1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
//! A [filter] that enables or disables spans and events based on their [target] and [level].
//!
//! See [`Targets`] for details.
//!
//! [target]: tracing_core::Metadata::target
//! [level]: tracing_core::Level
//! [filter]: crate::layer#filtering-with-layers

use crate::{
    filter::{
        directive::{DirectiveSet, ParseError, StaticDirective},
        LevelFilter,
    },
    layer,
};
use std::{
    iter::{Extend, FilterMap, FromIterator},
    str::FromStr,
};
use tracing_core::{Interest, Metadata, Subscriber};

/// A filter that enables or disables spans and events based on their [target]
/// and [level].
///
/// Targets are typically equal to the Rust module path of the code where the
/// span or event was recorded, although they may be overridden.
///
/// This type can be used for both [per-layer filtering][plf] (using its
/// [`Filter`] implementation) and [global filtering][global] (using its
/// [`Layer`] implementation).
///
/// See the [documentation on filtering with layers][filtering] for details.
///
/// # Filtering With `Targets`
///
/// A `Targets` filter consists of one or more [target] prefixes, paired with
/// [`LevelFilter`]s. If a span or event's [target] begins with one of those
/// prefixes, and its [level] is at or below the [`LevelFilter`] enabled for
/// that prefix, then the span or event will be enabled.
///
/// This is similar to the behavior implemented by the [`env_logger` crate] in
/// the `log` ecosystem.
///
/// The [`EnvFilter`] type also provided by this crate is very similar to `Targets`,
/// but is capable of a more sophisticated form of filtering where events may
/// also be enabled or disabled based on the span they are recorded in.
/// `Targets` can be thought of as a lighter-weight form of [`EnvFilter`] that
/// can be used instead when this dynamic filtering is not required.
///
/// # Examples
///
/// A `Targets` filter can be constructed by programmatically adding targets and
/// levels to enable:
///
/// ```
/// use tracing_subscriber::{filter, prelude::*};
/// use tracing_core::Level;
///
/// let filter = filter::Targets::new()
///     // Enable the `INFO` level for anything in `my_crate`
///     .with_target("my_crate", Level::INFO)
///     // Enable the `DEBUG` level for a specific module.
///     .with_target("my_crate::interesting_module", Level::DEBUG);
///
/// // Build a new subscriber with the `fmt` layer using the `Targets`
/// // filter we constructed above.
/// tracing_subscriber::registry()
///     .with(tracing_subscriber::fmt::layer())
///     .with(filter)
///     .init();
/// ```
///
/// [`LevelFilter::OFF`] can be used to disable a particular target:
/// ```
/// use tracing_subscriber::filter::{Targets, LevelFilter};
/// use tracing_core::Level;
///
/// let filter = Targets::new()
///     .with_target("my_crate", Level::INFO)
///     // Disable all traces from `annoying_module`.
///     .with_target("my_crate::annoying_module", LevelFilter::OFF);
/// # drop(filter);
/// ```
///
/// Alternatively, `Targets` implements [`std::str::FromStr`], allowing it to be
/// parsed from a comma-delimited list of `target=level` pairs. For example:
///
/// ```rust
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// use tracing_subscriber::filter;
/// use tracing_core::Level;
///
/// let filter = "my_crate=info,my_crate::interesting_module=trace,other_crate=debug"
///     .parse::<filter::Targets>()?;
///
/// // The parsed filter is identical to a filter constructed using `with_target`:
/// assert_eq!(
///     filter,
///     filter::Targets::new()
///         .with_target("my_crate", Level::INFO)
///         .with_target("my_crate::interesting_module", Level::TRACE)
///         .with_target("other_crate", Level::DEBUG)
/// );
/// # Ok(()) }
/// ```
///
/// This is particularly useful when the list of enabled targets is configurable
/// by the user at runtime.
///
/// The `Targets` filter can be used as a [per-layer filter][plf] *and* as a
/// [global filter]:
///
/// ```rust
/// use tracing_subscriber::{
///     fmt,
///     filter::{Targets, LevelFilter},
///     prelude::*,
/// };
/// use tracing_core::Level;
/// use std::{sync::Arc, fs::File};
/// # fn docs() -> Result<(), Box<dyn std::error::Error>> {
///
/// // A layer that logs events to stdout using the human-readable "pretty"
/// // format.
/// let stdout_log = fmt::layer().pretty();
///
/// // A layer that logs events to a file, using the JSON format.
/// let file = File::create("debug_log.json")?;
/// let debug_log = fmt::layer()
///     .with_writer(Arc::new(file))
///     .json();
///
/// tracing_subscriber::registry()
///     // Only log INFO and above to stdout, unless the span or event
///     // has the `my_crate::cool_module` target prefix.
///     .with(stdout_log
///         .with_filter(
///             Targets::default()
///                 .with_target("my_crate::cool_module", Level::DEBUG)
///                 .with_default(Level::INFO)
///        )
///     )
///     // Log everything enabled by the global filter to `debug_log.json`.
///     .with(debug_log)
///     // Configure a global filter for the whole subscriber stack. This will
///     // control what spans and events are recorded by both the `debug_log`
///     // and the `stdout_log` layers, and `stdout_log` will *additionally* be
///     // filtered by its per-layer filter.
///     .with(
///         Targets::default()
///             .with_target("my_crate", Level::TRACE)
///             .with_target("other_crate", Level::INFO)
///             .with_target("other_crate::annoying_module", LevelFilter::OFF)
///             .with_target("third_crate", Level::DEBUG)
///     ).init();
/// # Ok(()) }
///```
///
/// [target]: tracing_core::Metadata::target
/// [level]: tracing_core::Level
/// [`Filter`]: crate::layer::Filter
/// [`Layer`]: crate::layer::Layer
/// [plf]: crate::layer#per-layer-filtering
/// [global]: crate::layer#global-filtering
/// [filtering]: crate::layer#filtering-with-layers
/// [`env_logger` crate]: https://docs.rs/env_logger/0.9.0/env_logger/index.html#enabling-logging
/// [`EnvFilter`]: crate::filter::EnvFilter
#[derive(Debug, Default, Clone, PartialEq)]
pub struct Targets(DirectiveSet<StaticDirective>);

