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
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
//! The Value enum, a loosely typed way of representing any valid JSON value.
//!
//! # Constructing JSON
//!
//! Serde JSON provides a [`json!` macro][macro] to build `serde_json::Value`
//! objects with very natural JSON syntax.
//!
//! ```
//! use serde_json::json;
//!
//! fn main() {
//!     // The type of `john` is `serde_json::Value`
//!     let john = json!({
//!         "name": "John Doe",
//!         "age": 43,
//!         "phones": [
//!             "+44 1234567",
//!             "+44 2345678"
//!         ]
//!     });
//!
//!     println!("first phone number: {}", john["phones"][0]);
//!
//!     // Convert to a string of JSON and print it out
//!     println!("{}", john.to_string());
//! }
//! ```
//!
//! The `Value::to_string()` function converts a `serde_json::Value` into a
//! `String` of JSON text.
//!
//! One neat thing about the `json!` macro is that variables and expressions can
//! be interpolated directly into the JSON value as you are building it. Serde
//! will check at compile time that the value you are interpolating is able to
//! be represented as JSON.
//!
//! ```
//! # use serde_json::json;
//! #
//! # fn random_phone() -> u16 { 0 }
//! #
//! let full_name = "John Doe";
//! let age_last_year = 42;
//!
//! // The type of `john` is `serde_json::Value`
//! let john = json!({
//!     "name": full_name,
//!     "age": age_last_year + 1,
//!     "phones": [
//!         format!("+44 {}", random_phone())
//!     ]
//! });
//! ```
//!
//! A string of JSON data can be parsed into a `serde_json::Value` by the
//! [`serde_json::from_str`][from_str] function. There is also
//! [`from_slice`][from_slice] for parsing from a byte slice `&[u8]` and
//! [`from_reader`][from_reader] for parsing from any `io::Read` like a File or
//! a TCP stream.
//!
//! ```
//! use serde_json::{json, Value, Error};
//!
//! fn untyped_example() -> Result<(), Error> {
//!     // Some JSON input data as a &str. Maybe this comes from the user.
//!     let data = r#"
//!         {
//!             "name": "John Doe",
//!             "age": 43,
//!             "phones": [
//!                 "+44 1234567",
//!                 "+44 2345678"
//!             ]
//!         }"#;
//!
//!     // Parse the string of data into serde_json::Value.
//!     let v: Value = serde_json::from_str(data)?;
//!
//!     // Access parts of the data by indexing with square brackets.
//!     println!("Please call {} at the number {}", v["name"], v["phones"][0]);
//!
//!     Ok(())
//! }
//! #
//! # untyped_example().unwrap();
//! ```
//!
//! [macro]: https://docs.serde.rs/serde_json/macro.json.html
//! [from_str]: https://docs.serde.rs/serde_json/de/fn.from_str.html
//! [from_slice]: https://docs.serde.rs/serde_json/de/fn.from_slice.html
//! [from_reader]: https://docs.serde.rs/serde_json/de/fn.from_reader.html

use self::ser::Serializer;
use crate::error::Error;
use crate::io;
use crate::lib::*;
use serde::de::DeserializeOwned;
use serde::ser::Serialize;

pub use self::index::Index;
pub use crate::map::Map;
pub use crate::number::Number;

#[cfg(feature = "raw_value")]
pub use crate::raw::RawValue;

/// Represents any valid JSON value.
///
/// See the `serde_json::value` module documentation for usage examples.
#[derive(Clone, PartialEq)]
pub enum Value {
    /// Represents a JSON null value.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!(null);
    /// ```
    Null,

    /// Represents a JSON boolean.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!(true);
    /// ```
    Bool(bool),

    /// Represents a JSON number, whether integer or floating point.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!(12.5);
    /// ```
    Number(Number),

    /// Represents a JSON string.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!("a string");
    /// ```
    String(String),

    /// Represents a JSON array.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!(["an", "array"]);
    /// ```
    Array(Vec<Value>),

