🛈 Note: This is pre-release documentation for the upcoming tracing 0.2.0 ecosystem.

For the release documentation, please see docs.rs, instead.

tracing_subscriber/fmt/format/
json.rs

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
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
use super::{Format, FormatEvent, FormatFields, FormatTime, Writer};
use crate::{
    field::{RecordFields, VisitOutput},
    fmt::{
        fmt_subscriber::{FmtContext, FormattedFields},
        writer::WriteAdaptor,
    },
    registry::LookupSpan,
};
use serde::ser::{SerializeMap, Serializer as _};
use serde_json::Serializer;
use std::{
    collections::BTreeMap,
    fmt::{self, Write},
};
use tracing_core::{
    field::{self, Field},
    span::Record,
    Collect, Event,
};
use tracing_serde::AsSerde;

#[cfg(feature = "tracing-log")]
use tracing_log::NormalizeEvent;

/// Marker for [`Format`] that indicates that the newline-delimited JSON log
/// format should be used.
///
/// This formatter is intended for production use with systems where structured
/// logs are consumed as JSON by analysis and viewing tools. The JSON output is
/// not optimized for human readability; instead, it should be pretty-printed
/// using external JSON tools such as `jq`, or using a JSON log viewer.
///
/// # Example Output
///
/// <pre><font color="#4E9A06"><b>:;</b></font> <font color="#4E9A06">cargo</font> run --example fmt-json
/// <font color="#4E9A06"><b>    Finished</b></font> dev [unoptimized + debuginfo] target(s) in 0.08s
/// <font color="#4E9A06"><b>     Running</b></font> `target/debug/examples/fmt-json`
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821315Z&quot;,&quot;level&quot;:&quot;INFO&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;preparing to shave yaks&quot;,&quot;number_of_yaks&quot;:3},&quot;target&quot;:&quot;fmt_json&quot;}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821422Z&quot;,&quot;level&quot;:&quot;INFO&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;shaving yaks&quot;},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821495Z&quot;,&quot;level&quot;:&quot;TRACE&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;hello! I&apos;m gonna shave a yak&quot;,&quot;excitement&quot;:&quot;yay!&quot;},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;},{&quot;yak&quot;:1,&quot;name&quot;:&quot;shave&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821546Z&quot;,&quot;level&quot;:&quot;TRACE&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;yak shaved successfully&quot;},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;},{&quot;yak&quot;:1,&quot;name&quot;:&quot;shave&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821598Z&quot;,&quot;level&quot;:&quot;DEBUG&quot;,&quot;fields&quot;:{&quot;yak&quot;:1,&quot;shaved&quot;:true},&quot;target&quot;:&quot;yak_events&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821637Z&quot;,&quot;level&quot;:&quot;TRACE&quot;,&quot;fields&quot;:{&quot;yaks_shaved&quot;:1},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821684Z&quot;,&quot;level&quot;:&quot;TRACE&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;hello! I&apos;m gonna shave a yak&quot;,&quot;excitement&quot;:&quot;yay!&quot;},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;},{&quot;yak&quot;:2,&quot;name&quot;:&quot;shave&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821727Z&quot;,&quot;level&quot;:&quot;TRACE&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;yak shaved successfully&quot;},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;},{&quot;yak&quot;:2,&quot;name&quot;:&quot;shave&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821773Z&quot;,&quot;level&quot;:&quot;DEBUG&quot;,&quot;fields&quot;:{&quot;yak&quot;:2,&quot;shaved&quot;:true},&quot;target&quot;:&quot;yak_events&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821806Z&quot;,&quot;level&quot;:&quot;TRACE&quot;,&quot;fields&quot;:{&quot;yaks_shaved&quot;:2},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821909Z&quot;,&quot;level&quot;:&quot;TRACE&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;hello! I&apos;m gonna shave a yak&quot;,&quot;excitement&quot;:&quot;yay!&quot;},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;},{&quot;yak&quot;:3,&quot;name&quot;:&quot;shave&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.821956Z&quot;,&quot;level&quot;:&quot;WARN&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;could not locate yak&quot;},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;},{&quot;yak&quot;:3,&quot;name&quot;:&quot;shave&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.822006Z&quot;,&quot;level&quot;:&quot;DEBUG&quot;,&quot;fields&quot;:{&quot;yak&quot;:3,&quot;shaved&quot;:false},&quot;target&quot;:&quot;yak_events&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.822041Z&quot;,&quot;level&quot;:&quot;ERROR&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;failed to shave yak&quot;,&quot;yak&quot;:3,&quot;error&quot;:&quot;missing yak&quot;},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.822079Z&quot;,&quot;level&quot;:&quot;TRACE&quot;,&quot;fields&quot;:{&quot;yaks_shaved&quot;:2},&quot;target&quot;:&quot;fmt_json::yak_shave&quot;,&quot;spans&quot;:[{&quot;yaks&quot;:3,&quot;name&quot;:&quot;shaving_yaks&quot;}]}
/// {&quot;timestamp&quot;:&quot;2022-02-15T18:47:10.822117Z&quot;,&quot;level&quot;:&quot;INFO&quot;,&quot;fields&quot;:{&quot;message&quot;:&quot;yak shaving completed&quot;,&quot;all_yaks_shaved&quot;:false},&quot;target&quot;:&quot;fmt_json&quot;}
/// </pre>
///
/// # Options
///
/// This formatter exposes additional options to configure the structure of the
/// output JSON objects:
///
/// - [`Json::flatten_event`] can be used to enable flattening event fields into
///   the root
/// - [`Json::with_current_span`] can be used to control logging of the current
///   span
/// - [`Json::with_span_list`] can be used to control logging of the span list
///   object.
///
/// By default, event fields are not flattened, and both current span and span
/// list are logged.
///
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct Json {
    pub(crate) flatten_event: bool,
    pub(crate) display_current_span: bool,
    pub(crate) display_span_list: bool,
}