impl Targets {
    /// Returns a new `Targets` filter.
    ///
    /// This filter will enable no targets. Call [`with_target`] or [`with_targets`]
    /// to add enabled targets, and [`with_default`] to change the default level
    /// enabled for spans and events that didn't match any of the provided targets.
    ///
    /// [`with_target`]: Targets::with_target
    /// [`with_targets`]: Targets::with_targets
    /// [`with_default`]: Targets::with_default
    pub fn new() -> Self {
        Self::default()
    }

    /// Enables spans and events with [target]s starting with the provided target
    /// prefix if they are at or below the provided [`LevelFilter`].
    ///
    /// # Examples
    ///
    /// ```
    /// use tracing_subscriber::filter;
    /// use tracing_core::Level;
    ///
    /// let filter = filter::Targets::new()
    ///     // Enable the `INFO` level for anything in `my_crate`
    ///     .with_target("my_crate", Level::INFO)
    ///     // Enable the `DEBUG` level for a specific module.
    ///     .with_target("my_crate::interesting_module", Level::DEBUG);
    /// # drop(filter);
    /// ```
    ///
    /// [`LevelFilter::OFF`] can be used to disable a particular target:
    /// ```
    /// use tracing_subscriber::filter::{Targets, LevelFilter};
    /// use tracing_core::Level;
    ///
    /// let filter = Targets::new()
    ///     .with_target("my_crate", Level::INFO)
    ///     // Disable all traces from `annoying_module`.
    ///     .with_target("my_crate::interesting_module", LevelFilter::OFF);
    /// # drop(filter);
    /// ```
    ///
    /// [target]: tracing_core::Metadata::target
    pub fn with_target(mut self, target: impl Into<String>, level: impl Into<LevelFilter>) -> Self {
        self.0.add(StaticDirective::new(
            Some(target.into()),
            Default::default(),
            level.into(),
        ));
        self
    }
    /// Adds [target]s from an iterator of [target]-[`LevelFilter`] pairs to this filter.
    ///
    /// # Examples
    ///
    /// ```
    /// use tracing_subscriber::filter;
    /// use tracing_core::Level;
    ///
    /// let filter = filter::Targets::new()
    ///     .with_targets(vec![
    ///         ("my_crate", Level::INFO),
    ///         ("my_crate::some_module", Level::DEBUG),
    ///         ("my_crate::other_module::cool_stuff", Level::TRACE),
    ///         ("other_crate", Level::WARN)
    ///     ]);
    /// # drop(filter);
    /// ```
    ///
    /// [`LevelFilter::OFF`] can be used to disable a particular target:
    /// ```
    /// use tracing_subscriber::filter::{Targets, LevelFilter};
    /// use tracing_core::Level;
    ///
    /// let filter = Targets::new()
    ///     .with_target("my_crate", Level::INFO)
    ///     // Disable all traces from `annoying_module`.
    ///     .with_target("my_crate::interesting_module", LevelFilter::OFF);
    /// # drop(filter);
    /// ```
    ///
    /// [target]: tracing_core::Metadata::target
    pub fn with_targets<T, L>(mut self, targets: impl IntoIterator<Item = (T, L)>) -> Self
    where
        String: From<T>,
        LevelFilter: From<L>,
    {
        self.extend(targets);
        self
    }

