serde_with/
key_value_map.rs

1use crate::{
2    content::{
3        de::{Content as DeContent, ContentDeserializer},
4        ser::{Content as SerContent, ContentSerializer},
5    },
6    prelude::*,
7};
8
9/// Convert `Vec` elements into key-value map entries
10///
11/// This maps a single struct/tuple/etc. to a map entry.
12/// The map key is converted to a struct field.
13/// The other values will be mapped to the map value.
14///
15/// The conversion supports structs, tuple structs, tuples, maps, and sequences.
16/// Structs need a field that is named `$key$` to be used as the map key.
17/// This can be done with the `#[serde(rename = "$key$")]` attribute.
18/// Maps similarly need a map-key that is named `$key$`.
19/// For tuples, tuple structs, and sequences the first element is used as the map key.
20///
21/// # Examples
22///
23/// ## Struct with String key in JSON
24///
25/// ```rust
26/// # #[cfg(feature = "macros")] {
27/// # use serde::{Deserialize, Serialize};
28/// use serde_with::{serde_as, KeyValueMap};
29///
30/// # #[derive(Debug, Clone, PartialEq, Eq)]
31/// #[derive(Serialize, Deserialize)]
32/// struct SimpleStruct {
33///     b: bool,
34///     // The field named `$key$` will become the map key
35///     #[serde(rename = "$key$")]
36///     id: String,
37///     i: i32,
38/// }
39///
40/// #[serde_as]
41/// # #[derive(Debug, Clone, PartialEq, Eq)]
42/// #[derive(Serialize, Deserialize)]
43/// struct KVMap(
44///     #[serde_as(as = "KeyValueMap<_>")]
45///     Vec<SimpleStruct>,
46/// );
47///
48/// // ---
49///
50/// // This will serialize this list of values
51/// let values = KVMap(vec![
52///     SimpleStruct {
53///         b: false,
54///         id: "id-0000".to_string(),
55///         i: 123,
56///     },
57///     SimpleStruct {
58///         b: true,
59///         id: "id-0001".to_string(),
60///         i: 555,
61///     },
62///     SimpleStruct {
63///         b: false,
64///         id: "id-0002".to_string(),
65///         i: 987,
66///     },
67/// ]);
68///
69/// // into this JSON map
70/// let expected =
71/// r#"{
72///   "id-0000": {
73///     "b": false,
74///     "i": 123
75///   },
76///   "id-0001": {
77///     "b": true,
78///     "i": 555
79///   },
80///   "id-0002": {
81///     "b": false,
82///     "i": 987
83///   }
84/// }"#;
85///
86/// // Both serialization and deserialization work flawlessly.
87/// let serialized = serde_json::to_string_pretty(&values).unwrap();
88/// assert_eq!(expected, serialized);
89/// let deserialized: KVMap = serde_json::from_str(&serialized).unwrap();
90/// assert_eq!(values, deserialized);
91/// # }
92/// ```
93///
94/// ## Tuple struct with complex key in YAML
95///
96/// ```rust
97/// # #[cfg(feature = "macros")] {
98/// # use serde::{Deserialize, Serialize};
99/// use serde_with::{serde_as, KeyValueMap};
100/// use std::net::IpAddr;
101/// # use std::str::FromStr;
102///
103/// # #[derive(Debug, Clone, PartialEq, Eq)]
104/// #[derive(Serialize, Deserialize)]
105/// struct TupleStruct (
106///     // The first element in a tuple struct, tuple, or sequence becomes the map key
107///     (IpAddr, u8),
108///     bool,
109/// );
110///
111/// #[serde_as]
112/// # #[derive(Debug, Clone, PartialEq, Eq)]
113/// #[derive(Serialize, Deserialize)]
114/// struct KVMap(
115///     #[serde_as(as = "KeyValueMap<_>")]
116///     Vec<TupleStruct>,
117/// );
118///
119/// // ---
120///
121/// // This will serialize this list of values
122/// let values = KVMap(vec![
123///     TupleStruct(
124///         (IpAddr::from_str("127.0.0.1").unwrap(), 8),
125///         true
126///     ),
127///     TupleStruct(
128///         (IpAddr::from_str("::1").unwrap(), 128),
129///         true
130///     ),
131///     TupleStruct(
132///         (IpAddr::from_str("198.51.100.0").unwrap(), 24),
133///         true
134///     ),
135/// ]);
136///
137/// // into this YAML
138/// let expected =
139/// r#"? - 127.0.0.1
140///   - 8
141/// : - true
142/// ? - ::1
143///   - 128
144/// : - true
145/// ? - 198.51.100.0
146///   - 24
147/// : - true
148/// "#;
149///
150/// // Both serialization and deserialization work flawlessly.
