync + 'static,
481{
482 /// Finish the builder, returning a new `FmtSubscriber`.
483 pub fn finish(self) -> Subscriber<N, E, F, W> {
484 let subscriber = self.inner.with_subscriber(Registry::default());
485 Subscriber {
486 inner: self.filter.with_subscriber(subscriber),
487 }
488 }
489
490 /// Install this Subscriber as the global default if one is
491 /// not already set.
492 ///
493 /// If the `tracing-log` feature is enabled, this will also install
494 /// the LogTracer to convert `Log` records into `tracing` `Event`s.
495 ///
496 /// # Errors
497 /// Returns an Error if the initialization was unsuccessful, likely
498 /// because a global subscriber was already installed by another
499 /// call to `try_init`.
500 pub fn try_init(self) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
501 use crate::util::SubscriberInitExt;
502 self.finish().try_init()?;
503
504 Ok(())
505 }
506
507 /// Install this Subscriber as the global default.
508 ///
509 /// If the `tracing-log` feature is enabled, this will also install
510 /// the LogTracer to convert `Log` records into `tracing` `Event`s.
511 ///
512 /// # Panics
513 /// Panics if the initialization was unsuccessful, likely because a
514 /// global subscriber was already installed by another call to `try_init`.
515 pub fn init(self) {
516 self.try_init()
517 .expect("Unable to install global subscriber")
518 }
519}
520
521impl<N, E, F, W> From<SubscriberBuilder<N, E, F, W>> for tracing_core::Dispatch
522where
523 N: for<'writer> FormatFields<'writer> + 'static,
524 E: FormatEvent<Registry, N> + 'static,
525 W: for<'writer> MakeWriter<'writer> + 'static,
526 F: layer::Layer<Formatter<N, E, W>> + Send + Sync + 'static,
527 fmt_layer::Layer<Registry, N, E, W>: layer::Layer<Registry> + Send + Sync + 'static,
528{
529 fn from(builder: SubscriberBuilder<N, E, F, W>) -> tracing_core::Dispatch {
530 tracing_core::Dispatch::new(builder.finish())
531 }
532}
533
534impl<N, L, T, F, W> SubscriberBuilder<N, format::Format<L, T>, F, W>
535where
536 N: for<'writer> FormatFields<'writer> + 'static,
537{
538 /// Use the given [`timer`] for log message timestamps.
539 ///
540 /// See the [`time` module] for the provided timer implementations.
541 ///
542 /// Note that using the `"time`"" feature flag enables the
543 /// additional time formatters [`UtcTime`] and [`LocalTime`], which use the
544 /// [`time` crate] to provide more sophisticated timestamp formatting
545 /// options.
546 ///
547 /// [`timer`]: time::FormatTime
548 /// [`time` module]: mod@time
549 /// [`UtcTime`]: time::UtcTime
550 /// [`LocalTime`]: time::LocalTime
551 /// [`time` crate]: https://docs.rs/time/0.3
552 pub fn with_timer<T2>(self, timer: T2) -> SubscriberBuilder<N, format::Format<L, T2>, F, W> {
553 SubscriberBuilder {
554 filter: self.filter,
555 inner: self.inner.with_timer(timer),
556 }
557 }
558
559 /// Do not emit timestamps with log messages.
560 pub fn without_time(self) -> SubscriberBuilder<N, format::Format<L, ()>, F, W> {
561 SubscriberBuilder {
562 filter: self.filter,
563 inner: self.inner.without_time(),
564 }
565 }
566
567 /// Configures how synthesized events are emitted at points in the [span
568 /// lifecycle][lifecycle].
569 ///
570 /// The following options are available:
571 ///
572 /// - `FmtSpan::NONE`: No events will be synthesized when spans are
573 /// created, entered, exited, or closed. Data from spans will still be
574 /// included as the context for formatted events. This is the default.
575 /// - `FmtSpan::NEW`: An event will be synthesized when spans are created.
576 /// - `FmtSpan::ENTER`: An event will be synthesized when spans are entered.
577 /// - `FmtSpan::EXIT`: An event will be synthesized when spans are exited.
578 /// - `FmtSpan::CLOSE`: An event will be synthesized when a span closes. If
579 /// [timestamps are enabled][time] for this formatter, the generated
580 /// event will contain fields with the span's _busy time_ (the total
581 /// time for which it was entered) and _idle time_ (the total time that
582 /// the span existed but was not entered).