    /// Sets the default level to enable for spans and events whose targets did
    /// not match any of the configured prefixes.
    ///
    /// By default, this is [`LevelFilter::OFF`]. This means that spans and
    /// events will only be enabled if they match one of the configured target
    /// prefixes. If this is changed to a different [`LevelFilter`], spans and
    /// events with targets that did not match any of the configured prefixes
    /// will be enabled if their level is at or below the provided level.
    pub fn with_default(mut self, level: impl Into<LevelFilter>) -> Self {
        self.0
            .add(StaticDirective::new(None, Default::default(), level.into()));
        self
    }

    /// Returns an iterator over the [target]-[`LevelFilter`] pairs in this filter.
    ///
    /// The order of iteration is undefined.
    ///
    /// # Examples
    ///
    /// ```
    /// use tracing_subscriber::filter::{Targets, LevelFilter};
    /// use tracing_core::Level;
    ///
    /// let filter = Targets::new()
    ///     .with_target("my_crate", Level::INFO)
    ///     .with_target("my_crate::interesting_module", Level::DEBUG);
    ///
    /// let mut targets: Vec<_> = filter.iter().collect();
    /// targets.sort();
    ///
    /// assert_eq!(targets, vec![
    ///     ("my_crate", LevelFilter::INFO),
    ///     ("my_crate::interesting_module", LevelFilter::DEBUG),
    /// ]);
    /// ```
    ///
    /// [target]: tracing_core::Metadata::target
    pub fn iter(&self) -> Iter<'_> {
        self.into_iter()
    }

    #[inline]
    fn interested(&self, metadata: &'static Metadata<'static>) -> Interest {
        if self.0.enabled(metadata) {
            Interest::always()
        } else {
            Interest::never()
        }
    }
}

impl<T, L> Extend<(T, L)> for Targets
where
    T: Into<String>,
    L: Into<LevelFilter>,
{
    fn extend<I: IntoIterator<Item = (T, L)>>(&mut self, iter: I) {
        let iter = iter.into_iter().map(|(target, level)| {
            StaticDirective::new(Some(target.into()), Default::default(), level.into())
        });
        self.0.extend(iter);
    }
}

impl<T, L> FromIterator<(T, L)> for Targets
where
    T: Into<String>,
    L: Into<LevelFilter>,
{
    fn from_iter<I: IntoIterator<Item = (T, L)>>(iter: I) -> Self {
        let mut this = Self::default();
        this.extend(iter);
        this
    }
}

impl FromStr for Targets {
    type Err = ParseError;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        s.split(',')
            .map(StaticDirective::from_str)
            .collect::<Result<_, _>>()
            .map(Self)
    }
}

impl<S> layer::Layer<S> for Targets
where
    S: Subscriber,
{
    fn enabled(&self, metadata: &Metadata<'_>, _: layer::Context<'_, S>) -> bool {
        self.0.enabled(metadata)
    }

    fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest {
        self.interested(metadata)
    }

    fn max_level_hint(&self) -> Option<LevelFilter> {
        Some(self.0.max_level)
    }
}

#[cfg(feature = "registry")]
#[cfg_attr(docsrs, doc(cfg(feature = "registry")))]
impl<S> layer::Filter<S> for Targets {
    fn enabled(&self, metadata: &Metadata<'_>, _: &layer::Context<'_, S>) -> bool {
        self.0.enabled(metadata)
    }

    fn callsite_enabled(&self, metadata: &'static Metadata<'static>) -> Interest {
        self.interested(metadata)
    }

    fn max_level_hint(&self) -> Option<LevelFilter> {
        Some(self.0.max_level)
    }
}

impl IntoIterator for Targets {
    type Item = (String, LevelFilter);

    type IntoIter = IntoIter;

    fn into_iter(self) -> Self::IntoIter {
        IntoIter::new(self)
    }
}

impl<'a> IntoIterator for &'a Targets {
    type Item = (&'a str, LevelFilter);

    type IntoIter = Iter<'a>;