impl Json {
    /// If set to `true` event metadata will be flattened into the root object.
    pub fn flatten_event(&mut self, flatten_event: bool) {
        self.flatten_event = flatten_event;
    }

    /// If set to `false`, formatted events won't contain a field for the current span.
    pub fn with_current_span(&mut self, display_current_span: bool) {
        self.display_current_span = display_current_span;
    }

    /// If set to `false`, formatted events won't contain a list of all currently
    /// entered spans. Spans are logged in a list from root to leaf.
    pub fn with_span_list(&mut self, display_span_list: bool) {
        self.display_span_list = display_span_list;
    }
}

struct SerializableContext<'a, 'b, Span, N>(
    &'b crate::subscribe::Context<'a, Span>,
    std::marker::PhantomData<N>,
)
where
    Span: Collect + for<'lookup> crate::registry::LookupSpan<'lookup>,
    N: for<'writer> FormatFields<'writer> + 'static;

impl<'a, 'b, Span, N> serde::ser::Serialize for SerializableContext<'a, 'b, Span, N>
where
    Span: Collect + for<'lookup> crate::registry::LookupSpan<'lookup>,
    N: for<'writer> FormatFields<'writer> + 'static,
{
    fn serialize<Ser>(&self, serializer_o: Ser) -> Result<Ser::Ok, Ser::Error>
    where
        Ser: serde::ser::Serializer,
    {
        use serde::ser::SerializeSeq;
        let mut serializer = serializer_o.serialize_seq(None)?;

        if let Some(leaf_span) = self.0.lookup_current() {
            for span in leaf_span.scope().from_root() {
                serializer.serialize_element(&SerializableSpan(&span, self.1))?;
            }
        }

        serializer.end()
    }
}

struct SerializableSpan<'a, 'b, Span, N>(
    &'b crate::registry::SpanRef<'a, Span>,
    std::marker::PhantomData<N>,
)
where
    Span: for<'lookup> crate::registry::LookupSpan<'lookup>,
    N: for<'writer> FormatFields<'writer> + 'static;

impl<'a, 'b, Span, N> serde::ser::Serialize for SerializableSpan<'a, 'b, Span, N>
where
    Span: for<'lookup> crate::registry::LookupSpan<'lookup>,
    N: for<'writer> FormatFields<'writer> + 'static,
{
    fn serialize<Ser>(&self, serializer: Ser) -> Result<Ser::Ok, Ser::Error>
    where
        Ser: serde::ser::Serializer,
    {
        let mut serializer = serializer.serialize_map(None)?;

        let ext = self.0.extensions();
        let data = ext
            .get::<FormattedFields<N>>()
            .expect("Unable to find FormattedFields in extensions; this is a bug");