583 /// - `FmtSpan::ACTIVE`: An event will be synthesized when spans are entered
584 /// or exited.
585 /// - `FmtSpan::FULL`: Events will be synthesized whenever a span is
586 /// created, entered, exited, or closed. If timestamps are enabled, the
587 /// close event will contain the span's busy and idle time, as
588 /// described above.
589 ///
590 /// The options can be enabled in any combination. For instance, the following
591 /// will synthesize events whenever spans are created and closed:
592 ///
593 /// ```rust
594 /// use tracing_subscriber::fmt::format::FmtSpan;
595 /// use tracing_subscriber::fmt;
596 ///
597 /// let subscriber = fmt()
598 /// .with_span_events(FmtSpan::NEW | FmtSpan::CLOSE)
599 /// .finish();
600 /// ```
601 ///
602 /// Note that the generated events will only be part of the log output by
603 /// this formatter; they will not be recorded by other `Subscriber`s or by
604 /// `Layer`s added to this subscriber.
605 ///
606 /// [lifecycle]: https://docs.rs/tracing/latest/tracing/span/index.html#the-span-lifecycle
607 /// [time]: SubscriberBuilder::without_time()
608 pub fn with_span_events(self, kind: format::FmtSpan) -> Self {
609 SubscriberBuilder {
610 inner: self.inner.with_span_events(kind),
611 ..self
612 }
613 }
614
615 /// Sets whether or not the formatter emits ANSI terminal escape codes
616 /// for colors and other text formatting.
617 ///
618 /// Enabling ANSI escapes (calling `with_ansi(true)`) requires the "ansi"
619 /// crate feature flag. Calling `with_ansi(true)` without the "ansi"
620 /// feature flag enabled will panic if debug assertions are enabled, or
621 /// print a warning otherwise.
622 ///
623 /// This method itself is still available without the feature flag. This
624 /// is to allow ANSI escape codes to be explicitly *disabled* without
625 /// having to opt-in to the dependencies required to emit ANSI formatting.
626 /// This way, code which constructs a formatter that should never emit
627 /// ANSI escape codes can ensure that they are not used, regardless of
628 /// whether or not other crates in the dependency graph enable the "ansi"
629 /// feature flag.
630 #[cfg(feature = "ansi")]
631 #[cfg_attr(docsrs, doc(cfg(feature = "ansi")))]
632 pub fn with_ansi(self, ansi: bool) -> SubscriberBuilder<N, format::Format<L, T>, F, W> {
633 SubscriberBuilder {
634 inner: self.inner.with_ansi(ansi),
635 ..self
636 }
637 }
638
639 /// Sets whether to write errors from [`FormatEvent`] to the writer.
640 /// Defaults to true.
641 ///
642 /// By default, `fmt::Layer` will write any `FormatEvent`-internal errors to
643 /// the writer. These errors are unlikely and will only occur if there is a
644 /// bug in the `FormatEvent` implementation or its dependencies.
645 ///
646 /// If writing to the writer fails, the error message is printed to stderr
647 /// as a fallback.
648 ///
649 /// [`FormatEvent`]: crate::fmt::FormatEvent
650 pub fn log_internal_errors(
651 self,
652 log_internal_errors: bool,
653 ) -> SubscriberBuilder<N, format::Format<L, T>, F, W> {
654 SubscriberBuilder {
655 inner: self.inner.log_internal_errors(log_internal_errors),
656 ..self
657 }
658 }
659
660 /// Sets whether or not an event's target is displayed.
661 pub fn with_target(
662 self,
663 display_target: bool,
664 ) -> SubscriberBuilder<N, format::Format<L, T>, F, W> {
665 SubscriberBuilder {
666 inner: self.inner.with_target(display_target),
667 ..self
668 }
669 }
670
671 /// Sets whether or not an event's [source code file path][file] is
672 /// displayed.
673 ///
674 /// [file]: tracing_core::Metadata::file
675 pub fn with_file(
676 self,
677 display_filename: bool,
678 ) -> SubscriberBuilder<N, format::Format<L, T>, F, W> {
679 SubscriberBuilder {
680 inner: self.inner.with_file(display_filename),
681 ..self
682 }
683 }
684
685 /// Sets whether or not an event's [source code line number][line] is
686 /// displayed.