    /// Represents a JSON object.
    ///
    /// By default the map is backed by a BTreeMap. Enable the `preserve_order`
    /// feature of serde_json to use IndexMap instead, which preserves
    /// entries in the order they are inserted into the map. In particular, this
    /// allows JSON data to be deserialized into a Value and serialized to a
    /// string while retaining the order of map keys in the input.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "an": "object" });
    /// ```
    Object(Map<String, Value>),
}

impl Debug for Value {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Value::Null => formatter.debug_tuple("Null").finish(),
            Value::Bool(v) => formatter.debug_tuple("Bool").field(&v).finish(),
            Value::Number(ref v) => Debug::fmt(v, formatter),
            Value::String(ref v) => formatter.debug_tuple("String").field(v).finish(),
            Value::Array(ref v) => formatter.debug_tuple("Array").field(v).finish(),
            Value::Object(ref v) => formatter.debug_tuple("Object").field(v).finish(),
        }
    }
}

struct WriterFormatter<'a, 'b: 'a> {
    inner: &'a mut fmt::Formatter<'b>,
}

impl<'a, 'b> io::Write for WriterFormatter<'a, 'b> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        fn io_error<E>(_: E) -> io::Error {
            // Error value does not matter because fmt::Display impl below just
            // maps it to fmt::Error
            io::Error::new(io::ErrorKind::Other, "fmt error")
        }
        let s = tri!(str::from_utf8(buf).map_err(io_error));
        tri!(self.inner.write_str(s).map_err(io_error));
        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

impl fmt::Display for Value {
    /// Display a JSON value as a string.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let json = json!({ "city": "London", "street": "10 Downing Street" });
    ///
    /// // Compact format:
    /// //
    /// // {"city":"London","street":"10 Downing Street"}
    /// let compact = format!("{}", json);
    /// assert_eq!(compact,
    ///     "{\"city\":\"London\",\"street\":\"10 Downing Street\"}");
    ///
    /// // Pretty format:
    /// //
    /// // {
    /// //   "city": "London",
    /// //   "street": "10 Downing Street"
    /// // }
    /// let pretty = format!("{:#}", json);
    /// assert_eq!(pretty,
    ///     "{\n  \"city\": \"London\",\n  \"street\": \"10 Downing Street\"\n}");
    /// ```
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let alternate = f.alternate();
        let mut wr = WriterFormatter { inner: f };
        if alternate {
            // {:#}
            super::ser::to_writer_pretty(&mut wr, self).map_err(|_| fmt::Error)
        } else {
            // {}
            super::ser::to_writer(&mut wr, self).map_err(|_| fmt::Error)
        }
    }
}

fn parse_index(s: &str) -> Option<usize> {
    if s.starts_with('+') || (s.starts_with('0') && s.len() != 1) {
        return None;
    }
    s.parse().ok()
}

impl Value {
    /// Index into a JSON array or map. A string index can be used to access a
    /// value in a map, and a usize index can be used to access an element of an
    /// array.
    ///
    /// Returns `None` if the type of `self` does not match the type of the
    /// index, for example if the index is a string and `self` is an array or a
    /// number. Also returns `None` if the given key does not exist in the map
    /// or the given index is not within the bounds of the array.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let object = json!({ "A": 65, "B": 66, "C": 67 });
    /// assert_eq!(*object.get("A").unwrap(), json!(65));
    ///
    /// let array = json!([ "A", "B", "C" ]);
    /// assert_eq!(*array.get(2).unwrap(), json!("C"));
    ///
    /// assert_eq!(array.get("A"), None);
    /// ```
    ///
    /// Square brackets can also be used to index into a value in a more concise
    /// way. This returns `Value::Null` in cases where `get` would have returned
    /// `None`.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let object = json!({
    ///     "A": ["a", "á", "à"],
    ///     "B": ["b", "b́"],
    ///     "C": ["c", "ć", "ć̣", "ḉ"],
    /// });
    /// assert_eq!(object["B"][0], json!("b"));
    ///
    /// assert_eq!(object["D"], json!(null));
    /// assert_eq!(object[0]["x"]["y"]["z"], json!(null));
    /// ```
    pub fn get<I: Index>(&self, index: I) -> Option<&Value> {
        index.index_into(self)
    }