        // TODO: let's _not_ do this, but this resolves
        // https://github.com/tokio-rs/tracing/issues/391.
        // We should probably rework this to use a `serde_json::Value` or something
        // similar in a JSON-specific layer, but I'd (david)
        // rather have a uglier fix now rather than shipping broken JSON.
        match serde_json::from_str::<serde_json::Value>(data) {
            Ok(serde_json::Value::Object(fields)) => {
                for field in fields {
                    serializer.serialize_entry(&field.0, &field.1)?;
                }
            }
            // We have fields for this span which are valid JSON but not an object.
            // This is probably a bug, so panic if we're in debug mode
            Ok(_) if cfg!(debug_assertions) => panic!(
                "span '{}' had malformed fields! this is a bug.\n  error: invalid JSON object\n  fields: {:?}",
                self.0.metadata().name(),
                data
            ),
            // If we *aren't* in debug mode, it's probably best not to
            // crash the program, let's log the field found but also an
            // message saying it's type  is invalid
            Ok(value) => {
                serializer.serialize_entry("field", &value)?;
                serializer.serialize_entry("field_error", "field was no a valid object")?
            }
            // We have previously recorded fields for this span
            // should be valid JSON. However, they appear to *not*
            // be valid JSON. This is almost certainly a bug, so
            // panic if we're in debug mode
            Err(e) if cfg!(debug_assertions) => panic!(
                "span '{}' had malformed fields! this is a bug.\n  error: {}\n  fields: {:?}",
                self.0.metadata().name(),
                e,
                data
            ),
            // If we *aren't* in debug mode, it's probably best not
            // crash the program, but let's at least make sure it's clear
            // that the fields are not supposed to be missing.
            Err(e) => serializer.serialize_entry("field_error", &format!("{}", e))?,
        };
        serializer.serialize_entry("name", self.0.metadata().name())?;
        serializer.end()
    }
}

impl<C, N, T> FormatEvent<C, N> for Format<Json, T>
where
    C: Collect + for<'lookup> LookupSpan<'lookup>,
    N: for<'writer> FormatFields<'writer> + 'static,
    T: FormatTime,
{
    fn format_event(
        &self,
        ctx: &FmtContext<'_, C, N>,
        mut writer: Writer<'_>,
        event: &Event<'_>,
    ) -> fmt::Result
    where
        C: Collect + for<'a> LookupSpan<'a>,
    {
        let mut timestamp = String::new();
        self.timer.format_time(&mut Writer::new(&mut timestamp))?;

        #[cfg(feature = "tracing-log")]
        let normalized_meta = event.normalized_metadata();
        #[cfg(feature = "tracing-log")]
        let meta = normalized_meta.as_ref().unwrap_or_else(|| event.metadata());
        #[cfg(not(feature = "tracing-log"))]
        let meta = event.metadata();

        let mut visit = || {
            let mut serializer = Serializer::new(WriteAdaptor::new(&mut writer));

            let mut serializer = serializer.serialize_map(None)?;

            if self.display_timestamp {
                serializer.serialize_entry("timestamp", &timestamp)?;
            }

            if self.display_level {
                serializer.serialize_entry("level", &meta.level().as_serde())?;
            }

            let format_field_marker: std::marker::PhantomData<N> = std::marker::PhantomData;

            let current_span = if self.format.display_current_span || self.format.display_span_list
            {
                event
                    .parent()
                    .and_then(|id| ctx.span(id))
                    .or_else(|| ctx.lookup_current())
            } else {
                None
            };

            if self.format.flatten_event {
                let mut visitor = tracing_serde::SerdeMapVisitor::new(serializer);
                event.record(&mut visitor);