687 ///
688 /// [line]: tracing_core::Metadata::line
689 pub fn with_line_number(
690 self,
691 display_line_number: bool,
692 ) -> SubscriberBuilder<N, format::Format<L, T>, F, W> {
693 SubscriberBuilder {
694 inner: self.inner.with_line_number(display_line_number),
695 ..self
696 }
697 }
698
699 /// Sets whether or not an event's level is displayed.
700 pub fn with_level(
701 self,
702 display_level: bool,
703 ) -> SubscriberBuilder<N, format::Format<L, T>, F, W> {
704 SubscriberBuilder {
705 inner: self.inner.with_level(display_level),
706 ..self
707 }
708 }
709
710 /// Sets whether or not the [name] of the current thread is displayed
711 /// when formatting events.
712 ///
713 /// [name]: std::thread#naming-threads
714 pub fn with_thread_names(
715 self,
716 display_thread_names: bool,
717 ) -> SubscriberBuilder<N, format::Format<L, T>, F, W> {
718 SubscriberBuilder {
719 inner: self.inner.with_thread_names(display_thread_names),
720 ..self
721 }
722 }
723
724 /// Sets whether or not the [thread ID] of the current thread is displayed
725 /// when formatting events.
726 ///
727 /// [thread ID]: std::thread::ThreadId
728 pub fn with_thread_ids(
729 self,
730 display_thread_ids: bool,
731 ) -> SubscriberBuilder<N, format::Format<L, T>, F, W> {
732 SubscriberBuilder {
733 inner: self.inner.with_thread_ids(display_thread_ids),
734 ..self
735 }
736 }
737
738 /// Sets the subscriber being built to use a less verbose formatter.
739 ///
740 /// See [`format::Compact`].
741 pub fn compact(self) -> SubscriberBuilder<N, format::Format<format::Compact, T>, F, W>
742 where
743 N: for<'writer> FormatFields<'writer> + 'static,
744 {
745 SubscriberBuilder {
746 filter: self.filter,
747 inner: self.inner.compact(),
748 }
749 }
750
751 /// Sets the subscriber being built to use an [excessively pretty, human-readable formatter](crate::fmt::format::Pretty).
752 #[cfg(feature = "ansi")]
753 #[cfg_attr(docsrs, doc(cfg(feature = "ansi")))]
754 pub fn pretty(
755 self,
756 ) -> SubscriberBuilder<format::Pretty, format::Format<format::Pretty, T>, F, W> {
757 SubscriberBuilder {
758 filter: self.filter,
759 inner: self.inner.pretty(),
760 }
761 }
762
763 /// Sets the subscriber being built to use a JSON formatter.
764 ///
765 /// See [`format::Json`] for details.
766 #[cfg(feature = "json")]
767 #[cfg_attr(docsrs, doc(cfg(feature = "json")))]
768 pub fn json(
769 self,
770 ) -> SubscriberBuilder<format::JsonFields, format::Format<format::Json, T>, F, W>
771 where
772 N: for<'writer> FormatFields<'writer> + 'static,
773 {
774 SubscriberBuilder {
775 filter: self.filter,
776 inner: self.inner.json(),
777 }
778 }
779}
780
781#[cfg(feature = "json")]
782#[cfg_attr(docsrs, doc(cfg(feature = "json")))]
783impl<T, F, W> SubscriberBuilder<format::JsonFields, format::Format<format::Json, T>, F, W> {
784 /// Sets the json subscriber being built to flatten event metadata.
785 ///
786 /// See [`format::Json`] for details.
787 pub fn flatten_event(
788 self,
789 flatten_event: bool,
790 ) -> SubscriberBuilder<format::JsonFields, format::Format<format::Json, T>, F, W> {
791 SubscriberBuilder {
792 filter: self.filter,
793 inner: self.inner.flatten_event(flatten_event),
794 }
795 }
796
797 /// Sets whether or not the JSON subscriber being built will include the current span
798 /// in formatted events.
799 ///
800 /// See [`format::Json`] for details.
801 pub fn with_current_span(
802 self,
803 display_current_span: bool,
804 ) -> SubscriberBuilder<format::JsonFields, format::Format<format::Json, T>, F, W> {
805 SubscriberBuilder {
806 filter: self.filter,
807 inner: self.inner.with_current_span(display_current_span),
808 }
809 }
810
811 /// Sets whether or not the JSON subscriber being built will include a list (from
812 /// root to leaf) of all currently entered spans in formatted events.
