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 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280
//! Generic deserialization framework. #[cfg(feature = "std")] use std::error; #[cfg(not(feature = "std"))] use error; #[cfg(all(not(feature = "std"), feature = "collections"))] use collections::{String, Vec}; use core::fmt::{self, Display}; use core::marker::PhantomData; /////////////////////////////////////////////////////////////////////////////// pub mod impls; pub mod value; mod from_primitive; // Helpers used by generated code. Not public API. #[doc(hidden)] pub mod private; /////////////////////////////////////////////////////////////////////////////// /// The `Error` trait allows `Deserialize` implementations to create descriptive /// error messages belonging to the `Deserializer` against which they are /// currently running. /// /// Every `Deserializer` declares an `Error` type that encompasses both /// general-purpose deserialization errors as well as errors specific to the /// particular deserialization format. For example the `Error` type of /// `serde_json` can represent errors like an invalid JSON escape sequence or an /// unterminated string literal, in addition to the error cases that are part of /// this trait. /// /// Most deserializers should only need to provide the `Error::custom` method /// and inherit the default behavior for the other methods. pub trait Error: Sized + error::Error { /// Raised when there is general error when deserializing a type. fn custom<T: Display>(msg: T) -> Self; /// Raised when a `Deserialize` receives a type different from what it was /// expecting. /// /// The `unexp` argument provides information about what type was received. /// This is the type that was present in the input file or other source data /// of the Deserializer. /// /// The `exp` argument provides information about what type was being /// expected. This is the type that is written in the program. /// /// For example if we try to deserialize a String out of a JSON file /// containing an integer, the unexpected type is the integer and the /// expected type is the string. fn invalid_type(unexp: Unexpected, exp: &Expected) -> Self { struct InvalidType<'a> { unexp: Unexpected<'a>, exp: &'a Expected, } impl<'a> Display for InvalidType<'a> { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { write!(formatter, "invalid type: {}, expected {}", self.unexp, self.exp) } } Error::custom(InvalidType { unexp: unexp, exp: exp }) } /// Raised when a `Deserialize` receives a value of the right type but that /// is wrong for some other reason. /// /// The `unexp` argument provides information about what value was received. /// This is the value that was present in the input file or other source /// data of the Deserializer. /// /// The `exp` argument provides information about what value was being /// expected. This is the type that is written in the program. /// /// For example if we try to deserialize a String out of some binary data /// that is not valid UTF-8, the unexpected value is the bytes and the /// expected value is a string. fn invalid_value(unexp: Unexpected, exp: &Expected) -> Self { struct InvalidValue<'a> { unexp: Unexpected<'a>, exp: &'a Expected, } impl<'a> Display for InvalidValue<'a> { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { write!(formatter, "invalid value: {}, expected {}", self.unexp, self.exp) } } Error::custom(InvalidValue { unexp: unexp, exp: exp }) } /// Raised when deserializing a sequence or map and the input data contains /// too many or too few elements. /// /// The `len` argument is the number of elements encountered. The sequence /// or map may have expected more arguments or fewer arguments. /// /// The `exp` argument provides information about what data was being /// expected. For example `exp` might say that a tuple of size 6 was /// expected. fn invalid_length(len: usize, exp: &Expected) -> Self { struct InvalidLength<'a> { len: usize, exp: &'a Expected, } impl<'a> Display for InvalidLength<'a> { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { write!(formatter, "invalid length {}, expected {}", self.len, self.exp) } } Error::custom(InvalidLength { len: len, exp: exp }) } /// Raised when a `Deserialize` enum type received a variant with an /// unrecognized name. fn unknown_variant(variant: &str, expected: &'static [&'static str]) -> Self { struct UnknownVariant<'a> { variant: &'a str, expected: &'static [&'static str], } impl<'a> Display for UnknownVariant<'a> { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { if self.expected.is_empty() { write!(formatter, "unknown variant `{}`, there are no variants", self.variant) } else { write!