    /// Mutably index into a JSON array or map. A string index can be used to
    /// access a value in a map, and a usize index can be used to access an
    /// element of an array.
    ///
    /// Returns `None` if the type of `self` does not match the type of the
    /// index, for example if the index is a string and `self` is an array or a
    /// number. Also returns `None` if the given key does not exist in the map
    /// or the given index is not within the bounds of the array.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let mut object = json!({ "A": 65, "B": 66, "C": 67 });
    /// *object.get_mut("A").unwrap() = json!(69);
    ///
    /// let mut array = json!([ "A", "B", "C" ]);
    /// *array.get_mut(2).unwrap() = json!("D");
    /// ```
    pub fn get_mut<I: Index>(&mut self, index: I) -> Option<&mut Value> {
        index.index_into_mut(self)
    }

    /// Returns true if the `Value` is an Object. Returns false otherwise.
    ///
    /// For any Value on which `is_object` returns true, `as_object` and
    /// `as_object_mut` are guaranteed to return the map representation of the
    /// object.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let obj = json!({ "a": { "nested": true }, "b": ["an", "array"] });
    ///
    /// assert!(obj.is_object());
    /// assert!(obj["a"].is_object());
    ///
    /// // array, not an object
    /// assert!(!obj["b"].is_object());
    /// ```
    pub fn is_object(&self) -> bool {
        self.as_object().is_some()
    }

    /// If the `Value` is an Object, returns the associated Map. Returns None
    /// otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": { "nested": true }, "b": ["an", "array"] });
    ///
    /// // The length of `{"nested": true}` is 1 entry.
    /// assert_eq!(v["a"].as_object().unwrap().len(), 1);
    ///
    /// // The array `["an", "array"]` is not an object.
    /// assert_eq!(v["b"].as_object(), None);
    /// ```
    pub fn as_object(&self) -> Option<&Map<String, Value>> {
        match *self {
            Value::Object(ref map) => Some(map),
            _ => None,
        }
    }

    /// If the `Value` is an Object, returns the associated mutable Map.
    /// Returns None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let mut v = json!({ "a": { "nested": true } });
    ///
    /// v["a"].as_object_mut().unwrap().clear();
    /// assert_eq!(v, json!({ "a": {} }));
    /// ```
    pub fn as_object_mut(&mut self) -> Option<&mut Map<String, Value>> {
        match *self {
            Value::Object(ref mut map) => Some(map),
            _ => None,
        }
    }

    /// Returns true if the `Value` is an Array. Returns false otherwise.
    ///
    /// For any Value on which `is_array` returns true, `as_array` and
    /// `as_array_mut` are guaranteed to return the vector representing the
    /// array.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let obj = json!({ "a": ["an", "array"], "b": { "an": "object" } });
    ///
    /// assert!(obj["a"].is_array());
    ///
    /// // an object, not an array
    /// assert!(!obj["b"].is_array());
    /// ```
    pub fn is_array(&self) -> bool {
        self.as_array().is_some()
    }

    /// If the `Value` is an Array, returns the associated vector. Returns None
    /// otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": ["an", "array"], "b": { "an": "object" } });
    ///
    /// // The length of `["an", "array"]` is 2 elements.
    /// assert_eq!(v["a"].as_array().unwrap().len(), 2);
    ///
    /// // The object `{"an": "object"}` is not an array.
    /// assert_eq!(v["b"].as_array(), None);
    /// ```
    pub fn as_array(&self) -> Option<&Vec<Value>> {
        match *self {
            Value::Array(ref array) => Some(&*array),
            _ => None,
        }
    }