                serializer = visitor.take_serializer()?;
            } else {
                use tracing_serde::fields::AsMap;
                serializer.serialize_entry("fields", &event.field_map())?;
            };

            if self.display_target {
                serializer.serialize_entry("target", meta.target())?;
            }

            if self.display_filename {
                if let Some(filename) = meta.file() {
                    serializer.serialize_entry("filename", filename)?;
                }
            }

            if self.display_line_number {
                if let Some(line_number) = meta.line() {
                    serializer.serialize_entry("line_number", &line_number)?;
                }
            }

            if self.format.display_current_span {
                if let Some(ref span) = current_span {
                    serializer
                        .serialize_entry("span", &SerializableSpan(span, format_field_marker))
                        .unwrap_or(());
                }
            }

            if self.format.display_span_list && current_span.is_some() {
                serializer.serialize_entry(
                    "spans",
                    &SerializableContext(&ctx.ctx, format_field_marker),
                )?;
            }

            if self.display_thread_name {
                let current_thread = std::thread::current();
                match current_thread.name() {
                    Some(name) => {
                        serializer.serialize_entry("threadName", name)?;
                    }
                    // fall-back to thread id when name is absent and ids are not enabled
                    None if !self.display_thread_id => {
                        serializer
                            .serialize_entry("threadName", &format!("{:?}", current_thread.id()))?;
                    }
                    _ => {}
                }
            }

            if self.display_thread_id {
                serializer
                    .serialize_entry("threadId", &format!("{:?}", std::thread::current().id()))?;
            }

            serializer.end()
        };

        visit().map_err(|_| fmt::Error)?;
        writeln!(writer)
    }
}

impl Default for Json {
    fn default() -> Json {
        Json {
            flatten_event: false,
            display_current_span: true,
            display_span_list: true,
        }
    }
}

/// The JSON [`FormatFields`] implementation.
///
#[derive(Debug)]
pub struct JsonFields {
    // reserve the ability to add fields to this without causing a breaking
    // change in the future.
    _private: (),
}

impl JsonFields {
    /// Returns a new JSON [`FormatFields`] implementation.
    ///
    pub fn new() -> Self {
        Self { _private: () }
    }
}

impl Default for JsonFields {
    fn default() -> Self {
        Self::new()
    }
}

impl<'a> FormatFields<'a> for JsonFields {
    /// Format the provided `fields` to the provided `writer`, returning a result.
    fn format_fields<R: RecordFields>(&self, mut writer: Writer<'_>, fields: R) -> fmt::Result {
        let mut v = JsonVisitor::new(&mut writer);
        fields.record(&mut v);
        v.finish()
    }

    /// Record additional field(s) on an existing span.
    ///
    /// By default, this appends a space to the current set of fields if it is
    /// non-empty, and then calls `self.format_fields`. If different behavior is
    /// required, the default implementation of this method can be overridden.
    fn add_fields(
        &self,
        current: &'a mut FormattedFields<Self>,
        fields: &Record<'_>,
    ) -> fmt::Result {
        if current.is_empty() {
            // If there are no previously recorded fields, we can just reuse the
            // existing string.
            let mut writer = current.as_writer();
            let mut v = JsonVisitor::new(&mut writer);
            fields.record(&mut v);
            v.finish()?;
            return Ok(());
        }

        // If fields were previously recorded on this span, we need to parse
        // the current set of fields as JSON, add the new fields, and
        // re-serialize them. Otherwise, if we just appended the new fields
        // to a previously serialized JSON object, we would end up with
        // malformed JSON.
        //
        // XXX(eliza): this is far from efficient, but unfortunately, it is
        // necessary as long as the JSON formatter is implemented on top of
        // an interface that stores all formatted fields as strings.
        //
        // We should consider reimplementing the JSON formatter as a
        // separate layer, rather than a formatter for the `fmt` layer —
        // then, we could store fields as JSON values, and add to them
        // without having to parse and re-serialize.
        let mut new = String::new();
        let map: BTreeMap<&'_ str, serde_json::Value> =
            serde_json::from_str(current).map_err(|_| fmt::Error)?;
        let mut v = JsonVisitor::new(&mut new);
        v.values = map;
        fields.record(&mut v);
        v.finish()?;
        current.fields = new;