    fn into_iter(self) -> Self::IntoIter {
        Iter::new(self)
    }
}

/// An owning iterator over the [target]-[level] pairs of a `Targets` filter.
///
/// This struct is created by the `IntoIterator` trait implementation of [`Targets`].
///
/// # Examples
///
/// Merge the targets from one `Targets` with another:
///
/// ```
/// use tracing_subscriber::filter::Targets;
/// use tracing_core::Level;
///
/// let mut filter = Targets::new().with_target("my_crate", Level::INFO);
/// let overrides = Targets::new().with_target("my_crate::interesting_module", Level::DEBUG);
///
/// filter.extend(overrides);
/// # drop(filter);
/// ```
///
/// [target]: tracing_core::Metadata::target
/// [level]: tracing_core::Level
#[derive(Debug)]
pub struct IntoIter(
    #[allow(clippy::type_complexity)] // alias indirection would probably make this more confusing
    FilterMap<
        <DirectiveSet<StaticDirective> as IntoIterator>::IntoIter,
        fn(StaticDirective) -> Option<(String, LevelFilter)>,
    >,
);

impl IntoIter {
    fn new(targets: Targets) -> Self {
        Self(targets.0.into_iter().filter_map(|directive| {
            let level = directive.level;
            directive.target.map(|target| (target, level))
        }))
    }
}

impl Iterator for IntoIter {
    type Item = (String, LevelFilter);

    fn next(&mut self) -> Option<Self::Item> {
        self.0.next()
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.0.size_hint()
    }
}

/// A borrowing iterator over the [target]-[level] pairs of a `Targets` filter.
///
/// This struct is created by [`iter`] method of [`Targets`], or from the `IntoIterator`
/// implementation for `&Targets`.
///
/// [target]: tracing_core::Metadata::target
/// [level]: tracing_core::Level
/// [`iter`]: Targets::iter
#[derive(Debug)]
pub struct Iter<'a>(
    FilterMap<
        std::slice::Iter<'a, StaticDirective>,
        fn(&'a StaticDirective) -> Option<(&'a str, LevelFilter)>,
    >,
);

impl<'a> Iter<'a> {
    fn new(targets: &'a Targets) -> Self {
        Self(targets.0.iter().filter_map(|directive| {
            directive
                .target
                .as_deref()
                .map(|target| (target, directive.level))
        }))
    }
}

impl<'a> Iterator for Iter<'a> {
    type Item = (&'a str, LevelFilter);

    fn next(&mut self) -> Option<Self::Item> {
        self.0.next()
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        self.0.size_hint()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn expect_parse(s: &str) -> Targets {
        match dbg!(s).parse::<Targets>() {
            Err(e) => panic!("string {:?} did not parse successfully: {}", s, e),
            Ok(e) => e,
        }
    }

    fn expect_parse_ralith(s: &str) {
        let dirs = expect_parse(s).0.into_vec();
        assert_eq!(dirs.len(), 2, "\nparsed: {:#?}", dirs);
        assert_eq!(dirs[0].target, Some("server".to_string()));
        assert_eq!(dirs[0].level, LevelFilter::DEBUG);
        assert_eq!(dirs[0].field_names, Vec::<String>::new());

        assert_eq!(dirs[1].target, Some("common".to_string()));
        assert_eq!(dirs[1].level, LevelFilter::INFO);
        assert_eq!(dirs[1].field_names, Vec::<String>::new());
    }

    fn expect_parse_level_directives(s: &str) {
        let dirs = expect_parse(s).0.into_vec();
        assert_eq!(dirs.len(), 6, "\nparsed: {:#?}", dirs);

        assert_eq!(dirs[0].target, Some("crate3::mod2::mod1".to_string()));
        assert_eq!(dirs[0].level, LevelFilter::OFF);
        assert_eq!(dirs[0].field_names, Vec::<String>::new());

        assert_eq!(dirs[1].target, Some("crate1::mod2::mod3".to_string()));
        assert_eq!(dirs[1].level, LevelFilter::INFO);
        assert_eq!(dirs[1].field_names, Vec::<String>::new());

        assert_eq!(dirs[2].target, Some("crate1::mod2".to_string()));
        assert_eq!(dirs[2].level, LevelFilter::WARN);
        assert_eq!(dirs[2].field_names, Vec::<String>::new());

        assert_eq!(dirs[3].target, Some("crate1::mod1".to_string()));
        assert_eq!(dirs[3].level, LevelFilter::ERROR);
        assert_eq!(dirs[3].field_names, Vec::<String>::new());

        assert_eq!(dirs[4].target, Some("crate3".to_string()));
        assert_eq!(dirs[4].level, LevelFilter::TRACE);
        assert_eq!(dirs[4].field_names, Vec::<String>::new());

        assert_eq!(dirs[5].target, Some("crate2".to_string()));
        assert_eq!(dirs[5].level, LevelFilter::DEBUG);
        assert_eq!(dirs[5].field_names, Vec::<String>::new());
    }