(formatter, "unknown variant `{}`, expected {}", self.variant, OneOf { names: self.expected }) } } } Error::custom(UnknownVariant { variant: variant, expected: expected }) } /// Raised when a `Deserialize` struct type received a field with an /// unrecognized name. fn unknown_field(field: &str, expected: &'static [&'static str]) -> Self { struct UnknownField<'a> { field: &'a str, expected: &'static [&'static str], } impl<'a> Display for UnknownField<'a> { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { if self.expected.is_empty() { write!(formatter, "unknown field `{}`, there are no fields", self.field) } else { write!(formatter, "unknown field `{}`, expected {}", self.field, OneOf { names: self.expected }) } } } Error::custom(UnknownField { field: field, expected: expected }) } /// Raised when a `Deserialize` struct type expected to receive a required /// field with a particular name but that field was not present in the /// input. fn missing_field(field: &'static str) -> Self { struct MissingField { field: &'static str, } impl Display for MissingField { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { write!(formatter, "missing field `{}`", self.field) } } Error::custom(MissingField { field: field }) } /// Raised when a `Deserialize` struct type received more than one of the /// same field. fn duplicate_field(field: &'static str) -> Self { struct DuplicateField { field: &'static str, } impl Display for DuplicateField { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { write!(formatter, "duplicate field `{}`", self.field) } } Error::custom(DuplicateField { field: field }) } } /// `Unexpected` represents an unexpected invocation of any one of the `Visitor` /// trait methods. /// /// This is used as an argument to the `invalid_type`, `invalid_value`, and /// `invalid_length` methods of the `Error` trait to build error messages. /// /// ```rust /// # use serde::de::{Error, Unexpected, Visitor}; /// # use std::fmt; /// # struct Example; /// # impl Visitor for Example { /// # type Value = (); /// fn visit_bool<E>(self, v: bool) -> Result<Self::Value, E> /// where E: Error /// { /// Err(Error::invalid_type(Unexpected::Bool(v), &self)) /// } /// # fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result { /// # write!(formatter, "definitely not a boolean") /// # } /// # } /// ``` #[derive(Clone, PartialEq, Debug)] pub enum Unexpected<'a> { /// The input contained a boolean value that was not expected. Bool(bool), /// The input contained an unsigned integer `usize`, `u8`, `u16`, `u32` or /// `u64` that was not expected. Unsigned(u64), /// The input contained a signed integer `isize`, `i8`, `i16`, `i32` or /// `i64` that was not expected. Signed(i64), /// The input contained a floating point `f32` or `f64` that was not /// expected. Float(f64), /// The input contained a `char` that was not expected. Char(char), /// The input contained a `&str` or `String` that was not expected. Str(&'a str), /// The input contained a `&[u8]` or `Vec<u8>` that was not expected. Bytes(&'a [u8]), /// The input contained a unit `()` that was not expected. Unit, /// The input contained an `Option<T>` that was not expected. Option, /// The input contained a newtype struct that was not expected. NewtypeStruct, /// The input contained a sequence that was not expected. Seq, /// The input contained a map that was not expected. Map, /// The input contained an enum that was not expected. Enum, /// The input contained a unit variant that was not expected. UnitVariant, /// The input contained a newtype variant that was not expected. NewtypeVariant, /// The input contained a tuple variant that was not expected. TupleVariant, /// The input contained a struct variant that was not expected. StructVariant, /// A message stating what uncategorized thing the input contained that was /// not expected. /// /// The message should be a noun or noun phrase, not capitalized and without /// a period. An example message is "unoriginal superhero". Other(&'a str), } impl<'a> fmt::Display for Unexpected<'a> { fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> { use self::Unexpected::*; match *self { Bool(b) => write!(formatter, "boolean `{}`", b), Unsigned(i) => write!(formatter, "integer `{}`", i), Signed(i) => write!(formatter, "integer `{}`", i), Float(f) => write!(formatter, "floating point `{}`", f), Char(c) => write!(formatter, "character `{}`", c), Str(s) => write!(formatter, "string {:?}", s), Bytes(_) => write!(formatter, "byte array"), Unit => write!(formatter, "unit value"), Option => write!(formatter, "Option value"), NewtypeStruct => write!(formatter, "newtype struct"), Seq => write!(formatter, "sequence"), Map => write!(formatter, "map"), Enum => write!(formatter, "enum"), UnitVariant => write!(formatter, "unit variant"), NewtypeVariant => write!(formatter, "newtype variant"), TupleVariant => write!(formatter, "tuple variant"), StructVariant => write!