151/// let serialized = yaml_serde::to_string(&values).unwrap();
152/// assert_eq!(expected, serialized);
153/// let deserialized: KVMap = yaml_serde::from_str(&serialized).unwrap();
154/// assert_eq!(values, deserialized);
155/// # }
156/// ```
157pub struct KeyValueMap<T>(PhantomData<T>);
158
159impl<T, TAs> SerializeAs<Vec<T>> for KeyValueMap<TAs>
160where
161    TAs: SerializeAs<T>,
162{
163    fn serialize_as<S>(source: &Vec<T>, serializer: S) -> Result<S::Ok, S::Error>
164    where
165        S: Serializer,
166    {
167        <Vec<TAs>>::serialize_as(source, SeqAsMapSerializer(serializer))
168    }
169}
170
171impl<'de, T, TAs> DeserializeAs<'de, Vec<T>> for KeyValueMap<TAs>
172where
173    TAs: DeserializeAs<'de, T>,
174{
175    fn deserialize_as<D>(deserializer: D) -> Result<Vec<T>, D::Error>
176    where
177        D: Deserializer<'de>,
178    {
179        struct KeyValueMapVisitor<T, TAs> {
180            is_human_readable: bool,
181            phantom: PhantomData<(T, TAs)>,
182        }
183
184        impl<'de, T, TAs> Visitor<'de> for KeyValueMapVisitor<T, TAs>
185        where
186            TAs: DeserializeAs<'de, T>,
187        {
188            type Value = Vec<T>;
189
190            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
191                formatter.write_str("a map")
192            }
193
194            fn visit_map<A: MapAccess<'de>>(self, map: A) -> Result<Self::Value, A::Error> {
195                <Vec<TAs>>::deserialize_as(SeqDeserializer {
196                    delegate: map,
197                    is_human_readable: self.is_human_readable,
198                })
199            }
200        }
201
202        let is_human_readable = deserializer.is_human_readable();
203        deserializer.deserialize_map(KeyValueMapVisitor::<T, TAs> {
204            is_human_readable,
205            phantom: PhantomData,
206        })
207    }
208}
209
210// TODO Replace this with a const generic string once adt_const_params is stable.
211// This will allow something like this.
212// The `"id"` part is the field name, which gets converted to/from the map key.
213// #[serde_as(as = r#"KeyValueMap<"id", _>"#)]
214// Vec<SimpleStruct>,
215static MAP_KEY_IDENTIFIER: &str = "$key$";
216
217/// Convert a sequence to a map during serialization.
218///
219/// Only `serialize_seq` is implemented and forwarded to `serialize_map` on the inner `Serializer`.
220/// The elements are serialized with [`SerializeSeqElement`].
221struct SeqAsMapSerializer<S>(S);
222
223impl<S> Serializer for SeqAsMapSerializer<S>
224where
225    S: Serializer,
226{
227    type Ok = S::Ok;
228    type Error = S::Error;
229
230    type SerializeSeq = SerializeSeqElement<S::SerializeMap>;
231    type SerializeTuple = Impossible<S::Ok, S::Error>;
232    type SerializeTupleStruct = Impossible<S::Ok, S::Error>;
233    type SerializeTupleVariant = Impossible<S::Ok, S::Error>;
234    type SerializeMap = Impossible<S::Ok, S::Error>;
235    type SerializeStruct = Impossible<S::Ok, S::Error>;
236    type SerializeStructVariant = Impossible<S::Ok, S::Error>;
237
238    fn serialize_bool(self, _v: bool) -> Result<Self::Ok, Self::Error> {
239        Err(SerError::custom("wrong type for KeyValueMap"))
240    }
241
242    fn serialize_i8(self, _v: i8) -> Result<Self::Ok, Self::Error> {
243        Err(SerError::custom("wrong type for KeyValueMap"))
244    }
245
246    fn serialize_i16(self, _v: i16) -> Result<Self::Ok, Self::Error> {
247        Err(SerError::custom("wrong type for KeyValueMap"))
248    }
249
250    fn serialize_i32(self, _v: i32) -> Result<Self::Ok, Self::Error> {
251        Err(SerError::custom("wrong type for KeyValueMap"))
252    }
253
254    fn serialize_i64(self, _v: i64) -> Result<Self::Ok, Self::Error> {
255        Err(SerError::custom("wrong type for KeyValueMap"))
256    }
257
258    fn serialize_i128(self, _v: i128) -> Result<Self::Ok, Self::Error> {
259        Err(SerError::custom("wrong type for KeyValueMap"))
260    }
261
262    fn serialize_u8(self, _v: u8) -> Result<Self::Ok, Self::Error> {
263        Err(SerError::custom("wrong type for KeyValueMap"))
264    }
265
266    fn serialize_u16(self, _v: u16) -> Result<Self::Ok, Self::Error> {
267        Err(SerError::custom("wrong type for KeyValueMap"))
268    }
269
270    fn serialize_u32(self, _v: u32) -> Result<Self::Ok, Self::Error> {
271        Err(SerError::custom("wrong type for KeyValueMap"))
272    }
273
274    fn serialize_u64(self, _v: u64) -> Result<Self::Ok, Self::Error> {
275        Err(SerError::custom("wrong type for KeyValueMap"))
276    }
277
278    fn serialize_u128(self, _v: u128) -> Result<Self::Ok, Self::Error> {
