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
// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

//! Substrate logging library.
//!
//! This crate uses tokio's [tracing](https://github.com/tokio-rs/tracing/) library for logging.

#![warn(missing_docs)]

mod directives;
mod event_format;
mod fast_local_time;
mod layers;
mod stderr_writer;

pub(crate) type DefaultLogger = stderr_writer::MakeStderrWriter;

pub use directives::*;
pub use sc_tracing_proc_macro::*;

use is_terminal::IsTerminal;
use std::io;
use tracing::Subscriber;
use tracing_subscriber::{
	filter::LevelFilter,
	fmt::{
		format, FormatEvent, FormatFields, Formatter, Layer as FmtLayer, MakeWriter,
		SubscriberBuilder,
	},
	layer::{self, SubscriberExt},
	registry::LookupSpan,
	EnvFilter, FmtSubscriber, Layer, Registry,
};

pub use event_format::*;
pub use fast_local_time::FastLocalTime;
pub use layers::*;

use stderr_writer::MakeStderrWriter;

/// Logging Result typedef.
pub type Result<T> = std::result::Result<T, Error>;

/// Logging errors.
#[derive(Debug, thiserror::Error)]
#[allow(missing_docs)]
#[non_exhaustive]
#[error(transparent)]
pub enum Error {
	IoError(#[from] io::Error),
	SetGlobalDefaultError(#[from] tracing::subscriber::SetGlobalDefaultError),
	DirectiveParseError(#[from] tracing_subscriber::filter::ParseError),
	SetLoggerError(#[from] tracing_log::log_tracer::SetLoggerError),
}

macro_rules! enable_log_reloading {
	($builder:expr) => {{
		let builder = $builder.with_filter_reloading();
		let handle = builder.reload_handle();
		set_reload_handle(handle);
		builder
	}};
}

/// Convert a `Option<LevelFilter>` to a [`log::LevelFilter`].
///
/// `None` is interpreted as `Info`.
fn to_log_level_filter(level_filter: Option<LevelFilter>) -> log::LevelFilter {
	match level_filter {
		Some(LevelFilter::INFO) | None => log::LevelFilter::Info,
		Some(LevelFilter::TRACE) => log::LevelFilter::Trace,
		Some(LevelFilter::WARN) => log::LevelFilter::Warn,
		Some(LevelFilter::ERROR) => log::LevelFilter::Error,
		Some(LevelFilter::DEBUG) => log::LevelFilter::Debug,
		Some(LevelFilter::OFF) => log::LevelFilter::Off,
	}
}

/// Common implementation to get the subscriber.
fn prepare_subscriber<N, E, F, W>(
	directives: &str,
	profiling_targets: Option<&str>,
	force_colors: Option<bool>,
	detailed_output: bool,
	builder_hook: impl Fn(
		SubscriberBuilder<format::DefaultFields, EventFormat, EnvFilter, DefaultLogger>,
	) -> SubscriberBuilder<N, E, F, W>,
) -> Result<impl Subscriber + for<'a> LookupSpan<'a>>
where
	N: for<'writer> FormatFields<'writer> + 'static,
	E: FormatEvent<Registry, N> + 'static,
	W: for<'writer> MakeWriter<'writer> + 'static,
	F: layer::Layer<Formatter<N, E, W>> + Send + Sync + 'static,
	FmtLayer<Registry, N, E, W>: layer::Layer<Registry> + Send + Sync + 'static,
{
	// Accept all valid directives and print invalid ones
	fn parse_user_directives(mut env_filter: EnvFilter, dirs: &str) -> Result<EnvFilter> {
		for dir in dirs.split(',') {
			env_filter = env_filter.add_directive(parse_default_directive(dir)?);
		}
		Ok(env_filter)
	}