        Ok(())
    }
}

/// The [visitor] produced by [`JsonFields`]'s [`MakeVisitor`] implementation.
///
/// [visitor]: crate::field::Visit
/// [`MakeVisitor`]: crate::field::MakeVisitor
pub struct JsonVisitor<'a> {
    values: BTreeMap<&'a str, serde_json::Value>,
    writer: &'a mut dyn Write,
}

impl<'a> fmt::Debug for JsonVisitor<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_fmt(format_args!("JsonVisitor {{ values: {:?} }}", self.values))
    }
}

impl<'a> JsonVisitor<'a> {
    /// Returns a new default visitor that formats to the provided `writer`.
    ///
    /// # Arguments
    /// - `writer`: the writer to format to.
    /// - `is_empty`: whether or not any fields have been previously written to
    ///   that writer.
    pub fn new(writer: &'a mut dyn Write) -> Self {
        Self {
            values: BTreeMap::new(),
            writer,
        }
    }
}

impl<'a> crate::field::VisitFmt for JsonVisitor<'a> {
    fn writer(&mut self) -> &mut dyn fmt::Write {
        self.writer
    }
}

impl<'a> crate::field::VisitOutput<fmt::Result> for JsonVisitor<'a> {
    fn finish(self) -> fmt::Result {
        let inner = || {
            let mut serializer = Serializer::new(WriteAdaptor::new(self.writer));
            let mut ser_map = serializer.serialize_map(None)?;

            for (k, v) in self.values {
                ser_map.serialize_entry(k, &v)?;
            }

            ser_map.end()
        };

        if inner().is_err() {
            Err(fmt::Error)
        } else {
            Ok(())
        }
    }
}

impl<'a> field::Visit for JsonVisitor<'a> {
    /// Visit a double precision floating point value.
    fn record_f64(&mut self, field: &Field, value: f64) {
        self.values
            .insert(field.name(), serde_json::Value::from(value));
    }

    /// Visit a signed 64-bit integer value.
    fn record_i64(&mut self, field: &Field, value: i64) {
        self.values
            .insert(field.name(), serde_json::Value::from(value));
    }

    /// Visit an unsigned 64-bit integer value.
    fn record_u64(&mut self, field: &Field, value: u64) {
        self.values
            .insert(field.name(), serde_json::Value::from(value));
    }

    /// Visit a boolean value.
    fn record_bool(&mut self, field: &Field, value: bool) {
        self.values
            .insert(field.name(), serde_json::Value::from(value));
    }

    /// Visit a string value.
    fn record_str(&mut self, field: &Field, value: &str) {
        self.values
            .insert(field.name(), serde_json::Value::from(value));
    }

    fn record_bytes(&mut self, field: &Field, value: &[u8]) {
        self.values
            .insert(field.name(), serde_json::Value::from(value));
    }

    fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
        match field.name() {
            // Skip fields that are actually log metadata that have already been handled
            #[cfg(feature = "tracing-log")]
            name if name.starts_with("log.") => (),
            name if name.starts_with("r#") => {
                self.values
                    .insert(&name[2..], serde_json::Value::from(format!("{:?}", value)));
            }
            name => {
                self.values
                    .insert(name, serde_json::Value::from(format!("{:?}", value)));
            }
        };
    }
}
#[cfg(test)]
mod test {
    use super::*;
    use crate::fmt::{format::FmtSpan, test::MockMakeWriter, time::FormatTime, CollectorBuilder};

    use tracing::{self, collect::with_default};

    use std::fmt;
    use std::path::Path;

    struct MockTime;
    impl FormatTime for MockTime {
        fn format_time(&self, w: &mut Writer<'_>) -> fmt::Result {
            write!(w, "fake time")
        }
    }

    fn collector() -> CollectorBuilder<JsonFields, Format<Json>> {
        crate::fmt::CollectorBuilder::default().json()
    }