279        Err(SerError::custom("wrong type for KeyValueMap"))
280    }
281
282    fn serialize_f32(self, _v: f32) -> Result<Self::Ok, Self::Error> {
283        Err(SerError::custom("wrong type for KeyValueMap"))
284    }
285
286    fn serialize_f64(self, _v: f64) -> Result<Self::Ok, Self::Error> {
287        Err(SerError::custom("wrong type for KeyValueMap"))
288    }
289
290    fn serialize_char(self, _v: char) -> Result<Self::Ok, Self::Error> {
291        Err(SerError::custom("wrong type for KeyValueMap"))
292    }
293
294    fn serialize_str(self, _v: &str) -> Result<Self::Ok, Self::Error> {
295        Err(SerError::custom("wrong type for KeyValueMap"))
296    }
297
298    fn serialize_bytes(self, _v: &[u8]) -> Result<Self::Ok, Self::Error> {
299        Err(SerError::custom("wrong type for KeyValueMap"))
300    }
301
302    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
303        Err(SerError::custom("wrong type for KeyValueMap"))
304    }
305
306    fn serialize_some<T>(self, _value: &T) -> Result<Self::Ok, Self::Error>
307    where
308        T: Serialize + ?Sized,
309    {
310        Err(SerError::custom("wrong type for KeyValueMap"))
311    }
312
313    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
314        Err(SerError::custom("wrong type for KeyValueMap"))
315    }
316
317    fn serialize_unit_struct(self, _name: &'static str) -> Result<Self::Ok, Self::Error> {
318        Err(SerError::custom("wrong type for KeyValueMap"))
319    }
320
321    fn serialize_unit_variant(
322        self,
323        _name: &'static str,
324        _variant_index: u32,
325        _variant: &'static str,
326    ) -> Result<Self::Ok, Self::Error> {
327        Err(SerError::custom("wrong type for KeyValueMap"))
328    }
329
330    fn serialize_newtype_struct<T>(
331        self,
332        _name: &'static str,
333        _value: &T,
334    ) -> Result<Self::Ok, Self::Error>
335    where
336        T: Serialize + ?Sized,
337    {
338        Err(SerError::custom("wrong type for KeyValueMap"))
339    }
340
341    fn serialize_newtype_variant<T>(
342        self,
343        _name: &'static str,
344        _variant_index: u32,
345        _variant: &'static str,
346        _value: &T,
347    ) -> Result<Self::Ok, Self::Error>
348    where
349        T: Serialize + ?Sized,
350    {
351        Err(SerError::custom("wrong type for KeyValueMap"))
352    }
353
354    fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
355        let is_human_readable = self.0.is_human_readable();
356        self.0
357            .serialize_map(len)
358            .map(|delegate| SerializeSeqElement {
359                delegate,
360                is_human_readable,
361            })
362    }
363
364    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, Self::Error> {
365        Err(SerError::custom("wrong type for KeyValueMap"))
366    }
367
368    fn serialize_tuple_struct(
369        self,
370        _name: &'static str,
371        _len: usize,
372    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
373        Err(SerError::custom("wrong type for KeyValueMap"))
374    }
375
376    fn serialize_tuple_variant(
377        self,
378        _name: &'static str,
379        _variant_index: u32,
380        _variant: &'static str,
381        _len: usize,
382    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
383        Err(SerError::custom("wrong type for KeyValueMap"))
384    }
385
386    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
387        Err(SerError::custom("wrong type for KeyValueMap"))
388    }
389
390    fn serialize_struct(
391        self,
392        _name: &'static str,
393        _len: usize,
394    ) -> Result<Self::SerializeStruct, Self::Error> {
395        Err(SerError::custom("wrong type for KeyValueMap"))
396    }
397
398    fn serialize_struct_variant(
399        self,
400        _name: &'static str,
401        _variant_index: u32,
402        _variant: &'static str,
403        _len: usize,
404    ) -> Result<Self::SerializeStructVariant, Self::Error> {
405        Err(SerError::custom("wrong type for KeyValueMap"))
406    }
407
408    fn is_human_readable(&self) -> bool {
409        self.0.is_human_readable()
410    }
411}
412
413/// Serialize a single element but turn the sequence into a map logic.
414///
415/// It uses [`ElementAsKeyValueSerializer`] for the map element serialization.
416///
417/// The [`Serializer`] implementation handles `serialize_struct`, `serialize_map` and `serialize_seq` functions by deferring the work to [`SerializeStruct`], [`SerializeMap`] and [`SerializeSeq`] respectively.