(formatter, "struct variant"), Other(other) => formatter.write_str(other), } } } /// `Expected` represents an explanation of what data a `Visitor` was expecting /// to receive. /// /// This is used as an argument to the `invalid_type`, `invalid_value`, and /// `invalid_length` methods of the `Error` trait to build error messages. The /// message should complete the sentence "This Visitor expects to receive ...", /// for example the message could be "an integer between 0 and 64". The message /// should not be capitalized and should not end with a period. /// /// Within the context of a `Visitor` implementation, the `Visitor` itself /// (`&self`) is an implementation of this trait. /// /// ```rust /// # use serde::de::{Error, Unexpected, Visitor}; /// # use std::fmt; /// # struct Example; /// # impl Visitor for Example { /// # type Value = (); /// fn visit_bool<E>(self, v: bool) -> Result<Self::Value, E> /// where E: Error /// { /// Err(Error::invalid_type(Unexpected::Bool(v), &self)) /// } /// # fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result { /// # write!(formatter, "definitely not a boolean") /// # } /// # } /// ``` /// /// Outside of a `Visitor`, `&"..."` can be used. /// /// ```rust /// # use serde::de::{Error, Unexpected}; /// # fn example<E: Error>() -> Result<(), E> { /// # let v = true; /// return Err(Error::invalid_type(Unexpected::Bool(v), &"a negative integer")); /// # } /// ``` pub trait Expected { /// Format an explanation of what data was being expected. Same signature as /// the `Display` and `Debug` traits. fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result; } impl<T> Expected for T where T: Visitor { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { self.expecting(formatter) } } impl<'a> Expected for &'a str { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { formatter.write_str(self) } } impl<'a> Display for Expected + 'a { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { Expected::fmt(self, formatter) } } /////////////////////////////////////////////////////////////////////////////// /// `Deserialize` represents a type that can be deserialized. pub trait Deserialize: Sized { /// Deserialize this value given this `Deserializer`. fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where D: Deserializer; } /// `DeserializeSeed` is the stateful form of the `Deserialize` trait. If you /// ever find yourself looking for a way to pass data into a `Deserialize` impl, /// this trait is the way to do it. /// /// As one example of stateful deserialization consider deserializing a JSON /// array into an existing buffer. Using the `Deserialize` trait we could /// deserialize a JSON array into a `Vec<T>` but it would be a freshly allocated /// `Vec<T>`; there is no way for `Deserialize` to reuse a previously allocated /// buffer. Using `DeserializeSeed` instead makes this possible as in the /// example code below. /// /// The canonical API for stateless deserialization looks like this: /// /// ```rust /// # use serde::Deserialize; /// # enum Error {} /// fn func<T: Deserialize>() -> Result<T, Error> /// # { unimplemented!() } /// ``` /// /// Adjusting an API like this to support stateful deserialization is a matter /// of accepting a seed as input: /// /// ```rust /// # use serde::de::DeserializeSeed; /// # enum Error {} /// fn func_seed<T: DeserializeSeed>(seed: T) -> Result<T::Value, Error> /// # { unimplemented!() } /// ``` /// /// In practice the majority of deserialization is stateless. An API expecting a /// seed can be appeased by passing `std::marker::PhantomData` as a seed in the /// case of stateless deserialization. /// /// # Example /// /// Suppose we have JSON that looks like `[[1, 2], [3, 4, 5], [6]]` and we need /// to deserialize it into a flat representation like `vec![1, 2, 3, 4, 5, 6]`. /// Allocating a brand new `Vec<T>` for each subarray would be slow. Instead we /// would like to allocate a single `Vec<T>` and then deserialize each subarray /// into it. This requires stateful deserialization using the `DeserializeSeed` /// trait. /// /// ```rust /// # use serde::de::{Deserialize, DeserializeSeed, Deserializer, Visitor, SeqVisitor}; /// # use std::fmt; /// # use std::marker::PhantomData; /// # /// // A DeserializeSeed implementation that uses stateful deserialization to /// // append array elements onto the end of an existing vector. The preexisting /// // state ("seed") in this case is the Vec<T>. The `deserialize` method of /// // `ExtendVec` will be traversing the inner arrays of the JSON input and /// // appending each integer into the existing Vec. /// struct ExtendVec<'a, T: 'a>(&'a mut Vec<T>); /// /// impl<'a, T> DeserializeSeed for ExtendVec<'a, T> /// where T: Deserialize /// { /// // The return type of the `deserialize` method. This implementation /// // appends onto an existing vector but does not create any new data /// // structure, so the return type is (). /// type Value = (); /// /// fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error> /// where D: Deserializer /// { /// // Visitor implementation that will walk an inner array of the JSON /// // input. /// struct ExtendVecVisitor<'a, T: 'a>(&'a mut Vec<T>); /// /// impl<'a, T> Visitor for ExtendVecVisitor<'a, T> /// where T: Deserialize /// { /// type Value = (); /// /// fn visit_seq<V>(self, mut visitor: V) -> Result<(), V::Error> /// where V: SeqVisitor /// { /// // Visit each element in the inner array and push it onto /// // the existing vector. /// while let Some(elem) = visitor.visit()? { /// self.0.push(elem); /// } /// Ok(()) /// } /// # /// # fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result { /// # write!