    #[test]
    fn json() {
        let expected =
        "{\"timestamp\":\"fake time\",\"level\":\"INFO\",\"span\":{\"answer\":42,\"name\":\"json_span\",\"number\":3,\"slice\":[97,98,99]},\"spans\":[{\"answer\":42,\"name\":\"json_span\",\"number\":3,\"slice\":[97,98,99]}],\"target\":\"tracing_subscriber::fmt::format::json::test\",\"fields\":{\"message\":\"some json test\"}}\n";
        let collector = collector()
            .flatten_event(false)
            .with_current_span(true)
            .with_span_list(true);
        test_json(expected, collector, || {
            let span = tracing::span!(
                tracing::Level::INFO,
                "json_span",
                answer = 42,
                number = 3,
                slice = &b"abc"[..]
            );
            let _guard = span.enter();
            tracing::info!("some json test");
        });
    }

    #[test]
    fn json_filename() {
        let current_path = Path::new("tracing-subscriber")
            .join("src")
            .join("fmt")
            .join("format")
            .join("json.rs")
            .to_str()
            .expect("path must be valid unicode")
            // escape windows backslashes
            .replace('\\', "\\\\");
        let expected =
            &format!("{}{}{}",
                    "{\"timestamp\":\"fake time\",\"level\":\"INFO\",\"span\":{\"answer\":42,\"name\":\"json_span\",\"number\":3},\"spans\":[{\"answer\":42,\"name\":\"json_span\",\"number\":3}],\"target\":\"tracing_subscriber::fmt::format::json::test\",\"filename\":\"",
                    current_path,
                    "\",\"fields\":{\"message\":\"some json test\"}}\n");
        let collector = collector()
            .flatten_event(false)
            .with_current_span(true)
            .with_file(true)
            .with_span_list(true);
        test_json(expected, collector, || {
            let span = tracing::span!(tracing::Level::INFO, "json_span", answer = 42, number = 3);
            let _guard = span.enter();
            tracing::info!("some json test");
        });
    }

    #[test]
    fn json_line_number() {
        let expected =
            "{\"timestamp\":\"fake time\",\"level\":\"INFO\",\"span\":{\"answer\":42,\"name\":\"json_span\",\"number\":3},\"spans\":[{\"answer\":42,\"name\":\"json_span\",\"number\":3}],\"target\":\"tracing_subscriber::fmt::format::json::test\",\"line_number\":42,\"fields\":{\"message\":\"some json test\"}}\n";
        let collector = collector()
            .flatten_event(false)
            .with_current_span(true)
            .with_line_number(true)
            .with_span_list(true);
        test_json_with_line_number(expected, collector, || {
            let span = tracing::span!(tracing::Level::INFO, "json_span", answer = 42, number = 3);
            let _guard = span.enter();
            tracing::info!("some json test");
        });
    }

    #[test]
    fn json_flattened_event() {
        let expected =
        "{\"timestamp\":\"fake time\",\"level\":\"INFO\",\"span\":{\"answer\":42,\"name\":\"json_span\",\"number\":3},\"spans\":[{\"answer\":42,\"name\":\"json_span\",\"number\":3}],\"target\":\"tracing_subscriber::fmt::format::json::test\",\"message\":\"some json test\"}\n";

        let collector = collector()
            .flatten_event(true)
            .with_current_span(true)
            .with_span_list(true);
        test_json(expected, collector, || {
            let span = tracing::span!(tracing::Level::INFO, "json_span", answer = 42, number = 3);
            let _guard = span.enter();
            tracing::info!("some json test");
        });
    }

    #[test]
    fn json_disabled_current_span_event() {
        let expected =
        "{\"timestamp\":\"fake time\",\"level\":\"INFO\",\"spans\":[{\"answer\":42,\"name\":\"json_span\",\"number\":3}],\"target\":\"tracing_subscriber::fmt::format::json::test\",\"fields\":{\"message\":\"some json test\"}}\n";
        let collector = collector()
            .flatten_event(false)
            .with_current_span(false)
            .with_span_list(true);
        test_json(expected, collector, || {
            let span = tracing::span!(tracing::Level::INFO, "json_span", answer = 42, number = 3);
            let _guard = span.enter();
            tracing::info!("some json test");
        });
    }