813 ///
814 /// See [`format::Json`] for details.
815 pub fn with_span_list(
816 self,
817 display_span_list: bool,
818 ) -> SubscriberBuilder<format::JsonFields, format::Format<format::Json, T>, F, W> {
819 SubscriberBuilder {
820 filter: self.filter,
821 inner: self.inner.with_span_list(display_span_list),
822 }
823 }
824}
825
826#[cfg(feature = "env-filter")]
827#[cfg_attr(docsrs, doc(cfg(feature = "env-filter")))]
828impl<N, E, W> SubscriberBuilder<N, E, crate::EnvFilter, W>
829where
830 Formatter<N, E, W>: tracing_core::Subscriber + 'static,
831{
832 /// Configures the subscriber being built to allow filter reloading at
833 /// runtime.
834 pub fn with_filter_reloading(
835 self,
836 ) -> SubscriberBuilder<N, E, crate::reload::Layer<crate::EnvFilter, Formatter<N, E, W>>, W>
837 {
838 let (filter, _) = crate::reload::Layer::new(self.filter);
839 SubscriberBuilder {
840 filter,
841 inner: self.inner,
842 }
843 }
844}
845
846#[cfg(feature = "env-filter")]
847#[cfg_attr(docsrs, doc(cfg(feature = "env-filter")))]
848impl<N, E, W> SubscriberBuilder<N, E, crate::reload::Layer<crate::EnvFilter, Formatter<N, E, W>>, W>
849where
850 Formatter<N, E, W>: tracing_core::Subscriber + 'static,
851{
852 /// Returns a `Handle` that may be used to reload the constructed subscriber's
853 /// filter.
854 pub fn reload_handle(&self) -> crate::reload::Handle<crate::EnvFilter, Formatter<N, E, W>> {
855 self.filter.handle()
856 }
857}
858
859impl<N, E, F, W> SubscriberBuilder<N, E, F, W> {
860 /// Sets the field formatter that the subscriber being built will use to record
861 /// fields.
862 ///
863 /// For example:
864 /// ```rust
865 /// use tracing_subscriber::fmt::format;
866 /// use tracing_subscriber::prelude::*;
867 ///
868 /// let formatter =
869 /// // Construct a custom formatter for `Debug` fields
870 /// format::debug_fn(|writer, field, value| write!(writer, "{}: {:?}", field, value))
871 /// // Use the `tracing_subscriber::MakeFmtExt` trait to wrap the
872 /// // formatter so that a delimiter is added between fields.
873 /// .delimited(", ");
874 ///
875 /// let subscriber = tracing_subscriber::fmt()
876 /// .fmt_fields(formatter)
877 /// .finish();
878 /// # drop(subscriber)
879 /// ```
880 pub fn fmt_fields<N2>(self, fmt_fields: N2) -> SubscriberBuilder<N2, E, F, W>
881 where
882 N2: for<'writer> FormatFields<'writer> + 'static,
883 {
884 SubscriberBuilder {
885 filter: self.filter,
886 inner: self.inner.fmt_fields(fmt_fields),
887 }
888 }
889
890 /// Sets the [`EnvFilter`] that the subscriber will use to determine if
891 /// a span or event is enabled.
892 ///
893 /// Note that this method requires the "env-filter" feature flag to be enabled.
894 ///
895 /// If a filter was previously set, or a maximum level was set by the
896 /// [`with_max_level`] method, that value is replaced by the new filter.
897 ///
898 /// # Examples
899 ///
900 /// Setting a filter based on the value of the `RUST_LOG` environment
901 /// variable:
902 /// ```rust
903 /// use tracing_subscriber::{fmt, EnvFilter};
904 ///
905 /// fmt()
906 /// .with_env_filter(EnvFilter::from_default_env())
907 /// .init();
908 /// ```
909 ///
910 /// Setting a filter based on a pre-set filter directive string:
911 /// ```rust
912 /// use tracing_subscriber::fmt;
913 ///
914 /// fmt()
915 /// .with_env_filter("my_crate=info,my_crate::my_mod=debug,[my_span]=trace")
916 /// .init();
917 /// ```
918 ///
919 /// Adding additional directives to a filter constructed from an env var:
920 /// ```rust
921 /// use tracing_subscriber::{fmt, filter::{EnvFilter, LevelFilter}};
922 ///
923 /// # fn filter() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
924 /// let filter = EnvFilter::try_from_env("MY_CUSTOM_FILTER_ENV_VAR")?