418struct SerializeSeqElement<M> {
419    delegate: M,
420    is_human_readable: bool,
421}
422
423impl<M> SerializeSeq for SerializeSeqElement<M>
424where
425    M: SerializeMap,
426{
427    type Ok = M::Ok;
428    type Error = M::Error;
429
430    fn serialize_element<T>(&mut self, value: &T) -> Result<(), Self::Error>
431    where
432        T: Serialize + ?Sized,
433    {
434        value.serialize(ElementAsKeyValueSerializer {
435            delegate: &mut self.delegate,
436            is_human_readable: self.is_human_readable,
437        })?;
438        Ok(())
439    }
440
441    fn end(self) -> Result<Self::Ok, Self::Error> {
442        self.delegate.end()
443    }
444}
445
446struct ElementAsKeyValueSerializer<'a, M> {
447    delegate: &'a mut M,
448    is_human_readable: bool,
449}
450
451impl<'a, M> Serializer for ElementAsKeyValueSerializer<'a, M>
452where
453    M: SerializeMap,
454{
455    type Ok = ();
456    type Error = M::Error;
457
458    type SerializeSeq = KeyValueSeqSerializer<'a, M>;
459    type SerializeTuple = KeyValueTupleSerializer<'a, M>;
460    type SerializeTupleStruct = KeyValueTupleStructSerializer<'a, M>;
461    type SerializeTupleVariant = Impossible<Self::Ok, Self::Error>;
462    type SerializeMap = KeyValueMapSerializer<'a, M>;
463    type SerializeStruct = KeyValueStructSerializer<'a, M>;
464    type SerializeStructVariant = Impossible<Self::Ok, Self::Error>;
465
466    fn serialize_bool(self, _v: bool) -> Result<Self::Ok, Self::Error> {
467        Err(SerError::custom("wrong type for KeyValueMap"))
468    }
469
470    fn serialize_i8(self, _v: i8) -> Result<Self::Ok, Self::Error> {
471        Err(SerError::custom("wrong type for KeyValueMap"))
472    }
473
474    fn serialize_i16(self, _v: i16) -> Result<Self::Ok, Self::Error> {
475        Err(SerError::custom("wrong type for KeyValueMap"))
476    }
477
478    fn serialize_i32(self, _v: i32) -> Result<Self::Ok, Self::Error> {
479        Err(SerError::custom("wrong type for KeyValueMap"))
480    }
481
482    fn serialize_i64(self, _v: i64) -> Result<Self::Ok, Self::Error> {
483        Err(SerError::custom("wrong type for KeyValueMap"))
484    }
485
486    fn serialize_i128(self, _v: i128) -> Result<Self::Ok, Self::Error> {
487        Err(SerError::custom("wrong type for KeyValueMap"))
488    }
489
490    fn serialize_u8(self, _v: u8) -> Result<Self::Ok, Self::Error> {
491        Err(SerError::custom("wrong type for KeyValueMap"))
492    }
493
494    fn serialize_u16(self, _v: u16) -> Result<Self::Ok, Self::Error> {
495        Err(SerError::custom("wrong type for KeyValueMap"))
496    }
497
498    fn serialize_u32(self, _v: u32) -> Result<Self::Ok, Self::Error> {
499        Err(SerError::custom("wrong type for KeyValueMap"))
500    }
501
502    fn serialize_u64(self, _v: u64) -> Result<Self::Ok, Self::Error> {
503        Err(SerError::custom("wrong type for KeyValueMap"))
504    }
505
506    fn serialize_u128(self, _v: u128) -> Result<Self::Ok, Self::Error> {
507        Err(SerError::custom("wrong type for KeyValueMap"))
508    }
509
510    fn serialize_f32(self, _v: f32) -> Result<Self::Ok, Self::Error> {
511        Err(SerError::custom("wrong type for KeyValueMap"))
512    }
513
514    fn serialize_f64(self, _v: f64) -> Result<Self::Ok, Self::Error> {
515        Err(SerError::custom("wrong type for KeyValueMap"))
516    }
517
518    fn serialize_char(self, _v: char) -> Result<Self::Ok, Self::Error> {
519        Err(SerError::custom("wrong type for KeyValueMap"))
520    }
521
522    fn serialize_str(self, _v: &str) -> Result<Self::Ok, Self::Error> {
523        Err(SerError::custom("wrong type for KeyValueMap"))
524    }
525
526    fn serialize_bytes(self, _v: &[u8]) -> Result<Self::Ok, Self::Error> {
527        Err(SerError::custom("wrong type for KeyValueMap"))
528    }
529
530    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
531        Err(SerError::custom("wrong type for KeyValueMap"))
532    }
533
534    fn serialize_some<T>(self, _value: &T) -> Result<Self::Ok, Self::Error>
535    where
536        T: Serialize + ?Sized,
537    {
538        Err(SerError::custom("wrong type for KeyValueMap"))
539    }
540
541    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
542        Err(SerError::custom("wrong type for KeyValueMap"))
543    }
544
545    fn serialize_unit_struct(self, _name: &'static str) -> Result<Self::Ok, Self::Error> {
546        Err(SerError::custom("wrong type for KeyValueMap"))
547    }
548
549    fn serialize_unit_variant(
550        self,
551        _name: &'static str,
552        _variant_index: u32,
553        _variant: &'static str,
554    ) -> Result<Self::Ok, Self::Error> {
555        Err(SerError::custom("wrong type for KeyValueMap"))
556    }
557
558    fn serialize_newtype_struct<T>(
559        self,
560        _name: &'static str,
561        _value: &T,
562    ) -> Result<Self::Ok, Self::Error>
563    where
564        T: Serialize + ?Sized,
565    {
566        Err(SerError::custom("wrong type for KeyValueMap"))
567    }
568
569    fn serialize_newtype_variant<T>(
570        self,
571        _name: &'static str,
572        _variant_index: u32,
573        _variant: &'static str,
574        _value: &T,
575    ) -> Result<Self::Ok, Self::Error>
576    where
577        T: Serialize + ?Sized,
578    {
579        Err(SerError::custom("wrong type for KeyValueMap"))
580    }