(formatter, "an array of integers") /// # } /// } /// /// deserializer.deserialize_seq(ExtendVecVisitor(self.0)) /// } /// } /// /// // Visitor implementation that will walk the outer array of the JSON input. /// struct FlattenedVecVisitor<T>(PhantomData<T>); /// /// impl<T> Visitor for FlattenedVecVisitor<T> /// where T: Deserialize /// { /// // This Visitor constructs a single Vec<T> to hold the flattened /// // contents of the inner arrays. /// type Value = Vec<T>; /// /// fn visit_seq<V>(self, mut visitor: V) -> Result<Vec<T>, V::Error> /// where V: SeqVisitor /// { /// // Create a single Vec to hold the flattened contents. /// let mut vec = Vec::new(); /// /// // Each iteration through this loop is one inner array. /// while let Some(()) = visitor.visit_seed(ExtendVec(&mut vec))? { /// // Nothing to do; inner array has been appended into `vec`. /// } /// /// // Return the finished vec. /// Ok(vec) /// } /// # /// # fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result { /// # write!(formatter, "an array of arrays") /// # } /// } /// /// # fn example<D: Deserializer>(deserializer: D) -> Result<(), D::Error> { /// let visitor = FlattenedVecVisitor(PhantomData); /// let flattened: Vec<u64> = deserializer.deserialize_seq(visitor)?; /// # Ok(()) } /// ``` pub trait DeserializeSeed: Sized { /// The type produced by using this seed. type Value; /// Equivalent to the more common `Deserialize::deserialize` method, except /// with some initial piece of data (the seed) passed in. fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error> where D: Deserializer; } impl<T> DeserializeSeed for PhantomData<T> where T: Deserialize { type Value = T; #[inline] fn deserialize<D>(self, deserializer: D) -> Result<T, D::Error> where D: Deserializer { T::deserialize(deserializer) } } /////////////////////////////////////////////////////////////////////////////// /// `Deserializer` is a trait that can deserialize values by threading a `Visitor` trait through a /// value. It supports two entry point styles which enables different kinds of deserialization. /// /// 1) The `deserialize` method. File formats like JSON embed the type of its construct in its file /// format. This allows the `Deserializer` to deserialize into a generic type like /// `json::Value`, which can represent all JSON types. /// /// 2) The `deserialize_*` methods. File formats like bincode do not embed in its format how to /// decode its values. It relies instead on the `Deserialize` type to hint to the `Deserializer` /// with the `deserialize_*` methods how it should parse the next value. One downside though to /// only supporting the `deserialize_*` types is that it does not allow for deserializing into a /// generic `json::Value`-esque type. pub trait Deserializer: Sized { /// The error type that can be returned if some error occurs during deserialization. type Error: Error; /// This method walks a visitor through a value as it is being deserialized. fn deserialize<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a `bool` value. fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `usize` value. /// A reasonable default is to forward to `deserialize_u64`. fn deserialize_usize<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `u8` value. /// A reasonable default is to forward to `deserialize_u64`. fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `u16` value. /// A reasonable default is to forward to `deserialize_u64`. fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `u32` value. /// A reasonable default is to forward to `deserialize_u64`. fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `u64` value. fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `isize` value. /// A reasonable default is to forward to `deserialize_i64`. fn deserialize_isize<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `i8` value. /// A reasonable default is to forward to `deserialize_i64`. fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `i16` value. /// A reasonable default is to forward to `deserialize_i64`. fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `i32` value. /// A reasonable default is to forward to `deserialize_i64`. fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `i64` value. fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a `f32` value. /// A reasonable default is to forward to `deserialize_f64`. fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a `f64` value. fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a `char` value. fn deserialize_char<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a `&str` value. fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a `String` value. fn deserialize_string<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `unit` value. fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an `Option` value. This allows /// deserializers that encode an optional value as a nullable value to convert the null value /// into a `None`, and a regular value as `Some(value)`. fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a sequence value. This allows /// deserializers to parse sequences that aren't tagged as sequences. fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a fixed size array. This allows /// deserializers to parse arrays that aren't tagged as arrays. fn deserialize_seq_fixed_size<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a `&[u8]`. This allows /// deserializers that provide a custom byte vector serialization to properly deserialize the /// type. fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a `Vec<u8>`. This allows /// deserializers that provide a custom byte vector serialization to properly deserialize the /// type and prevent needless intermediate allocations that would occur when going through /// `&[u8]`. fn deserialize_byte_buf<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a map of values. This allows /// deserializers to parse sequences that aren't tagged as maps. fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a unit struct. This allows /// deserializers to a unit struct that aren't tagged as a unit struct. fn deserialize_unit_struct<V>(self, name: &'static str, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a newtype struct. This allows /// deserializers to a newtype struct that aren't tagged as a newtype struct. /// A reasonable default is to simply deserialize the expected value directly. fn deserialize_newtype_struct<V>(self, name: &'static str, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a tuple struct. This allows /// deserializers to parse sequences that aren't tagged as sequences. fn deserialize_tuple_struct<V>(self, name: &'static str, len: usize, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a struct. This allows /// deserializers to parse sequences that aren't tagged as maps. fn deserialize_struct<V>(self, name: &'static str, fields: &'static [&'static str], visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting some sort of struct field /// name. This allows deserializers to choose between &str, usize, or &[u8] to properly /// deserialize a struct field. fn deserialize_struct_field<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting a tuple value. This allows /// deserializers that provide a custom tuple serialization to properly deserialize the type. fn deserialize_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type is expecting an enum value. This allows /// deserializers that provide a custom enumeration serialization to properly deserialize the /// type. fn deserialize_enum<V>(self, name: &'static str, variants: &'static [&'static str], visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// This method hints that the `Deserialize` type needs to deserialize a value whose type /// doesn't matter because it is ignored. fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; } /////////////////////////////////////////////////////////////////////////////// /// This trait represents a visitor that walks through a deserializer. /// /// ```rust /// # use serde::de::{Error, Unexpected, Visitor}; /// # use std::fmt; /// /// A visitor that deserializes a long string - a string containing at least /// /// some minimum number of bytes. /// struct LongString { /// min: usize, /// } /// /// impl Visitor for LongString { /// type Value = String; /// /// fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result { /// write!(formatter, "a string containing at least {} bytes", self.min) /// } /// /// fn visit_str<E>(self, s: &str) -> Result<Self::Value, E> /// where E: Error /// { /// if s.len() >= self.min { /// Ok(s.to_owned()) /// } else { /// Err(Error::invalid_value(Unexpected::Str(s), &self)) /// } /// } /// } /// ``` pub trait Visitor: Sized { /// The value produced by this visitor. type Value; /// Format a message stating what data this Visitor expects to receive. /// /// This is used in error messages. The message should complete the sentence /// "This Visitor expects to receive ...", for example the message could be /// "an integer between 0 and 64". The message should not be capitalized and /// should not end with a period. /// /// ```rust /// # use std::fmt; /// # struct S { max: usize } /// # impl serde::de::Visitor for S { /// # type Value = (); /// fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result { /// write!