	// Initialize filter - ensure to use `parse_default_directive` for any defaults to persist
	// after log filter reloading by RPC
	let mut env_filter = EnvFilter::default()
		// Enable info
		.add_directive(parse_default_directive("info").expect("provided directive is valid"))
		// Disable info logging by default for some modules.
		.add_directive(parse_default_directive("ws=off").expect("provided directive is valid"))
		.add_directive(parse_default_directive("yamux=off").expect("provided directive is valid"))
		.add_directive(
			parse_default_directive("regalloc=off").expect("provided directive is valid"),
		)
		.add_directive(
			parse_default_directive("cranelift_codegen=off").expect("provided directive is valid"),
		)
		// Set warn logging by default for some modules.
		.add_directive(
			parse_default_directive("cranelift_wasm=warn").expect("provided directive is valid"),
		)
		.add_directive(parse_default_directive("hyper=warn").expect("provided directive is valid"))
		.add_directive(
			parse_default_directive("trust_dns_proto=off").expect("provided directive is valid"),
		)
		.add_directive(
			parse_default_directive("hickory_proto=off").expect("provided directive is valid"),
		)
		.add_directive(
			parse_default_directive("libp2p_mdns::behaviour::iface=off")
				.expect("provided directive is valid"),
		)
		// Disable annoying log messages from rustls
		.add_directive(
			parse_default_directive("rustls::common_state=off")
				.expect("provided directive is valid"),
		)
		.add_directive(
			parse_default_directive("rustls::conn=off").expect("provided directive is valid"),
		);

	if let Ok(lvl) = std::env::var("RUST_LOG") {
		if lvl != "" {
			env_filter = parse_user_directives(env_filter, &lvl)?;
		}
	}

	if directives != "" {
		env_filter = parse_user_directives(env_filter, directives)?;
	}

	if let Some(profiling_targets) = profiling_targets {
		env_filter = parse_user_directives(env_filter, profiling_targets)?;
		env_filter = env_filter.add_directive(
			parse_default_directive("sc_tracing=trace").expect("provided directive is valid"),
		);
	}

	let max_level_hint = Layer::<FmtSubscriber>::max_level_hint(&env_filter);
	let max_level = to_log_level_filter(max_level_hint);

	tracing_log::LogTracer::builder().with_max_level(max_level).init()?;

	// If we're only logging `INFO` entries then we'll use a simplified logging format.
	let detailed_output = match max_level_hint {
		Some(level) if level <= tracing_subscriber::filter::LevelFilter::INFO => false,
		_ => true,
	} || detailed_output;

	let enable_color = force_colors.unwrap_or_else(|| io::stderr().is_terminal());
	let timer = fast_local_time::FastLocalTime { with_fractional: detailed_output };

	// We need to set both together, because we are may printing to `stdout` and `stderr`.
	console::set_colors_enabled(enable_color);
	console::set_colors_enabled_stderr(enable_color);

	let event_format = EventFormat {
		timer,
		display_target: detailed_output,
		display_level: detailed_output,
		display_thread_name: detailed_output,
		dup_to_stdout: !io::stderr().is_terminal() && io::stdout().is_terminal(),
	};
	let builder = FmtSubscriber::builder().with_env_filter(env_filter);

	let builder = builder.with_span_events(format::FmtSpan::NONE);

	let builder = builder.with_writer(MakeStderrWriter::default());

	let builder = builder.event_format(event_format);

	let builder = builder_hook(builder);

	let subscriber = builder.finish().with(PrefixLayer);

	Ok(subscriber)
}

/// A builder that is used to initialize the global logger.
pub struct LoggerBuilder {
	directives: String,
	profiling: Option<(crate::TracingReceiver, String)>,
	custom_profiler: Option<Box<dyn crate::TraceHandler>>,
	log_reloading: bool,
	force_colors: Option<bool>,
	detailed_output: bool,
}

impl LoggerBuilder {
	/// Create a new [`LoggerBuilder`] which can be used to initialize the global logger.
	pub fn new<S: Into<String>>(directives: S) -> Self {
		Self {
			directives: directives.into(),
			profiling: None,
			custom_profiler: None,
			log_reloading: false,
			force_colors: None,
			detailed_output: false,
		}
	}

	/// Set up the profiling.
	pub fn with_profiling<S: Into<String>>(
		&mut self,
		tracing_receiver: crate::TracingReceiver,
		profiling_targets: S,
	) -> &mut Self {
		self.profiling = Some((tracing_receiver, profiling_targets.into()));
		self
	}

	/// Add a custom profiler.
	pub fn with_custom_profiling(
		&mut self,
		custom_profiler: Box<dyn crate::TraceHandler>,
	) -> &mut Self {
		self.custom_profiler = Some(custom_profiler);
		self
	}

	/// Wether or not to disable log reloading.
	pub fn with_log_reloading(&mut self, enabled: bool) -> &mut Self {
		self.log_reloading = enabled;
		self
	}