    #[test]
    fn json_disabled_span_list_event() {
        let expected =
        "{\"timestamp\":\"fake time\",\"level\":\"INFO\",\"span\":{\"answer\":42,\"name\":\"json_span\",\"number\":3},\"target\":\"tracing_subscriber::fmt::format::json::test\",\"fields\":{\"message\":\"some json test\"}}\n";
        let collector = collector()
            .flatten_event(false)
            .with_current_span(true)
            .with_span_list(false);
        test_json(expected, collector, || {
            let span = tracing::span!(tracing::Level::INFO, "json_span", answer = 42, number = 3);
            let _guard = span.enter();
            tracing::info!("some json test");
        });
    }

    #[test]
    fn json_nested_span() {
        let expected =
        "{\"timestamp\":\"fake time\",\"level\":\"INFO\",\"span\":{\"answer\":43,\"name\":\"nested_json_span\",\"number\":4},\"spans\":[{\"answer\":42,\"name\":\"json_span\",\"number\":3},{\"answer\":43,\"name\":\"nested_json_span\",\"number\":4}],\"target\":\"tracing_subscriber::fmt::format::json::test\",\"fields\":{\"message\":\"some json test\"}}\n";
        let collector = collector()
            .flatten_event(false)
            .with_current_span(true)
            .with_span_list(true);
        test_json(expected, collector, || {
            let span = tracing::span!(tracing::Level::INFO, "json_span", answer = 42, number = 3);
            let _guard = span.enter();
            let span = tracing::span!(
                tracing::Level::INFO,
                "nested_json_span",
                answer = 43,
                number = 4
            );
            let _guard = span.enter();
            tracing::info!("some json test");
        });
    }

    #[test]
    fn json_no_span() {
        let expected =
        "{\"timestamp\":\"fake time\",\"level\":\"INFO\",\"target\":\"tracing_subscriber::fmt::format::json::test\",\"fields\":{\"message\":\"some json test\"}}\n";
        let collector = collector()
            .flatten_event(false)
            .with_current_span(true)
            .with_span_list(true);
        test_json(expected, collector, || {
            tracing::info!("some json test");
        });
    }

    #[test]
    fn record_works() {
        // This test reproduces issue #707, where using `Span::record` causes
        // any events inside the span to be ignored.

        let buffer = MockMakeWriter::default();
        let subscriber = crate::fmt().json().with_writer(buffer.clone()).finish();

        with_default(subscriber, || {
            tracing::info!("an event outside the root span");
            assert_eq!(
                parse_as_json(&buffer)["fields"]["message"],
                "an event outside the root span"
            );

            let span = tracing::info_span!("the span", na = tracing::field::Empty);
            span.record("na", "value");
            let _enter = span.enter();

            tracing::info!("an event inside the root span");
            assert_eq!(
                parse_as_json(&buffer)["fields"]["message"],
                "an event inside the root span"
            );
        });
    }

    #[test]
    fn json_span_event_show_correct_context() {
        let buffer = MockMakeWriter::default();
        let subscriber = collector()
            .with_writer(buffer.clone())
            .flatten_event(false)
            .with_current_span(true)
            .with_span_list(false)
            .with_span_events(FmtSpan::FULL)
            .finish();

        with_default(subscriber, || {
            let context = "parent";
            let parent_span = tracing::info_span!("parent_span", context);

            let event = parse_as_json(&buffer);
            assert_eq!(event["fields"]["message"], "new");
            assert_eq!(event["span"]["context"], "parent");

            let _parent_enter = parent_span.enter();
            let event = parse_as_json(&buffer);
            assert_eq!(event["fields"]["message"], "enter");
            assert_eq!(event["span"]["context"], "parent");

            let context = "child";
            let child_span = tracing::info_span!("child_span", context);
            let event = parse_as_json(&buffer);
            assert_eq!(event["fields"]["message"], "new");
            assert_eq!(event["span"]["context"], "child");