(formatter, "an integer between 0 and {}", self.max) /// } /// # } /// ``` fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result; /// `visit_bool` deserializes a `bool` into a `Value`. fn visit_bool<E>(self, v: bool) -> Result<Self::Value, E> where E: Error, { Err(Error::invalid_type(Unexpected::Bool(v), &self)) } /// `visit_isize` deserializes a `isize` into a `Value`. fn visit_isize<E>(self, v: isize) -> Result<Self::Value, E> where E: Error, { self.visit_i64(v as i64) } /// `visit_i8` deserializes a `i8` into a `Value`. fn visit_i8<E>(self, v: i8) -> Result<Self::Value, E> where E: Error, { self.visit_i64(v as i64) } /// `visit_i16` deserializes a `i16` into a `Value`. fn visit_i16<E>(self, v: i16) -> Result<Self::Value, E> where E: Error, { self.visit_i64(v as i64) } /// `visit_i32` deserializes a `i32` into a `Value`. fn visit_i32<E>(self, v: i32) -> Result<Self::Value, E> where E: Error, { self.visit_i64(v as i64) } /// `visit_i64` deserializes a `i64` into a `Value`. fn visit_i64<E>(self, v: i64) -> Result<Self::Value, E> where E: Error, { Err(Error::invalid_type(Unexpected::Signed(v), &self)) } /// `visit_usize` deserializes a `usize` into a `Value`. fn visit_usize<E>(self, v: usize) -> Result<Self::Value, E> where E: Error, { self.visit_u64(v as u64) } /// `visit_u8` deserializes a `u8` into a `Value`. fn visit_u8<E>(self, v: u8) -> Result<Self::Value, E> where E: Error, { self.visit_u64(v as u64) } /// `visit_u16` deserializes a `u16` into a `Value`. fn visit_u16<E>(self, v: u16) -> Result<Self::Value, E> where E: Error, { self.visit_u64(v as u64) } /// `visit_u32` deserializes a `u32` into a `Value`. fn visit_u32<E>(self, v: u32) -> Result<Self::Value, E> where E: Error, { self.visit_u64(v as u64) } /// `visit_u64` deserializes a `u64` into a `Value`. fn visit_u64<E>(self, v: u64) -> Result<Self::Value, E> where E: Error, { Err(Error::invalid_type(Unexpected::Unsigned(v), &self)) } /// `visit_f32` deserializes a `f32` into a `Value`. fn visit_f32<E>(self, v: f32) -> Result<Self::Value, E> where E: Error, { self.visit_f64(v as f64) } /// `visit_f64` deserializes a `f64` into a `Value`. fn visit_f64<E>(self, v: f64) -> Result<Self::Value, E> where E: Error, { Err(Error::invalid_type(Unexpected::Float(v), &self)) } /// `visit_char` deserializes a `char` into a `Value`. #[inline] fn visit_char<E>(self, v: char) -> Result<Self::Value, E> where E: Error, { self.visit_str(::utils::encode_utf8(v).as_str()) } /// `visit_str` deserializes a `&str` into a `Value`. fn visit_str<E>(self, v: &str) -> Result<Self::Value, E> where E: Error, { Err(Error::invalid_type(Unexpected::Str(v), &self)) } /// `visit_string` deserializes a `String` into a `Value`. This allows a deserializer to avoid /// a copy if it is deserializing a string from a `String` type. By default it passes a `&str` /// to the `visit_str` method. #[inline] #[cfg(any(feature = "std", feature = "collections"))] fn visit_string<E>(self, v: String) -> Result<Self::Value, E> where E: Error, { self.visit_str(&v) } /// `visit_unit` deserializes a `()` into a `Value`. fn visit_unit<E>(self) -> Result<Self::Value, E> where E: Error, { Err(Error::invalid_type(Unexpected::Unit, &self)) } /// `visit_none` deserializes a none value into a `Value`. fn visit_none<E>(self) -> Result<Self::Value, E> where E: Error, { Err(Error::invalid_type(Unexpected::Option, &self)) } /// `visit_some` deserializes a value into a `Value`. fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error> where D: Deserializer, { let _ = deserializer; Err(Error::invalid_type(Unexpected::Option, &self)) } /// `visit_newtype_struct` deserializes a value into a `Value`. fn visit_newtype_struct<D>(self, deserializer: D) -> Result<Self::Value, D::Error> where D: Deserializer, { let _ = deserializer; Err(Error::invalid_type(Unexpected::NewtypeStruct, &self)) } /// `visit_seq` deserializes a `SeqVisitor` into a `Value`. fn visit_seq<V>(self, visitor: V) -> Result<Self::Value, V::Error> where V: SeqVisitor, { let _ = visitor; Err(Error::invalid_type(Unexpected::Seq, &self)) } /// `visit_map` deserializes a `MapVisitor` into a `Value`. fn visit_map<V>(self, visitor: V) -> Result<Self::Value, V::Error> where V: MapVisitor, { let _ = visitor; Err(Error::invalid_type(Unexpected::Map, &self)) } /// `visit_enum` deserializes a `EnumVisitor` into a `Value`. fn visit_enum<V>(self, visitor: V) -> Result<Self::Value, V::Error> where V: EnumVisitor, { let _ = visitor; Err(Error::invalid_type(Unexpected::Enum, &self)) } /// `visit_bytes` deserializes a `&[u8]` into