	/// Whether detailed log output should be enabled.
	///
	/// This includes showing the log target, log level and thread name.
	///
	/// This will be automatically enabled when there is a log level enabled that is higher than
	/// `info`.
	pub fn with_detailed_output(&mut self, detailed: bool) -> &mut Self {
		self.detailed_output = detailed;
		self
	}

	/// Force enable/disable colors.
	pub fn with_colors(&mut self, enable: bool) -> &mut Self {
		self.force_colors = Some(enable);
		self
	}

	/// Initialize the global logger
	///
	/// This sets various global logging and tracing instances and thus may only be called once.
	pub fn init(self) -> Result<()> {
		if let Some((tracing_receiver, profiling_targets)) = self.profiling {
			if self.log_reloading {
				let subscriber = prepare_subscriber(
					&self.directives,
					Some(&profiling_targets),
					self.force_colors,
					self.detailed_output,
					|builder| enable_log_reloading!(builder),
				)?;
				let mut profiling =
					crate::ProfilingLayer::new(tracing_receiver, &profiling_targets);

				self.custom_profiler
					.into_iter()
					.for_each(|profiler| profiling.add_handler(profiler));

				tracing::subscriber::set_global_default(subscriber.with(profiling))?;

				Ok(())
			} else {
				let subscriber = prepare_subscriber(
					&self.directives,
					Some(&profiling_targets),
					self.force_colors,
					self.detailed_output,
					|builder| builder,
				)?;
				let mut profiling =
					crate::ProfilingLayer::new(tracing_receiver, &profiling_targets);

				self.custom_profiler
					.into_iter()
					.for_each(|profiler| profiling.add_handler(profiler));

				tracing::subscriber::set_global_default(subscriber.with(profiling))?;

				Ok(())
			}
		} else if self.log_reloading {
			let subscriber = prepare_subscriber(
				&self.directives,
				None,
				self.force_colors,
				self.detailed_output,
				|builder| enable_log_reloading!(builder),
			)?;

			tracing::subscriber::set_global_default(subscriber)?;

			Ok(())
		} else {
			let subscriber = prepare_subscriber(
				&self.directives,
				None,
				self.force_colors,
				self.detailed_output,
				|builder| builder,
			)?;

			tracing::subscriber::set_global_default(subscriber)?;

			Ok(())
		}
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use crate as sc_tracing;
	use log::info;
	use std::{
		collections::BTreeMap,
		env,
		process::Command,
		sync::{
			atomic::{AtomicBool, AtomicUsize, Ordering},
			Arc,
		},
	};
	use tracing::{metadata::Kind, subscriber::Interest, Callsite, Level, Metadata};

	const EXPECTED_LOG_MESSAGE: &'static str = "yeah logging works as expected";
	const EXPECTED_NODE_NAME: &'static str = "THE_NODE";

	fn init_logger(directives: &str) {
		let _ = LoggerBuilder::new(directives).init().unwrap();
	}

	fn run_test_in_another_process(
		test_name: &str,
		test_body: impl FnOnce(),
	) -> Option<std::process::Output> {
		if env::var("RUN_FORKED_TEST").is_ok() {
			test_body();
			None
		} else {
			let output = Command::new(env::current_exe().unwrap())
				.arg(test_name)
				.env("RUN_FORKED_TEST", "1")
				.output()
				.unwrap();

			assert!(output.status.success());
			Some(output)
		}
	}

	#[test]
	fn test_logger_filters() {
		run_test_in_another_process("test_logger_filters", || {
			let test_directives =
				"grandpa=debug,sync=trace,client=warn,telemetry,something-with-dash=error";
			init_logger(&test_directives);

			tracing::dispatcher::get_default(|dispatcher| {
				let test_filter = |target, level| {
					struct DummyCallSite;
					impl Callsite for DummyCallSite {
						fn set_interest(&self, _: Interest) {}
						fn metadata(&self) -> &Metadata<'_> {
							unreachable!();
						}
					}

					let metadata = tracing::metadata!(
						name: "",
						target: target,
						level: level,
						fields: &[],
						callsite: &DummyCallSite,
						kind: Kind::SPAN,
					);

					dispatcher.enabled(&metadata)
				};

				assert!(test_filter("grandpa", Level::INFO));
				assert!(test_filter("grandpa", Level::DEBUG));
				assert!(!test_filter("grandpa", Level::TRACE));

				assert!(test_filter("sync", Level::TRACE));
				assert!(test_filter("client", Level::WARN));

				assert!(test_filter("telemetry", Level::TRACE));
				assert!(test_filter("something-with-dash", Level::ERROR));
			});
		});
	}