            let _child_enter = child_span.enter();
            let event = parse_as_json(&buffer);
            assert_eq!(event["fields"]["message"], "enter");
            assert_eq!(event["span"]["context"], "child");

            drop(_child_enter);
            let event = parse_as_json(&buffer);
            assert_eq!(event["fields"]["message"], "exit");
            assert_eq!(event["span"]["context"], "child");

            drop(child_span);
            let event = parse_as_json(&buffer);
            assert_eq!(event["fields"]["message"], "close");
            assert_eq!(event["span"]["context"], "child");

            drop(_parent_enter);
            let event = parse_as_json(&buffer);
            assert_eq!(event["fields"]["message"], "exit");
            assert_eq!(event["span"]["context"], "parent");

            drop(parent_span);
            let event = parse_as_json(&buffer);
            assert_eq!(event["fields"]["message"], "close");
            assert_eq!(event["span"]["context"], "parent");
        });
    }

    #[test]
    fn json_span_event_with_no_fields() {
        // Check span events serialize correctly.
        // Discussion: https://github.com/tokio-rs/tracing/issues/829#issuecomment-661984255
        //
        let buffer = MockMakeWriter::default();
        let subscriber = collector()
            .with_writer(buffer.clone())
            .flatten_event(false)
            .with_current_span(false)
            .with_span_list(false)
            .with_span_events(FmtSpan::FULL)
            .finish();

        with_default(subscriber, || {
            let span = tracing::info_span!("valid_json");
            assert_eq!(parse_as_json(&buffer)["fields"]["message"], "new");

            let _enter = span.enter();
            assert_eq!(parse_as_json(&buffer)["fields"]["message"], "enter");

            drop(_enter);
            assert_eq!(parse_as_json(&buffer)["fields"]["message"], "exit");

            drop(span);
            assert_eq!(parse_as_json(&buffer)["fields"]["message"], "close");
        });
    }

    fn parse_as_json(buffer: &MockMakeWriter) -> serde_json::Value {
        let buf = String::from_utf8(buffer.buf().to_vec()).unwrap();
        let json = buf
            .lines()
            .last()
            .expect("expected at least one line to be written!");
        match serde_json::from_str(json) {
            Ok(v) => v,
            Err(e) => panic!(
                "assertion failed: JSON shouldn't be malformed\n  error: {}\n  json: {}",
                e, json
            ),
        }
    }

    fn test_json<T>(
        expected: &str,
        builder: crate::fmt::CollectorBuilder<JsonFields, Format<Json>>,
        producer: impl FnOnce() -> T,
    ) {
        let make_writer = MockMakeWriter::default();
        let collector = builder
            .with_writer(make_writer.clone())
            .with_timer(MockTime)
            .finish();

        with_default(collector, producer);

        let buf = make_writer.buf();
        let actual = std::str::from_utf8(&buf[..]).unwrap();
        assert_eq!(
            serde_json::from_str::<std::collections::HashMap<&str, serde_json::Value>>(expected)
                .unwrap(),
            serde_json::from_str(actual).unwrap()
        );
    }

    fn test_json_with_line_number<T>(
        expected: &str,
        builder: crate::fmt::CollectorBuilder<JsonFields, Format<Json>>,
        producer: impl FnOnce() -> T,
    ) {
        let make_writer = MockMakeWriter::default();
        let collector = builder
            .with_writer(make_writer.clone())
            .with_timer(MockTime)
            .finish();

        with_default(collector, producer);

        let buf = make_writer.buf();
        let actual = std::str::from_utf8(&buf[..]).unwrap();
        let mut expected =
            serde_json::from_str::<std::collections::HashMap<&str, serde_json::Value>>(expected)
                .unwrap();
        let expect_line_number = expected.remove("line_number").is_some();
        let mut actual: std::collections::HashMap<&str, serde_json::Value> =
            serde_json::from_str(actual).unwrap();
        let line_number = actual.remove("line_number");
        if expect_line_number {
            assert_eq!(line_number.map(|x| x.is_number()), Some(true));
        } else {
            assert!(line_number.is_none());
        }
        assert_eq!(actual, expected);
    }
}