    /// If the `Value` is an Array, returns the associated mutable vector.
    /// Returns None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let mut v = json!({ "a": ["an", "array"] });
    ///
    /// v["a"].as_array_mut().unwrap().clear();
    /// assert_eq!(v, json!({ "a": [] }));
    /// ```
    pub fn as_array_mut(&mut self) -> Option<&mut Vec<Value>> {
        match *self {
            Value::Array(ref mut list) => Some(list),
            _ => None,
        }
    }

    /// Returns true if the `Value` is a String. Returns false otherwise.
    ///
    /// For any Value on which `is_string` returns true, `as_str` is guaranteed
    /// to return the string slice.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": "some string", "b": false });
    ///
    /// assert!(v["a"].is_string());
    ///
    /// // The boolean `false` is not a string.
    /// assert!(!v["b"].is_string());
    /// ```
    pub fn is_string(&self) -> bool {
        self.as_str().is_some()
    }

    /// If the `Value` is a String, returns the associated str. Returns None
    /// otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": "some string", "b": false });
    ///
    /// assert_eq!(v["a"].as_str(), Some("some string"));
    ///
    /// // The boolean `false` is not a string.
    /// assert_eq!(v["b"].as_str(), None);
    ///
    /// // JSON values are printed in JSON representation, so strings are in quotes.
    /// //
    /// //    The value is: "some string"
    /// println!("The value is: {}", v["a"]);
    ///
    /// // Rust strings are printed without quotes.
    /// //
    /// //    The value is: some string
    /// println!("The value is: {}", v["a"].as_str().unwrap());
    /// ```
    pub fn as_str(&self) -> Option<&str> {
        match *self {
            Value::String(ref s) => Some(s),
            _ => None,
        }
    }

    /// Returns true if the `Value` is a Number. Returns false otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 1, "b": "2" });
    ///
    /// assert!(v["a"].is_number());
    ///
    /// // The string `"2"` is a string, not a number.
    /// assert!(!v["b"].is_number());
    /// ```
    pub fn is_number(&self) -> bool {
        match *self {
            Value::Number(_) => true,
            _ => false,
        }
    }

    /// Returns true if the `Value` is an integer between `i64::MIN` and
    /// `i64::MAX`.
    ///
    /// For any Value on which `is_i64` returns true, `as_i64` is guaranteed to
    /// return the integer value.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let big = i64::max_value() as u64 + 10;
    /// let v = json!({ "a": 64, "b": big, "c": 256.0 });
    ///
    /// assert!(v["a"].is_i64());
    ///
    /// // Greater than i64::MAX.
    /// assert!(!v["b"].is_i64());
    ///
    /// // Numbers with a decimal point are not considered integers.
    /// assert!(!v["c"].is_i64());
    /// ```
    pub fn is_i64(&self) -> bool {
        match *self {
            Value::Number(ref n) => n.is_i64(),
            _ => false,
        }
    }

    /// Returns true if the `Value` is an integer between zero and `u64::MAX`.
    ///
    /// For any Value on which `is_u64` returns true, `as_u64` is guaranteed to
    /// return the integer value.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 64, "b": -64, "c": 256.0 });
    ///
    /// assert!(v["a"].is_u64());
    ///
    /// // Negative integer.
    /// assert!(!v["b"].is_u64());
    ///
    /// // Numbers with a decimal point are not considered integers.
    /// assert!(!v["c"].is_u64());
    /// ```
    pub fn is_u64(&self) -> bool {
        match *self {
            Value::Number(ref n) => n.is_u64(),
            _ => false,
        }
    }

    /// Returns true if the `Value` is a number that can be represented by f64.
    ///
    /// For any Value on which `is_f64` returns true, `as_f64` is guaranteed to
    /// return the floating point value.
    ///
    /// Currently this function returns true if and only if both `is_i64` and
    /// `is_u64` return false but this is not a guarantee in the future.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 256.0, "b": 64, "c": -64 });
    ///
    /// assert!(v["a"].is_f64());
    ///
    /// // Integers.
    /// assert!(!v["b"].is_f64());
    /// assert!(!v["c"].is_f64());
    /// ```
    pub fn is_f64(&self) -> bool {
        match *self {
            Value::Number(ref n) => n.is_f64(),
            _ => false,
        }
    }