581
582    fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
583        Ok(KeyValueSeqSerializer {
584            delegate: self.delegate,
585            is_human_readable: self.is_human_readable,
586            content: utils::vec_with_capacity_cautious(Some(len.unwrap_or(17).saturating_sub(1))),
587            key: None,
588        })
589    }
590
591    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple, Self::Error> {
592        Ok(KeyValueTupleSerializer {
593            delegate: self.delegate,
594            is_human_readable: self.is_human_readable,
595            content: utils::vec_with_capacity_cautious(Some(len.saturating_sub(1))),
596            key: None,
597        })
598    }
599
600    fn serialize_tuple_struct(
601        self,
602        name: &'static str,
603        len: usize,
604    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
605        Ok(KeyValueTupleStructSerializer {
606            delegate: self.delegate,
607            is_human_readable: self.is_human_readable,
608            name,
609            content: utils::vec_with_capacity_cautious(Some(len.saturating_sub(1))),
610            key: None,
611        })
612    }
613
614    fn serialize_tuple_variant(
615        self,
616        _name: &'static str,
617        _variant_index: u32,
618        _variant: &'static str,
619        _len: usize,
620    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
621        Err(SerError::custom("wrong type for KeyValueMap"))
622    }
623
624    fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
625        Ok(KeyValueMapSerializer {
626            delegate: self.delegate,
627            is_human_readable: self.is_human_readable,
628            content: utils::vec_with_capacity_cautious(Some(len.unwrap_or(17).saturating_sub(1))),
629            next_is_magic_key: false,
630            key: None,
631            tmp: None,
632        })
633    }
634
635    fn serialize_struct(
636        self,
637        name: &'static str,
638        len: usize,
639    ) -> Result<Self::SerializeStruct, Self::Error> {
640        Ok(KeyValueStructSerializer {
641            delegate: self.delegate,
642            is_human_readable: self.is_human_readable,
643            name,
644            content: utils::vec_with_capacity_cautious(Some(len.saturating_sub(1))),
645            key: None,
646        })
647    }
648
649    fn serialize_struct_variant(
650        self,
651        _name: &'static str,
652        _variant_index: u32,
653        _variant: &'static str,
654        _len: usize,
655    ) -> Result<Self::SerializeStructVariant, Self::Error> {
656        Err(SerError::custom("wrong type for KeyValueMap"))
657    }
658
659    fn is_human_readable(&self) -> bool {
660        self.is_human_readable
661    }
662}
663
664/// Serialize a sequence to a key and value pair of a map.
665///
666/// This requires that the sequence has at least one element.
667struct KeyValueSeqSerializer<'a, M> {
668    delegate: &'a mut M,
669    is_human_readable: bool,
670    content: Vec<SerContent>,
671    key: Option<SerContent>,
672}
673
674impl<M> SerializeSeq for KeyValueSeqSerializer<'_, M>
675where
676    M: SerializeMap,
677{
678    type Ok = ();
679    type Error = M::Error;
680
681    fn serialize_element<T>(&mut self, element: &T) -> Result<(), Self::Error>
682    where
683        T: Serialize + ?Sized,
684    {
685        let element: SerContent =
686            element.serialize(ContentSerializer::new(self.is_human_readable))?;
687        if self.key.is_none() {
688            self.key = Some(element);
689            return Ok(());
690        }
691        self.content.push(element);
692        Ok(())
693    }
694
695    fn end(self) -> Result<Self::Ok, Self::Error> {
696        if let Some(key) = self.key {
697            self.delegate
698                .serialize_entry(&key, &SerContent::Seq(self.content))
699        } else {
700            Err(SerError::custom("missing value for `$key$` field"))
701        }
702    }
703}
704
705/// Serialize a tuple to a key and value pair of a map.
706///
707/// This requires that the tuple has at least one element.
708struct KeyValueTupleSerializer<'a, M> {
709    delegate: &'a mut M,
710    is_human_readable: bool,
711    content: Vec<SerContent>,
712    key: Option<SerContent>,
713}
714
715impl<M> SerializeTuple for KeyValueTupleSerializer<'_, M>
716where
717    M: SerializeMap,
718{
719    type Ok = ();
720    type Error = M::Error;
721
722    fn serialize_element<T>(&mut self, element: &T) -> Result<(), Self::Error>
723    where
724        T: Serialize + ?Sized,
725    {
726        let element: SerContent =
727            element.serialize(ContentSerializer::new(self.is_human_readable))?;
728        if self.key.is_none() {
729            self.key = Some(element);
730            return Ok(());
731        }
732        self.content.push(element);
733        Ok(())
734    }
735
736    fn end(self) -> Result<Self::Ok, Self::Error> {
737        if let Some(key) = self.key {
738            self.delegate
739                .serialize_entry(&key, &SerContent::Tuple(self.content))
740        } else {
741            Err(SerError::custom("missing value for `$key$` field"))
742        }
743    }
744}
745
746/// Serialize a tuple struct to a key and value pair of a map.
747///
748/// This requires that the tuple struct has at least one element.