925 /// // Set the base level when not matched by other directives to WARN.
926 /// .add_directive(LevelFilter::WARN.into())
927 /// // Set the max level for `my_crate::my_mod` to DEBUG, overriding
928 /// // any directives parsed from the env variable.
929 /// .add_directive("my_crate::my_mod=debug".parse()?);
930 ///
931 /// fmt()
932 /// .with_env_filter(filter)
933 /// .try_init()?;
934 /// # Ok(())}
935 /// ```
936 /// [`EnvFilter`]: super::filter::EnvFilter
937 /// [`with_max_level`]: SubscriberBuilder::with_max_level()
938 #[cfg(feature = "env-filter")]
939 #[cfg_attr(docsrs, doc(cfg(feature = "env-filter")))]
940 pub fn with_env_filter(
941 self,
942 filter: impl Into<crate::EnvFilter>,
943 ) -> SubscriberBuilder<N, E, crate::EnvFilter, W>
944 where
945 Formatter<N, E, W>: tracing_core::Subscriber + 'static,
946 {
947 let filter = filter.into();
948 SubscriberBuilder {
949 filter,
950 inner: self.inner,
951 }
952 }
953
954 /// Sets the maximum [verbosity level] that will be enabled by the
955 /// subscriber.
956 ///
957 /// If the max level has already been set, or a [`EnvFilter`] was added by
958 /// [`with_env_filter`], this replaces that configuration with the new
959 /// maximum level.
960 ///
961 /// # Examples
962 ///
963 /// Enable up to the `DEBUG` verbosity level:
964 /// ```rust
965 /// use tracing_subscriber::fmt;
966 /// use tracing::Level;
967 ///
968 /// fmt()
969 /// .with_max_level(Level::DEBUG)
970 /// .init();
971 /// ```
972 /// This subscriber won't record any spans or events!
973 /// ```rust
974 /// use tracing_subscriber::{fmt, filter::LevelFilter};
975 ///
976 /// let subscriber = fmt()
977 /// .with_max_level(LevelFilter::OFF)
978 /// .finish();
979 /// ```
980 /// [verbosity level]: tracing_core::Level
981 /// [`EnvFilter`]: struct@crate::filter::EnvFilter
982 /// [`with_env_filter`]: fn@Self::with_env_filter
983 pub fn with_max_level(
984 self,
985 filter: impl Into<LevelFilter>,
986 ) -> SubscriberBuilder<N, E, LevelFilter, W> {
987 let filter = filter.into();
988 SubscriberBuilder {
989 filter,
990 inner: self.inner,
991 }
992 }
993
994 /// Sets the [event formatter][`FormatEvent`] that the subscriber being built
995 /// will use to format events that occur.
996 ///
997 /// The event formatter may be any type implementing the [`FormatEvent`]
998 /// trait, which is implemented for all functions taking a [`FmtContext`], a
999 /// [`Writer`], and an [`Event`].
1000 ///
1001 /// # Examples
1002 ///
1003 /// Setting a type implementing [`FormatEvent`] as the formatter:
1004 ///
1005 /// ```rust
1006 /// use tracing_subscriber::fmt::format;
1007 ///
1008 /// let subscriber = tracing_subscriber::fmt()
1009 /// .event_format(format().compact())
1010 /// .finish();
1011 /// ```
1012 ///
1013 /// [`Writer`]: struct@self::format::Writer
1014 pub fn event_format<E2>(self, fmt_event: E2) -> SubscriberBuilder<N, E2, F, W>
1015 where
1016 E2: FormatEvent<Registry, N> + 'static,
1017 N: for<'writer> FormatFields<'writer> + 'static,
1018 W: for<'writer> MakeWriter<'writer> + 'static,
1019 {
1020 SubscriberBuilder {
1021 filter: self.filter,
1022 inner: self.inner.event_format(fmt_event),
1023 }
1024 }
1025
1026 /// Sets the [`MakeWriter`] that the subscriber being built will use to write events.