	/// This test ensures that using dash (`-`) in the target name in logs and directives actually
	/// work.
	#[test]
	fn dash_in_target_name_works() {
		let executable = env::current_exe().unwrap();
		let output = Command::new(executable)
			.env("ENABLE_LOGGING", "1")
			.args(&["--nocapture", "log_something_with_dash_target_name"])
			.output()
			.unwrap();

		let output = String::from_utf8(output.stderr).unwrap();
		assert!(output.contains(EXPECTED_LOG_MESSAGE));
	}

	/// This is not an actual test, it is used by the `dash_in_target_name_works` test.
	/// The given test will call the test executable and only execute this one test that
	/// only prints `EXPECTED_LOG_MESSAGE` through logging while using a target
	/// name that contains a dash. This ensures that target names with dashes work.
	#[test]
	fn log_something_with_dash_target_name() {
		if env::var("ENABLE_LOGGING").is_ok() {
			let test_directives = "test-target=info";
			let _guard = init_logger(&test_directives);

			log::info!(target: "test-target", "{}", EXPECTED_LOG_MESSAGE);
		}
	}

	#[test]
	fn prefix_in_log_lines() {
		let re = regex::Regex::new(&format!(
			r"^\d{{4}}-\d{{2}}-\d{{2}} \d{{2}}:\d{{2}}:\d{{2}} \[{}\] {}$",
			EXPECTED_NODE_NAME, EXPECTED_LOG_MESSAGE,
		))
		.unwrap();
		let executable = env::current_exe().unwrap();
		let output = Command::new(executable)
			.env("ENABLE_LOGGING", "1")
			.args(&["--nocapture", "prefix_in_log_lines_entrypoint"])
			.output()
			.unwrap();

		let output = String::from_utf8(output.stderr).unwrap();
		assert!(re.is_match(output.trim()), "Expected:\n{}\nGot:\n{}", re, output);
	}

	/// This is not an actual test, it is used by the `prefix_in_log_lines` test.
	/// The given test will call the test executable and only execute this one test that
	/// only prints a log line prefixed by the node name `EXPECTED_NODE_NAME`.
	#[test]
	fn prefix_in_log_lines_entrypoint() {
		if env::var("ENABLE_LOGGING").is_ok() {
			let _guard = init_logger("");
			prefix_in_log_lines_process();
		}
	}

	#[crate::logging::prefix_logs_with(EXPECTED_NODE_NAME)]
	fn prefix_in_log_lines_process() {
		log::info!("{}", EXPECTED_LOG_MESSAGE);
	}

	/// This is not an actual test, it is used by the `do_not_write_with_colors_on_tty` test.
	/// The given test will call the test executable and only execute this one test that
	/// only prints a log line with some colors in it.
	#[test]
	fn do_not_write_with_colors_on_tty_entrypoint() {
		if env::var("ENABLE_LOGGING").is_ok() {
			let _guard = init_logger("");
			log::info!("{}", console::style(EXPECTED_LOG_MESSAGE).yellow());
		}
	}

	#[test]
	fn do_not_write_with_colors_on_tty() {
		let re = regex::Regex::new(&format!(
			r"^\d{{4}}-\d{{2}}-\d{{2}} \d{{2}}:\d{{2}}:\d{{2}} {}$",
			EXPECTED_LOG_MESSAGE,
		))
		.unwrap();
		let executable = env::current_exe().unwrap();
		let output = Command::new(executable)
			.env("ENABLE_LOGGING", "1")
			.args(&["--nocapture", "do_not_write_with_colors_on_tty_entrypoint"])
			.output()
			.unwrap();

		let output = String::from_utf8(output.stderr).unwrap();
		assert!(re.is_match(output.trim()), "Expected:\n{}\nGot:\n{}", re, output);
	}