    #[test]
    fn parse_ralith() {
        expect_parse_ralith("common=info,server=debug");
    }

    #[test]
    fn parse_ralith_uc() {
        expect_parse_ralith("common=INFO,server=DEBUG");
    }

    #[test]
    fn parse_ralith_mixed() {
        expect_parse("common=iNfo,server=dEbUg");
    }

    #[test]
    fn expect_parse_valid() {
        let dirs = expect_parse("crate1::mod1=error,crate1::mod2,crate2=debug,crate3=off")
            .0
            .into_vec();
        assert_eq!(dirs.len(), 4, "\nparsed: {:#?}", dirs);
        assert_eq!(dirs[0].target, Some("crate1::mod2".to_string()));
        assert_eq!(dirs[0].level, LevelFilter::TRACE);
        assert_eq!(dirs[0].field_names, Vec::<String>::new());

        assert_eq!(dirs[1].target, Some("crate1::mod1".to_string()));
        assert_eq!(dirs[1].level, LevelFilter::ERROR);
        assert_eq!(dirs[1].field_names, Vec::<String>::new());

        assert_eq!(dirs[2].target, Some("crate3".to_string()));
        assert_eq!(dirs[2].level, LevelFilter::OFF);
        assert_eq!(dirs[2].field_names, Vec::<String>::new());

        assert_eq!(dirs[3].target, Some("crate2".to_string()));
        assert_eq!(dirs[3].level, LevelFilter::DEBUG);
        assert_eq!(dirs[3].field_names, Vec::<String>::new());
    }

    #[test]
    fn parse_level_directives() {
        expect_parse_level_directives(
            "crate1::mod1=error,crate1::mod2=warn,crate1::mod2::mod3=info,\
             crate2=debug,crate3=trace,crate3::mod2::mod1=off",
        )
    }

    #[test]
    fn parse_uppercase_level_directives() {
        expect_parse_level_directives(
            "crate1::mod1=ERROR,crate1::mod2=WARN,crate1::mod2::mod3=INFO,\
             crate2=DEBUG,crate3=TRACE,crate3::mod2::mod1=OFF",
        )
    }

    #[test]
    fn parse_numeric_level_directives() {
        expect_parse_level_directives(
            "crate1::mod1=1,crate1::mod2=2,crate1::mod2::mod3=3,crate2=4,\
             crate3=5,crate3::mod2::mod1=0",
        )
    }

    #[test]
    fn targets_iter() {
        let filter = expect_parse("crate1::mod1=error,crate1::mod2,crate2=debug,crate3=off")
            .with_default(LevelFilter::WARN);

        let mut targets: Vec<_> = filter.iter().collect();
        targets.sort();

        assert_eq!(
            targets,
            vec![
                ("crate1::mod1", LevelFilter::ERROR),
                ("crate1::mod2", LevelFilter::TRACE),
                ("crate2", LevelFilter::DEBUG),
                ("crate3", LevelFilter::OFF),
            ]
        );
    }

    #[test]
    fn targets_into_iter() {
        let filter = expect_parse("crate1::mod1=error,crate1::mod2,crate2=debug,crate3=off")
            .with_default(LevelFilter::WARN);

        let mut targets: Vec<_> = filter.into_iter().collect();
        targets.sort();

        assert_eq!(
            targets,
            vec![
                ("crate1::mod1".to_string(), LevelFilter::ERROR),
                ("crate1::mod2".to_string(), LevelFilter::TRACE),
                ("crate2".to_string(), LevelFilter::DEBUG),
                ("crate3".to_string(), LevelFilter::OFF),
            ]
        );
    }

    #[test]
    fn size_of_filters() {
        fn print_sz(s: &str) {
            let filter = s.parse::<Targets>().expect("filter should parse");
            println!(
                "size_of_val({:?})\n -> {}B",
                s,
                std::mem::size_of_val(&filter)
            );
        }

        print_sz("info");

        print_sz("foo=debug");

        print_sz(
            "crate1::mod1=error,crate1::mod2=warn,crate1::mod2::mod3=info,\
            crate2=debug,crate3=trace,crate3::mod2::mod1=off",
        );
    }
}