1027 ///
1028 /// # Examples
1029 ///
1030 /// Using `stderr` rather than `stdout`:
1031 ///
1032 /// ```rust
1033 /// use tracing_subscriber::fmt;
1034 /// use std::io;
1035 ///
1036 /// fmt()
1037 /// .with_writer(io::stderr)
1038 /// .init();
1039 /// ```
1040 pub fn with_writer<W2>(self, make_writer: W2) -> SubscriberBuilder<N, E, F, W2>
1041 where
1042 W2: for<'writer> MakeWriter<'writer> + 'static,
1043 {
1044 SubscriberBuilder {
1045 filter: self.filter,
1046 inner: self.inner.with_writer(make_writer),
1047 }
1048 }
1049
1050 /// Configures the subscriber to support [`libtest`'s output capturing][capturing] when used in
1051 /// unit tests.
1052 ///
1053 /// See [`TestWriter`] for additional details.
1054 ///
1055 /// # Examples
1056 ///
1057 /// Using [`TestWriter`] to let `cargo test` capture test output. Note that we do not install it
1058 /// globally as it may cause conflicts.
1059 ///
1060 /// ```rust
1061 /// use tracing_subscriber::fmt;
1062 /// use tracing::subscriber;
1063 ///
1064 /// subscriber::set_default(
1065 /// fmt()
1066 /// .with_test_writer()
1067 /// .finish()
1068 /// );
1069 /// ```
1070 ///
1071 /// [capturing]:
1072 /// https://doc.rust-lang.org/book/ch11-02-running-tests.html#showing-function-output
1073 /// [`TestWriter`]: writer::TestWriter
1074 pub fn with_test_writer(self) -> SubscriberBuilder<N, E, F, TestWriter> {
1075 SubscriberBuilder {
1076 filter: self.filter,
1077 inner: self.inner.with_writer(TestWriter::default()),
1078 }
1079 }
1080
1081 /// Updates the event formatter by applying a function to the existing event formatter.
1082 ///
1083 /// This sets the event formatter that the subscriber being built will use to record fields.
1084 ///
1085 /// # Examples
1086 ///
1087 /// Updating an event formatter:
1088 ///
1089 /// ```rust
1090 /// let subscriber = tracing_subscriber::fmt()
1091 /// .map_event_format(|e| e.compact())
1092 /// .finish();
1093 /// ```
1094 pub fn map_event_format<E2>(self, f: impl FnOnce(E) -> E2) -> SubscriberBuilder<N, E2, F, W>
1095 where
1096 E2: FormatEvent<Registry, N> + 'static,
1097 N: for<'writer> FormatFields<'writer> + 'static,
1098 W: for<'writer> MakeWriter<'writer> + 'static,
1099 {
1100 SubscriberBuilder {
1101 filter: self.filter,
1102 inner: self.inner.map_event_format(f),
1103 }
1104 }
1105
1106 /// Updates the field formatter by applying a function to the existing field formatter.
1107 ///
1108 /// This sets the field formatter that the subscriber being built will use to record fields.
1109 ///
1110 /// # Examples
1111 ///
1112 /// Updating a field formatter:
1113 ///
1114 /// ```rust
1115 /// use tracing_subscriber::field::MakeExt;
1116 /// let subscriber = tracing_subscriber::fmt()
1117 /// .map_fmt_fields(|f| f.debug_alt())
1118 /// .finish();
1119 /// ```
1120 pub fn map_fmt_fields<N2>(self, f: impl FnOnce(N) -> N2) -> SubscriberBuilder<N2, E, F, W>
1121 where
1122 N2: for<'writer> FormatFields<'writer> + 'static,
1123 {
1124 SubscriberBuilder {
1125 filter: self.filter,
1126 inner: self.inner.map_fmt_fields(f),
1127 }
1128 }
1129
1130 /// Updates the [`MakeWriter`] by applying a function to the existing [`MakeWriter`].
1131 ///
1132 /// This sets the [`MakeWriter`] that the subscriber being built will use to write events.
1133 ///
1134 /// # Examples
1135 ///
1136 /// Redirect output to stderr if level is <= WARN:
1137 ///
1138 /// ```rust
1139 /// use tracing::Level;
1140 /// use tracing_subscriber::fmt::{self, writer::MakeWriterExt};
1141 ///
1142 /// let stderr = std::io::stderr.with_max_level(Level::WARN);
1143 /// let layer = tracing_subscriber::fmt()
1144 /// .map_writer(move |w| stderr.or_else(w))
1145 /// .finish();
1146 /// ```
1147 pub fn map_writer<W2>(self, f: impl FnOnce(W) -> W2) -> SubscriberBuilder<N, E, F, W2>
1148 where
1149 W2: for<'writer> MakeWriter<'writer> + 'static,
1150 {
1151 SubscriberBuilder {
1152 filter: self.filter,
1153 inner: self.inner.map_writer(f),
1154 }
1155 }
1156}
1157
1158/// Install a global tracing subscriber that listens for events and
1159/// filters based on the value of the [`RUST_LOG` environment variable],
1160/// if one is not already set.