a `Value`. fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E> where E: Error, { let _ = v; Err(Error::invalid_type(Unexpected::Bytes(v), &self)) } /// `visit_byte_buf` deserializes a `Vec<u8>` into a `Value`. #[cfg(any(feature = "std", feature = "collections"))] fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E> where E: Error, { self.visit_bytes(&v) } } /////////////////////////////////////////////////////////////////////////////// /// `SeqVisitor` visits each item in a sequence. /// /// This is a trait that a `Deserializer` passes to a `Visitor` implementation, which deserializes /// each item in a sequence. pub trait SeqVisitor { /// The error type that can be returned if some error occurs during deserialization. type Error: Error; /// This returns `Ok(Some(value))` for the next value in the sequence, or /// `Ok(None)` if there are no more remaining items. /// /// `Deserialize` implementations should typically use `SeqVisitor::visit` /// instead. fn visit_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error> where T: DeserializeSeed; /// This returns `Ok(Some(value))` for the next value in the sequence, or /// `Ok(None)` if there are no more remaining items. /// /// This method exists as a convenience for `Deserialize` implementations. /// `SeqVisitor` implementations should not need to override the default /// behavior. #[inline] fn visit<T>(&mut self) -> Result<Option<T>, Self::Error> where T: Deserialize { self.visit_seed(PhantomData) } /// Return the lower and upper bound of items remaining in the sequence. #[inline] fn size_hint(&self) -> (usize, Option<usize>) { (0, None) } } impl<'a, V> SeqVisitor for &'a mut V where V: SeqVisitor { type Error = V::Error; #[inline] fn visit_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, V::Error> where T: DeserializeSeed { (**self).visit_seed(seed) } #[inline] fn visit<T>(&mut self) -> Result<Option<T>, V::Error> where T: Deserialize { (**self).visit() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { (**self).size_hint() } } /////////////////////////////////////////////////////////////////////////////// /// `MapVisitor` visits each item in a sequence. /// /// This is a trait that a `Deserializer` passes to a `Visitor` implementation. pub trait MapVisitor { /// The error type that can be returned if some error occurs during deserialization. type Error: Error; /// This returns `Ok(Some(key))` for the next key in the map, or `Ok(None)` /// if there are no more remaining entries. /// /// `Deserialize` implementations should typically use /// `MapVisitor::visit_key` or `MapVisitor::visit` instead. fn visit_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error> where K: DeserializeSeed; /// This returns a `Ok(value)` for the next value in the map. /// /// `Deserialize` implementations should typically use /// `MapVisitor::visit_value` instead. fn visit_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error> where V: DeserializeSeed; /// This returns `Ok(Some((key, value)))` for the next (key-value) pair in /// the map, or `Ok(None)` if there are no more remaining items. /// /// `MapVisitor` implementations should override the default behavior if a /// more efficient implementation is possible. /// /// `Deserialize` implementations should typically use `MapVisitor::visit` /// instead. #[inline] fn visit_seed<K, V>(&mut self, kseed: K, vseed: V) -> Result<Option<(K::Value, V::Value)>, Self::Error> where K: DeserializeSeed, V: DeserializeSeed { match try!(self.visit_key_seed(kseed)) { Some(key) => { let value = try!(self.visit_value_seed(vseed)); Ok(Some((key, value))) } None => Ok(None) } } /// This returns `Ok(Some(key))` for the next key in the map, or `Ok(None)` /// if there are no more remaining entries. /// /// This method exists as a convenience for `Deserialize` implementations. /// `MapVisitor` implementations should not need to override the default /// behavior. #[inline] fn visit_key<K>(&mut self) -> Result<Option<K>, Self::Error> where K: Deserialize { self.visit_key_seed(PhantomData) } /// This returns a `Ok(value)` for the next value in the map. /// /// This method exists as a convenience for `Deserialize` implementations. /// `MapVisitor` implementations should not need to override the default /// behavior. #[inline] fn visit_value<V>(&mut self) -> Result<V, Self::Error> where V: Deserialize { self.visit_value_seed(PhantomData) } /// This returns `Ok(Some((key, value)))` for the next (key-value) pair in /// the map, or `Ok(None)` if there are no more remaining items. /// /// This method exists as a convenience for `Deserialize` implementations. /// `MapVisitor` implementations should not need to override the default /// behavior. #[inline] fn visit<K, V>(&mut self) -> Result<Option<(K, V)>, Self::Error> where K: Deserialize, V: Deserialize, { self.visit_seed(PhantomData, PhantomData) } /// Return