749struct KeyValueTupleStructSerializer<'a, M> {
750    delegate: &'a mut M,
751    is_human_readable: bool,
752    name: &'static str,
753    content: Vec<SerContent>,
754    key: Option<SerContent>,
755}
756
757impl<M> SerializeTupleStruct for KeyValueTupleStructSerializer<'_, M>
758where
759    M: SerializeMap,
760{
761    type Ok = ();
762    type Error = M::Error;
763
764    fn serialize_field<T>(&mut self, field: &T) -> Result<(), Self::Error>
765    where
766        T: Serialize + ?Sized,
767    {
768        let field: SerContent = field.serialize(ContentSerializer::new(self.is_human_readable))?;
769        if self.key.is_none() {
770            self.key = Some(field);
771            return Ok(());
772        }
773        self.content.push(field);
774        Ok(())
775    }
776
777    fn end(self) -> Result<Self::Ok, Self::Error> {
778        if let Some(key) = self.key {
779            self.delegate
780                .serialize_entry(&key, &SerContent::TupleStruct(self.name, self.content))
781        } else {
782            Err(SerError::custom("missing value for `$key$` field"))
783        }
784    }
785}
786
787/// Serialize a map to a key and value pair of a map.
788///
789/// This requires that the map has one element which serializes using the magic `$key$` key.
790struct KeyValueMapSerializer<'a, M> {
791    delegate: &'a mut M,
792    is_human_readable: bool,
793    content: Vec<(SerContent, SerContent)>,
794    next_is_magic_key: bool,
795    key: Option<SerContent>,
796    tmp: Option<SerContent>,
797}
798
799impl<M> SerializeMap for KeyValueMapSerializer<'_, M>
800where
801    M: SerializeMap,
802{
803    type Ok = ();
804    type Error = M::Error;
805
806    fn serialize_key<T>(&mut self, key: &T) -> Result<(), Self::Error>
807    where
808        T: Serialize + ?Sized,
809    {
810        let key: SerContent = key.serialize(ContentSerializer::new(self.is_human_readable))?;
811        if key.as_str() == Some(MAP_KEY_IDENTIFIER) {
812            self.next_is_magic_key = true;
813            return Ok(());
814        }
815        self.tmp = Some(key);
816        Ok(())
817    }
818
819    fn serialize_value<T>(&mut self, value: &T) -> Result<(), Self::Error>
820    where
821        T: Serialize + ?Sized,
822    {
823        let value: SerContent = value.serialize(ContentSerializer::new(self.is_human_readable))?;
824
825        if self.next_is_magic_key {
826            self.next_is_magic_key = false;
827            self.key = Some(value);
828            return Ok(());
829        }
830        self.content.push((
831            self.tmp
832                .take()
833                .expect("serialize_value called before serialize_key"),
834            value,
835        ));
836        Ok(())
837    }
838
839    fn end(self) -> Result<Self::Ok, Self::Error> {
840        if let Some(key) = self.key {
841            self.delegate
842                .serialize_entry(&key, &SerContent::Map(self.content))
843        } else {
844            Err(SerError::custom("missing value for `$key$` field"))
845        }
846    }
847}
848
849/// Serialize a struct to a key and value pair of a map.
850///
851/// This requires that the struct has one field named `$key$`.
852struct KeyValueStructSerializer<'a, M> {
853    delegate: &'a mut M,
854    is_human_readable: bool,
855    name: &'static str,
856    content: Vec<(&'static str, SerContent)>,
857    key: Option<SerContent>,
858}
859
860impl<M> SerializeStruct for KeyValueStructSerializer<'_, M>
861where
862    M: SerializeMap,
863{
864    type Ok = ();
865    type Error = M::Error;
866
867    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<(), Self::Error>
868    where
869        T: Serialize + ?Sized,
870    {
871        // Serialize to a Content type first
872        let value: SerContent = value.serialize(ContentSerializer::new(self.is_human_readable))?;
873
874        if key == MAP_KEY_IDENTIFIER {
875            self.key = Some(value);
876            return Ok(());
877        }
878        self.content.push((key, value));
879        Ok(())
880    }
881
882    fn end(self) -> Result<Self::Ok, Self::Error> {
883        if let Some(key) = self.key {
884            self.delegate
885                .serialize_entry(&key, &SerContent::Struct(self.name, self.content))
886        } else {
887            Err(SerError::custom("missing value for `$key$` field"))
888        }
889    }
890}
891
892// Below is deserialization code
893
894/// Deserialize the sequence of enum instances.
895///
896/// The main [`Deserializer`] implementation handles the outer sequence (e.g., `Vec`), while the [`SeqAccess`] implementation is responsible for the inner elements.