    /// If the `Value` is an integer, represent it as i64 if possible. Returns
    /// None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let big = i64::max_value() as u64 + 10;
    /// let v = json!({ "a": 64, "b": big, "c": 256.0 });
    ///
    /// assert_eq!(v["a"].as_i64(), Some(64));
    /// assert_eq!(v["b"].as_i64(), None);
    /// assert_eq!(v["c"].as_i64(), None);
    /// ```
    pub fn as_i64(&self) -> Option<i64> {
        match *self {
            Value::Number(ref n) => n.as_i64(),
            _ => None,
        }
    }

    /// If the `Value` is an integer, represent it as u64 if possible. Returns
    /// None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 64, "b": -64, "c": 256.0 });
    ///
    /// assert_eq!(v["a"].as_u64(), Some(64));
    /// assert_eq!(v["b"].as_u64(), None);
    /// assert_eq!(v["c"].as_u64(), None);
    /// ```
    pub fn as_u64(&self) -> Option<u64> {
        match *self {
            Value::Number(ref n) => n.as_u64(),
            _ => None,
        }
    }

    /// If the `Value` is a number, represent it as f64 if possible. Returns
    /// None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 256.0, "b": 64, "c": -64 });
    ///
    /// assert_eq!(v["a"].as_f64(), Some(256.0));
    /// assert_eq!(v["b"].as_f64(), Some(64.0));
    /// assert_eq!(v["c"].as_f64(), Some(-64.0));
    /// ```
    pub fn as_f64(&self) -> Option<f64> {
        match *self {
            Value::Number(ref n) => n.as_f64(),
            _ => None,
        }
    }

    /// Returns true if the `Value` is a Boolean. Returns false otherwise.
    ///
    /// For any Value on which `is_boolean` returns true, `as_bool` is
    /// guaranteed to return the boolean value.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": false, "b": "false" });
    ///
    /// assert!(v["a"].is_boolean());
    ///
    /// // The string `"false"` is a string, not a boolean.
    /// assert!(!v["b"].is_boolean());
    /// ```
    pub fn is_boolean(&self) -> bool {
        self.as_bool().is_some()
    }

    /// If the `Value` is a Boolean, returns the associated bool. Returns None
    /// otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": false, "b": "false" });
    ///
    /// assert_eq!(v["a"].as_bool(), Some(false));
    ///
    /// // The string `"false"` is a string, not a boolean.
    /// assert_eq!(v["b"].as_bool(), None);
    /// ```
    pub fn as_bool(&self) -> Option<bool> {
        match *self {
            Value::Bool(b) => Some(b),
            _ => None,
        }
    }

    /// Returns true if the `Value` is a Null. Returns false otherwise.
    ///
    /// For any Value on which `is_null` returns true, `as_null` is guaranteed
    /// to return `Some(())`.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": null, "b": false });
    ///
    /// assert!(v["a"].is_null());
    ///
    /// // The boolean `false` is not null.
    /// assert!(!v["b"].is_null());
    /// ```
    pub fn is_null(&self) -> bool {
        self.as_null().is_some()
    }

    /// If the `Value` is a Null, returns (). Returns None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": null, "b": false });
    ///
    /// assert_eq!(v["a"].as_null(), Some(()));
    ///
    /// // The boolean `false` is not null.
    /// assert_eq!(v["b"].as_null(), None);
    /// ```
    pub fn as_null(&self) -> Option<()> {
        match *self {
            Value::Null => Some(()),
            _ => None,
        }
    }