the lower and upper bound of items remaining in the sequence. #[inline] fn size_hint(&self) -> (usize, Option<usize>) { (0, None) } } impl<'a, V_> MapVisitor for &'a mut V_ where V_: MapVisitor { type Error = V_::Error; #[inline] fn visit_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error> where K: DeserializeSeed { (**self).visit_key_seed(seed) } #[inline] fn visit_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error> where V: DeserializeSeed { (**self).visit_value_seed(seed) } #[inline] fn visit_seed<K, V>(&mut self, kseed: K, vseed: V) -> Result<Option<(K::Value, V::Value)>, Self::Error> where K: DeserializeSeed, V: DeserializeSeed { (**self).visit_seed(kseed, vseed) } #[inline] fn visit<K, V>(&mut self) -> Result<Option<(K, V)>, V_::Error> where K: Deserialize, V: Deserialize, { (**self).visit() } #[inline] fn visit_key<K>(&mut self) -> Result<Option<K>, V_::Error> where K: Deserialize { (**self).visit_key() } #[inline] fn visit_value<V>(&mut self) -> Result<V, V_::Error> where V: Deserialize { (**self).visit_value() } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { (**self).size_hint() } } /////////////////////////////////////////////////////////////////////////////// /// `EnumVisitor` is a visitor that is created by the `Deserializer` and passed /// to the `Deserialize` in order to identify which variant of an enum to /// deserialize. pub trait EnumVisitor: Sized { /// The error type that can be returned if some error occurs during deserialization. type Error: Error; /// The `Visitor` that will be used to deserialize the content of the enum /// variant. type Variant: VariantVisitor<Error=Self::Error>; /// `visit_variant` is called to identify which variant to deserialize. /// /// `Deserialize` implementations should typically use /// `EnumVisitor::visit_variant` instead. fn visit_variant_seed<V>(self, seed: V) -> Result<(V::Value, Self::Variant), Self::Error> where V: DeserializeSeed; /// `visit_variant` is called to identify which variant to deserialize. /// /// This method exists as a convenience for `Deserialize` implementations. /// `EnumVisitor` implementations should not need to override the default /// behavior. #[inline] fn visit_variant<V>(self) -> Result<(V, Self::Variant), Self::Error> where V: Deserialize { self.visit_variant_seed(PhantomData) } } /// `VariantVisitor` is a visitor that is created by the `Deserializer` and /// passed to the `Deserialize` to deserialize the content of a particular enum /// variant. pub trait VariantVisitor: Sized { /// The error type that can be returned if some error occurs during deserialization. type Error: Error; /// `visit_unit` is called when deserializing a variant with no values. fn visit_unit(self) -> Result<(), Self::Error>; /// `visit_newtype` is called when deserializing a variant with a single value. /// A good default is often to use the `visit_tuple` method to deserialize a `(value,)`. /// /// `Deserialize` implementations should typically use /// `VariantVisitor::visit_newtype` instead. fn visit_newtype_seed<T>(self, seed: T) -> Result<T::Value, Self::Error> where T: DeserializeSeed; /// `visit_newtype` is called when deserializing a variant with a single value. /// A good default is often to use the `visit_tuple` method to deserialize a `(value,)`. /// /// This method exists as a convenience for `Deserialize` implementations. /// `VariantVisitor` implementations should not need to override the default /// behavior. #[inline] fn visit_newtype<T>(self) -> Result<T, Self::Error> where T: Deserialize { self.visit_newtype_seed(PhantomData) } /// `visit_tuple` is called when deserializing a tuple-like variant. /// If no tuple variants are expected, yield a /// `Err(serde::de::Error::invalid_type(serde::de::Type::TupleVariant))` fn visit_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; /// `visit_struct` is called when deserializing a struct-like variant. /// If no struct variants are expected, yield a /// `Err(serde::de::Error::invalid_type(serde::de::Type::StructVariant))` fn visit_struct<V>(self, fields: &'static [&'static str], visitor: V) -> Result<V::Value, Self::Error> where V: Visitor; } /////////////////////////////////////////////////////////////////////////////// /// Used in error messages. /// /// - expected `a` /// - expected `a` or `b` /// - expected one of `a`, `b`, `c` struct OneOf { names: &'static [&'static str], } impl Display for OneOf { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { match self.names.len() { 0 => panic!(), // special case elsewhere 1 => write!(formatter, "`{}`", self.names[0]), 2 => write!(formatter, "`{}` or `{}`", self.names[0], self.names[1]), _ => { try!(write!(formatter, "one of ")); for (i, alt) in self.names.iter().enumerate() { if i > 0 { try!(write!(formatter, ", ")); } try!(write!(formatter, "`{}`", alt)); } Ok(()) } } } }