897struct SeqDeserializer<M> {
898    delegate: M,
899    is_human_readable: bool,
900}
901
902impl<'de, M> Deserializer<'de> for SeqDeserializer<M>
903where
904    M: MapAccess<'de>,
905{
906    type Error = M::Error;
907
908    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
909    where
910        V: Visitor<'de>,
911    {
912        self.deserialize_seq(visitor)
913    }
914
915    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error>
916    where
917        V: Visitor<'de>,
918    {
919        visitor.visit_seq(self)
920    }
921
922    fn is_human_readable(&self) -> bool {
923        self.is_human_readable
924    }
925
926    forward_to_deserialize_any! {
927        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
928        bytes byte_buf option unit unit_struct newtype_struct tuple
929        tuple_struct map struct enum identifier ignored_any
930    }
931}
932
933impl<'de, M> SeqAccess<'de> for SeqDeserializer<M>
934where
935    M: MapAccess<'de>,
936{
937    type Error = M::Error;
938
939    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
940    where
941        T: DeserializeSeed<'de>,
942    {
943        let key_value: Option<DeContent<'de>> = self.delegate.next_key()?;
944        if let Some(key_value) = key_value {
945            seed.deserialize(MapKeyDeserializer {
946                delegate: &mut self.delegate,
947                is_human_readable: self.is_human_readable,
948                key_value,
949            })
950            .map(Some)
951        } else {
952            Ok(None)
953        }
954    }
955
956    fn size_hint(&self) -> Option<usize> {
957        self.delegate.size_hint()
958    }
959}
960
961struct MapKeyDeserializer<'de, M> {
962    delegate: M,
963    is_human_readable: bool,
964    key_value: DeContent<'de>,
965}
966
967impl<'de, M> Deserializer<'de> for MapKeyDeserializer<'de, M>
968where
969    M: MapAccess<'de>,
970{
971    type Error = M::Error;
972
973    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
974    where
975        V: Visitor<'de>,
976    {
977        self.deserialize_map(visitor)
978    }
979
980    fn deserialize_seq<V>(mut self, visitor: V) -> Result<V::Value, Self::Error>
981    where
982        V: Visitor<'de>,
983    {
984        self.delegate.next_value_seed(KeyValueSeqDeserialize {
985            delegate: visitor,
986            first: Some(self.key_value),
987        })
988    }
989
990    fn deserialize_tuple<V>(mut self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
991    where
992        V: Visitor<'de>,
993    {
994        self.delegate.next_value_seed(KeyValueTupleDeserialize {
995            delegate: visitor,
996            len,
997            first: Some(self.key_value),
998        })
999    }
1000
1001    fn deserialize_tuple_struct<V>(
1002        mut self,
1003        name: &'static str,
1004        len: usize,
1005        visitor: V,
1006    ) -> Result<V::Value, Self::Error>
1007    where
1008        V: Visitor<'de>,
1009    {
1010        self.delegate
1011            .next_value_seed(KeyValueTupleStructDeserialize {
1012                delegate: visitor,
1013                name,
1014                len,
1015                first: Some(self.key_value),
1016            })
1017    }
1018
1019    fn deserialize_map<V>(mut self, visitor: V) -> Result<V::Value, Self::Error>
1020    where
1021        V: Visitor<'de>,
1022    {
1023        self.delegate.next_value_seed(KeyValueMapDeserialize {
1024            delegate: visitor,
1025            first: Some(self.key_value),
1026        })
1027    }
1028
1029    fn deserialize_struct<V>(
1030        mut self,
1031        name: &'static str,
1032        fields: &'static [&'static str],
1033        visitor: V,
1034    ) -> Result<V::Value, Self::Error>
1035    where
1036        V: Visitor<'de>,
1037    {
1038        self.delegate.next_value_seed(KeyValueStructDeserialize {
1039            delegate: visitor,
1040            name,
1041            fields,
1042            first: Some(self.key_value),
1043        })
1044    }
1045
1046    fn is_human_readable(&self) -> bool {
1047        self.is_human_readable
1048    }
1049
1050    forward_to_deserialize_any! {
1051        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
1052        bytes byte_buf option unit unit_struct newtype_struct
1053        enum identifier ignored_any
1054    }
1055}
1056
1057struct KeyValueSeqDeserialize<'de, V> {
1058    delegate: V,
1059    first: Option<DeContent<'de>>,
1060}
1061
1062impl<'de, V> DeserializeSeed<'de> for KeyValueSeqDeserialize<'de, V>
1063where
1064    V: Visitor<'de>,
1065{
1066    type Value = V::Value;
1067
1068    fn deserialize<D>(mut self, deserializer: D) -> Result<Self::Value, D::Error>
1069    where
1070        D: Deserializer<'de>,
1071    {
1072        let is_human_readable = deserializer.is_human_readable();
1073        deserializer.deserialize_seq(VisitorWrapper {
1074            delegate: self.delegate,
1075            is_human_readable,
1076            first: self.first.take(),
1077        })
1078    }
1079}
1080
1081struct KeyValueTupleDeserialize<'de, V> {
1082    delegate: V,
1083    len: usize,
1084    first: Option<DeContent<'de>>,
1085}
1086
1087impl<'de, V> DeserializeSeed<'de> for KeyValueTupleDeserialize<'de, V>
1088where
1089    V: Visitor<'de>,
1090{
1091    type Value = V::Value;
1092
1093    fn deserialize<D>(mut self, deserializer: D) -> Result<Self::Value, D::Error>
1094    where
1095        D: Deserializer<'de>,
1096    {
1097        let is_human_readable = deserializer.is_human_readable();
1098        deserializer.deserialize_tuple(