    /// Looks up a value by a JSON Pointer.
    ///
    /// JSON Pointer defines a string syntax for identifying a specific value
    /// within a JavaScript Object Notation (JSON) document.
    ///
    /// A Pointer is a Unicode string with the reference tokens separated by `/`.
    /// Inside tokens `/` is replaced by `~1` and `~` is replaced by `~0`. The
    /// addressed value is returned and if there is no such value `None` is
    /// returned.
    ///
    /// For more information read [RFC6901](https://tools.ietf.org/html/rfc6901).
    ///
    /// # Examples
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let data = json!({
    ///     "x": {
    ///         "y": ["z", "zz"]
    ///     }
    /// });
    ///
    /// assert_eq!(data.pointer("/x/y/1").unwrap(), &json!("zz"));
    /// assert_eq!(data.pointer("/a/b/c"), None);
    /// ```
    pub fn pointer(&self, pointer: &str) -> Option<&Value> {
        if pointer == "" {
            return Some(self);
        }
        if !pointer.starts_with('/') {
            return None;
        }
        let tokens = pointer
            .split('/')
            .skip(1)
            .map(|x| x.replace("~1", "/").replace("~0", "~"));
        let mut target = self;

        for token in tokens {
            let target_opt = match *target {
                Value::Object(ref map) => map.get(&token),
                Value::Array(ref list) => parse_index(&token).and_then(|x| list.get(x)),
                _ => return None,
            };
            if let Some(t) = target_opt {
                target = t;
            } else {
                return None;
            }
        }
        Some(target)
    }

    /// Looks up a value by a JSON Pointer and returns a mutable reference to
    /// that value.
    ///
    /// JSON Pointer defines a string syntax for identifying a specific value
    /// within a JavaScript Object Notation (JSON) document.
    ///
    /// A Pointer is a Unicode string with the reference tokens separated by `/`.
    /// Inside tokens `/` is replaced by `~1` and `~` is replaced by `~0`. The
    /// addressed value is returned and if there is no such value `None` is
    /// returned.
    ///
    /// For more information read [RFC6901](https://tools.ietf.org/html/rfc6901).
    ///
    /// # Example of Use
    ///
    /// ```
    /// use serde_json::Value;
    ///
    /// fn main() {
    ///     let s = r#"{"x": 1.0, "y": 2.0}"#;
    ///     let mut value: Value = serde_json::from_str(s).unwrap();
    ///
    ///     // Check value using read-only pointer
    ///     assert_eq!(value.pointer("/x"), Some(&1.0.into()));
    ///     // Change value with direct assignment
    ///     *value.pointer_mut("/x").unwrap() = 1.5.into();
    ///     // Check that new value was written
    ///     assert_eq!(value.pointer("/x"), Some(&1.5.into()));
    ///     // Or change the value only if it exists
    ///     value.pointer_mut("/x").map(|v| *v = 1.5.into());
    ///
    ///     // "Steal" ownership of a value. Can replace with any valid Value.
    ///     let old_x = value.pointer_mut("/x").map(Value::take).unwrap();
    ///     assert_eq!(old_x, 1.5);
    ///     assert_eq!(value.pointer("/x").unwrap(), &Value::Null);
    /// }
    /// ```
    pub fn pointer_mut(&mut self, pointer: &str) -> Option<&mut Value> {
        if pointer == "" {
            return Some(self);
        }
        if !pointer.starts_with('/') {
            return None;
        }
        let tokens = pointer
            .split('/')
            .skip(1)
            .map(|x| x.replace("~1", "/").replace("~0", "~"));
        let mut target = self;

        for token in tokens {
            // borrow checker gets confused about `target` being mutably borrowed too many times because of the loop
            // this once-per-loop binding makes the scope clearer and circumvents the error
            let target_once = target;
            let target_opt = match *target_once {
                Value::Object(ref mut map) => map.get_mut(&token),
                Value::Array(ref mut list) => {
                    parse_index(&token).and_then(move |x| list.get_mut(x))
                }
                _ => return None,
            };
            if let Some(t) = target_opt {
                target = t;
            } else {
                return None;
            }
        }
        Some(target)
    }