1161///
1162/// If the `tracing-log` feature is enabled, this will also install
1163/// the [`LogTracer`] to convert `log` records into `tracing` `Event`s.
1164///
1165/// This is shorthand for
1166///
1167/// ```rust
1168/// # fn doc() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
1169/// tracing_subscriber::fmt().try_init()
1170/// # }
1171/// ```
1172///
1173///
1174/// # Errors
1175///
1176/// Returns an Error if the initialization was unsuccessful,
1177/// likely because a global subscriber was already installed by another
1178/// call to `try_init`.
1179///
1180/// [`LogTracer`]:
1181/// https://docs.rs/tracing-log/0.1.0/tracing_log/struct.LogTracer.html
1182/// [`RUST_LOG` environment variable]: crate::filter::EnvFilter::DEFAULT_ENV
1183pub fn try_init() -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
1184 let builder = Subscriber::builder();
1185
1186 #[cfg(feature = "env-filter")]
1187 let builder = builder.with_env_filter(crate::EnvFilter::from_default_env());
1188
1189 // If `env-filter` is disabled, remove the default max level filter from the
1190 // subscriber; it will be added to the `Targets` filter instead if no filter
1191 // is set in `RUST_LOG`.
1192 // Replacing the default `LevelFilter` with an `EnvFilter` would imply this,
1193 // but we can't replace the builder's filter with a `Targets` filter yet.
1194 #[cfg(not(feature = "env-filter"))]
1195 let builder = builder.with_max_level(LevelFilter::TRACE);
1196
1197 let subscriber = builder.finish();
1198 #[cfg(not(feature = "env-filter"))]
1199 let subscriber = {
1200 use crate::{filter::Targets, layer::SubscriberExt};
1201 use std::{env, str::FromStr};
1202 let targets = match env::var("RUST_LOG") {
1203 Ok(var) => Targets::from_str(&var)
1204 .map_err(|e| {
1205 eprintln!("Ignoring `RUST_LOG={:?}`: {}", var, e);
1206 })
1207 .unwrap_or_default(),
1208 Err(env::VarError::NotPresent) => {
1209 Targets::new().with_default(Subscriber::DEFAULT_MAX_LEVEL)
1210 }
1211 Err(e) => {
1212 eprintln!("Ignoring `RUST_LOG`: {}", e);
1213 Targets::new().with_default(Subscriber::DEFAULT_MAX_LEVEL)
1214 }
1215 };
1216 subscriber.with(targets)
1217 };
1218
1219 subscriber.try_init().map_err(Into::into)
1220}
1221
1222/// Install a global tracing subscriber that listens for events and
1223/// filters based on the value of the [`RUST_LOG` environment variable].
1224///
1225/// The configuration of the subscriber initialized by this function
1226/// depends on what [feature flags](crate#feature-flags) are enabled.
1227///
1228/// If the `tracing-log` feature is enabled, this will also install
1229/// the LogTracer to convert `Log` records into `tracing` `Event`s.
1230///
1231/// If the `env-filter` feature is enabled, this is shorthand for
1232///
1233/// ```rust
1234/// # use tracing_subscriber::EnvFilter;
1235/// tracing_subscriber::fmt()
1236/// .with_env_filter(EnvFilter::from_default_env())
1237/// .init();
1238/// ```
1239///
1240/// # Panics
1241/// Panics if the initialization was unsuccessful, likely because a
1242/// global subscriber was already installed by another call to `try_init`.