1099            self.len,
1100            VisitorWrapper {
1101                delegate: self.delegate,
1102                is_human_readable,
1103                first: self.first.take(),
1104            },
1105        )
1106    }
1107}
1108
1109struct KeyValueTupleStructDeserialize<'de, V> {
1110    delegate: V,
1111    name: &'static str,
1112    len: usize,
1113    first: Option<DeContent<'de>>,
1114}
1115
1116impl<'de, V> DeserializeSeed<'de> for KeyValueTupleStructDeserialize<'de, V>
1117where
1118    V: Visitor<'de>,
1119{
1120    type Value = V::Value;
1121
1122    fn deserialize<D>(mut self, deserializer: D) -> Result<Self::Value, D::Error>
1123    where
1124        D: Deserializer<'de>,
1125    {
1126        let is_human_readable = deserializer.is_human_readable();
1127        deserializer.deserialize_tuple_struct(
1128            self.name,
1129            self.len,
1130            VisitorWrapper {
1131                delegate: self.delegate,
1132                is_human_readable,
1133                first: self.first.take(),
1134            },
1135        )
1136    }
1137}
1138
1139struct KeyValueMapDeserialize<'de, V> {
1140    delegate: V,
1141    first: Option<DeContent<'de>>,
1142}
1143
1144impl<'de, V> DeserializeSeed<'de> for KeyValueMapDeserialize<'de, V>
1145where
1146    V: Visitor<'de>,
1147{
1148    type Value = V::Value;
1149
1150    fn deserialize<D>(mut self, deserializer: D) -> Result<Self::Value, D::Error>
1151    where
1152        D: Deserializer<'de>,
1153    {
1154        let is_human_readable = deserializer.is_human_readable();
1155        deserializer.deserialize_map(VisitorWrapper {
1156            delegate: self.delegate,
1157            is_human_readable,
1158            first: self.first.take(),
1159        })
1160    }
1161}
1162
1163struct KeyValueStructDeserialize<'de, V> {
1164    delegate: V,
1165    name: &'static str,
1166    fields: &'static [&'static str],
1167    first: Option<DeContent<'de>>,
1168}
1169
1170impl<'de, V> DeserializeSeed<'de> for KeyValueStructDeserialize<'de, V>
1171where
1172    V: Visitor<'de>,
1173{
1174    type Value = V::Value;
1175
1176    fn deserialize<D>(mut self, deserializer: D) -> Result<Self::Value, D::Error>
1177    where
1178        D: Deserializer<'de>,
1179    {
1180        let is_human_readable = deserializer.is_human_readable();
1181        deserializer.deserialize_struct(
1182            self.name,
1183            self.fields,
1184            VisitorWrapper {
1185                delegate: self.delegate,
1186                is_human_readable,
1187                first: self.first.take(),
1188            },
1189        )
1190    }
1191}
1192
1193struct VisitorWrapper<'de, V> {
1194    delegate: V,
1195    is_human_readable: bool,
1196    first: Option<DeContent<'de>>,
1197}
1198
1199impl<'de, V> Visitor<'de> for VisitorWrapper<'de, V>
1200where
1201    V: Visitor<'de>,
1202{
1203    type Value = V::Value;
1204
1205    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
1206        self.delegate.expecting(formatter)
1207    }
1208
1209    fn visit_seq<A>(self, seq: A) -> Result<Self::Value, A::Error>
1210    where
1211        A: SeqAccess<'de>,
1212    {
1213        self.delegate.visit_seq(SeqAccessWrapper {
1214            delegate: seq,
1215            is_human_readable: self.is_human_readable,
1216            first: self.first,
1217        })
1218    }
1219
1220    fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
1221    where
1222        A: MapAccess<'de>,
1223    {
1224        self.delegate.visit_map(MapAccessWrapper {
1225            delegate: map,
1226            is_human_readable: self.is_human_readable,
1227            first: self.first,
1228        })
1229    }
1230}
1231
1232struct MapAccessWrapper<'de, M> {
1233    delegate: M,
1234    is_human_readable: bool,
1235    first: Option<DeContent<'de>>,
1236}
1237
1238impl<'de, M> MapAccess<'de> for MapAccessWrapper<'de, M>
1239where
1240    M: MapAccess<'de>,
1241{
1242    type Error = M::Error;
1243
1244    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
1245    where
1246        K: DeserializeSeed<'de>,
1247    {
1248        if self.first.is_some() {
1249            seed.deserialize(serde_core::de::value::StringDeserializer::new(
1250                MAP_KEY_IDENTIFIER.to_string(),
1251            ))
1252            .map(Some)
1253        } else {
1254            self.delegate.next_key_seed(seed)
1255        }
1256    }
1257
1258    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
1259    where
1260        V: DeserializeSeed<'de>,
1261    {
1262        if let Some(first) = self.first.take() {
1263            seed.deserialize(ContentDeserializer::new(first, self.is_human_readable))
1264        } else {
1265            self.delegate.next_value_seed(seed)
1266        }
1267    }
1268}
1269
1270struct SeqAccessWrapper<'de, M> {
1271    delegate: M,
1272    is_human_readable: bool,
1273    first: Option<DeContent<'de>>,
1274}
1275
1276impl<'de, S> SeqAccess<'de> for SeqAccessWrapper<'de, S>
1277where
1278    S: SeqAccess<'de>,
1279{
1280    type Error = S::Error;
1281
1282    fn next_element_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
1283    where
1284        K: DeserializeSeed<'de>,
1285    {
1286        if let Some(first) = self.first.take() {
1287            seed.deserialize(ContentDeserializer::new(first, self.is_human_readable))
1288                .map(Some)
1289        } else {
1290            self.delegate.next_element_seed(seed)
1291        }
1292    }
1293}
serde_with/key_value_map.rs

serde_with/
key_value_map.rs