    /// Takes the value out of the `Value`, leaving a `Null` in its place.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let mut v = json!({ "x": "y" });
    /// assert_eq!(v["x"].take(), json!("y"));
    /// assert_eq!(v, json!({ "x": null }));
    /// ```
    pub fn take(&mut self) -> Value {
        mem::replace(self, Value::Null)
    }
}

/// The default value is `Value::Null`.
///
/// This is useful for handling omitted `Value` fields when deserializing.
///
/// # Examples
///
/// ```
/// # use serde::Deserialize;
/// use serde_json::Value;
///
/// #[derive(Deserialize)]
/// struct Settings {
///     level: i32,
///     #[serde(default)]
///     extras: Value,
/// }
///
/// # fn try_main() -> Result<(), serde_json::Error> {
/// let data = r#" { "level": 42 } "#;
/// let s: Settings = serde_json::from_str(data)?;
///
/// assert_eq!(s.level, 42);
/// assert_eq!(s.extras, Value::Null);
/// #
/// #     Ok(())
/// # }
/// #
/// # try_main().unwrap()
/// ```
impl Default for Value {
    fn default() -> Value {
        Value::Null
    }
}

mod de;
mod from;
mod index;
mod partial_eq;
mod ser;

/// Convert a `T` into `serde_json::Value` which is an enum that can represent
/// any valid JSON data.
///
/// # Example
///
/// ```
/// use serde::Serialize;
/// use serde_json::json;
///
/// use std::error::Error;
///
/// #[derive(Serialize)]
/// struct User {
///     fingerprint: String,
///     location: String,
/// }
///
/// fn compare_json_values() -> Result<(), Box<Error>> {
///     let u = User {
///         fingerprint: "0xF9BA143B95FF6D82".to_owned(),
///         location: "Menlo Park, CA".to_owned(),
///     };
///
///     // The type of `expected` is `serde_json::Value`
///     let expected = json!({
///         "fingerprint": "0xF9BA143B95FF6D82",
///         "location": "Menlo Park, CA",
///     });
///
///     let v = serde_json::to_value(u).unwrap();
///     assert_eq!(v, expected);
///
///     Ok(())
/// }
/// #
/// # compare_json_values().unwrap();
/// ```
///
/// # Errors
///
/// This conversion can fail if `T`'s implementation of `Serialize` decides to
/// fail, or if `T` contains a map with non-string keys.
///
/// ```
/// use std::collections::BTreeMap;
///
/// fn main() {
///     // The keys in this map are vectors, not strings.
///     let mut map = BTreeMap::new();
///     map.insert(vec![32, 64], "x86");
///
///     println!("{}", serde_json::to_value(map).unwrap_err());
/// }
/// ```
// Taking by value is more friendly to iterator adapters, option and result
// consumers, etc. See https://github.com/serde-rs/json/pull/149.
pub fn to_value<T>(value: T) -> Result<Value, Error>
where
    T: Serialize,
{
    value.serialize(Serializer)
}

/// Interpret a `serde_json::Value` as an instance of type `T`.
///
/// # Example
///
/// ```
/// use serde::Deserialize;
/// use serde_json::json;
///
/// #[derive(Deserialize, Debug)]
/// struct User {
///     fingerprint: String,
///     location: String,
/// }
///
/// fn main() {
///     // The type of `j` is `serde_json::Value`
///     let j = json!({
///         "fingerprint": "0xF9BA143B95FF6D82",
///         "location": "Menlo Park, CA"
///     });
///
///     let u: User = serde_json::from_value(j).unwrap();
///     println!("{:#?}", u);
/// }
/// ```
///
/// # Errors
///
/// This conversion can fail if the structure of the Value does not match the
/// structure expected by `T`, for example if `T` is a struct type but the Value
/// contains something other than a JSON map. It can also fail if the structure
/// is correct but `T`'s implementation of `Deserialize` decides that something
/// is wrong with the data, for example required struct fields are missing from
/// the JSON map or some number is too big to fit in the expected primitive
/// type.
pub fn from_value<T>(value: Value) -> Result<T, Error>
where
    T: DeserializeOwned,
{
    T::deserialize(value)
}