1243///
1244/// [`RUST_LOG` environment variable]: crate::filter::EnvFilter::DEFAULT_ENV
1245pub fn init() {
1246 try_init().expect("Unable to install global subscriber")
1247}
1248
1249#[cfg(test)]
1250mod test {
1251 use crate::{
1252 filter::LevelFilter,
1253 fmt::{
1254 format::{self, Format},
1255 time,
1256 writer::MakeWriter,
1257 Subscriber,
1258 },
1259 };
1260 use std::{
1261 io,
1262 sync::{Arc, Mutex, MutexGuard, TryLockError},
1263 };
1264 use tracing_core::dispatcher::Dispatch;
1265
1266 pub(crate) struct MockWriter {
1267 buf: Arc<Mutex<Vec<u8>>>,
1268 }
1269
1270 impl MockWriter {
1271 pub(crate) fn new(buf: Arc<Mutex<Vec<u8>>>) -> Self {
1272 Self { buf }
1273 }
1274
1275 pub(crate) fn map_error<Guard>(err: TryLockError<Guard>) -> io::Error {
1276 match err {
1277 TryLockError::WouldBlock => io::Error::from(io::ErrorKind::WouldBlock),
1278 TryLockError::Poisoned(_) => io::Error::from(io::ErrorKind::Other),
1279 }
1280 }
1281
1282 pub(crate) fn buf(&self) -> io::Result<MutexGuard<'_, Vec<u8>>> {
1283 self.buf.try_lock().map_err(Self::map_error)
1284 }
1285 }
1286
1287 impl io::Write for MockWriter {
1288 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
1289 self.buf()?.write(buf)
1290 }
1291
1292 fn flush(&mut self) -> io::Result<()> {
1293 self.buf()?.flush()
1294 }
1295 }
1296
1297 #[derive(Clone, Default)]
1298 pub(crate) struct MockMakeWriter {
1299 buf: Arc<Mutex<Vec<u8>>>,
1300 }
1301
1302 impl MockMakeWriter {
1303 pub(crate) fn new(buf: Arc<Mutex<Vec<u8>>>) -> Self {
1304 Self { buf }
1305 }
1306
1307 // this is currently only used by the JSON formatter tests. if we need
1308 // it elsewhere in the future, feel free to remove the `#[cfg]`
1309 // attribute!
1310 #[cfg(feature = "json")]
1311 pub(crate) fn buf(&self) -> MutexGuard<'_, Vec<u8>> {
1312 self.buf.lock().unwrap()
1313 }
1314
1315 pub(crate) fn get_string(&self) -> String {
1316 let mut buf = self.buf.lock().expect("lock shouldn't be poisoned");
1317 let string = std::str::from_utf8(&buf[..])
1318 .expect("formatter should not have produced invalid utf-8")
1319 .to_owned();
1320 buf.clear();
1321 string
1322 }
1323 }
1324
1325 impl<'a> MakeWriter<'a> for MockMakeWriter {
1326 type Writer = MockWriter;
1327
1328 fn make_writer(&'a self) -> Self::Writer {
1329 MockWriter::new(self.buf.clone())
1330 }
1331 }
1332
1333 #[test]
1334 fn impls() {
1335 let f = Format::default().with_timer(time::Uptime::default());
1336 let subscriber = Subscriber::builder().event_format(f).finish();
1337 let _dispatch = Dispatch::new(subscriber);
1338
1339 let f = format::Format::default();
1340 let subscriber = Subscriber::builder().event_format(f).finish();
1341 let _dispatch = Dispatch::new(subscriber);
1342
1343 let f = format::Format::default().compact();
1344 let subscriber = Subscriber::builder().event_format(f).finish();
1345 let _dispatch = Dispatch::new(subscriber);
1346 }
1347
1348 #[test]
1349 fn subscriber_downcasts() {
1350 let subscriber = Subscriber::builder().finish();
1351 let dispatch = Dispatch::new(subscriber);
1352 assert!(dispatch.downcast_ref::<Subscriber>().is_some());
1353 }
1354
1355 #[test]
1356 fn subscriber_downcasts_to_parts() {
1357 let subscriber = Subscriber::new();
1358 let dispatch = Dispatch::new(subscriber);
1359 assert!(dispatch.downcast_ref::<format::DefaultFields>().is_some());
1360 assert!(dispatch.downcast_ref::<LevelFilter>().is_some());
1361 assert!(dispatch.downcast_ref::<format::Format>().is_some())
1362 }
1363
1364 #[test]
1365 fn is_lookup_span() {
1366 fn assert_lookup_span<T: for<'a> crate::registry::LookupSpan<'a>>(_: T) {}
1367 let subscriber = Subscriber::new();
1368 assert_lookup_span(subscriber)
1369 }
1370}
1371