	#[test]
	fn log_max_level_is_set_properly() {
		fn run_test(rust_log: Option<String>, tracing_targets: Option<String>) -> String {
			let executable = env::current_exe().unwrap();
			let mut command = Command::new(executable);

			command
				.env("PRINT_MAX_LOG_LEVEL", "1")
				.args(&["--nocapture", "log_max_level_is_set_properly"]);

			if let Some(rust_log) = rust_log {
				command.env("RUST_LOG", rust_log);
			}

			if let Some(tracing_targets) = tracing_targets {
				command.env("TRACING_TARGETS", tracing_targets);
			}

			let output = command.output().unwrap();

			dbg!(String::from_utf8(output.stderr)).unwrap()
		}

		if env::var("PRINT_MAX_LOG_LEVEL").is_ok() {
			let mut builder = LoggerBuilder::new("");

			if let Ok(targets) = env::var("TRACING_TARGETS") {
				builder.with_profiling(crate::TracingReceiver::Log, targets);
			}

			builder.init().unwrap();

			eprint!("MAX_LOG_LEVEL={:?}", log::max_level());
		} else {
			assert_eq!("MAX_LOG_LEVEL=Info", run_test(None, None));
			assert_eq!("MAX_LOG_LEVEL=Trace", run_test(Some("test=trace".into()), None));
			assert_eq!("MAX_LOG_LEVEL=Debug", run_test(Some("test=debug".into()), None));
			assert_eq!("MAX_LOG_LEVEL=Trace", run_test(None, Some("test=info".into())));
		}
	}

	// This creates a bunch of threads and makes sure they start executing
	// a given callback almost exactly at the same time.
	fn run_on_many_threads(thread_count: usize, callback: impl Fn(usize) + 'static + Send + Clone) {
		let started_count = Arc::new(AtomicUsize::new(0));
		let barrier = Arc::new(AtomicBool::new(false));
		let threads: Vec<_> = (0..thread_count)
			.map(|nth_thread| {
				let started_count = started_count.clone();
				let barrier = barrier.clone();
				let callback = callback.clone();

				std::thread::spawn(move || {
					started_count.fetch_add(1, Ordering::SeqCst);
					while !barrier.load(Ordering::SeqCst) {
						std::thread::yield_now();
					}

					callback(nth_thread);
				})
			})
			.collect();

		while started_count.load(Ordering::SeqCst) != thread_count {
			std::thread::yield_now();
		}
		barrier.store(true, Ordering::SeqCst);

		for thread in threads {
			if let Err(error) = thread.join() {
				println!("error: failed to join thread: {:?}", error);
				unsafe { libc::abort() }
			}
		}
	}

	#[test]
	fn parallel_logs_from_multiple_threads_are_properly_gathered() {
		const THREAD_COUNT: usize = 128;
		const LOGS_PER_THREAD: usize = 1024;

		let output = run_test_in_another_process(
			"parallel_logs_from_multiple_threads_are_properly_gathered",
			|| {
				let builder = LoggerBuilder::new("");
				builder.init().unwrap();

				run_on_many_threads(THREAD_COUNT, |nth_thread| {
					for _ in 0..LOGS_PER_THREAD {
						info!("Thread <<{}>>", nth_thread);
					}
				});
			},
		);

		if let Some(output) = output {
			let stderr = String::from_utf8(output.stderr).unwrap();
			let mut count_per_thread = BTreeMap::new();
			for line in stderr.split("\n") {
				if let Some(index_s) = line.find("Thread <<") {
					let index_s = index_s + "Thread <<".len();
					let index_e = line.find(">>").unwrap();
					let nth_thread: usize = line[index_s..index_e].parse().unwrap();
					*count_per_thread.entry(nth_thread).or_insert(0) += 1;
				}
			}

			assert_eq!(count_per_thread.len(), THREAD_COUNT);
			for (_, count) in count_per_thread {
				assert_eq!(count, LOGS_PER_THREAD);
			}
		}
	}

	#[test]
	fn huge_single_line_log_is_properly_printed_out() {
		let mut line = String::new();
		line.push_str("$$START$$");
		for n in 0..16 * 1024 * 1024 {
			let ch = b'a' + (n as u8 % (b'z' - b'a'));
			line.push(char::from(ch));
		}
		line.push_str("$$END$$");

		let output =
			run_test_in_another_process("huge_single_line_log_is_properly_printed_out", || {
				let builder = LoggerBuilder::new("");
				builder.init().unwrap();
				info!("{}", line);
			});

		if let Some(output) = output {
			let stderr = String::from_utf8(output.stderr).unwrap();
			assert!(stderr.contains(&line));
		}
	}
}