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use crate::prelude::*;
/// Serialize with an added prefix on every field name and deserialize by
/// trimming away the prefix.
///
/// You can set the visibility of the generated module by prefixing the module name with a module visibility.
/// `with_prefix!(pub(crate) prefix_foo "foo_");` creates a module with `pub(crate)` visibility.
/// The visibility is optional and by default `pub(self)`, i.e., private visibility is assumed.
///
/// **Note:** Use of this macro is incompatible with applying the [`deny_unknown_fields`] attribute
/// on the container.
/// While deserializing, it will always warn about unknown fields, even though they are processed
/// by the `with_prefix` wrapper.
/// More details can be found in [this issue][issue-with_prefix-deny_unknown_fields].
///
/// # Example
///
/// The [Challonge REST API] likes to use prefixes to group related fields. In
/// simplified form, their JSON may resemble the following:
///
///
/// ```json
/// {
/// "player1_name": "name1",
/// "player1_votes": 1,
/// "player2_name": "name2",
/// "player2_votes": 2
/// }
/// ```
///
/// In Rust, we would ideally like to model this data as a pair of `Player`
/// structs, rather than repeating the fields of `Player` for each prefix.
///
/// ```rust
/// # #[allow(dead_code)]
/// struct Match {
/// player1: Player,
/// player2: Player,
/// }
///
/// # #[allow(dead_code)]
/// struct Player {
/// name: String,
/// votes: u64,
/// }
/// ```
///
/// This `with_prefix!` macro produces an adapter that adds a prefix onto field
/// names during serialization and trims away the prefix during deserialization.
/// An implementation of the Challonge API would use `with_prefix!` like this:
///
/// ```rust
/// use serde::{Deserialize, Serialize};
/// use serde_with::with_prefix;
///
/// #[derive(Serialize, Deserialize)]
/// struct Match {
/// #[serde(flatten, with = "prefix_player1")]
/// player1: Player,
/// #[serde(flatten, with = "prefix_player2")]
/// player2: Player,
/// }
///
/// #[derive(Serialize, Deserialize)]
/// struct Player {
/// name: String,
/// votes: u64,
/// }
///
/// with_prefix!(prefix_player1 "player1_");
/// // You can also set the visibility of the generated prefix module, the default is private.
/// with_prefix!(pub prefix_player2 "player2_");
/// #
/// # const EXPECTED: &str = r#"{
/// # "player1_name": "name1",
/// # "player1_votes": 1,
/// # "player2_name": "name2",
/// # "player2_votes": 2
/// # }"#;
///
/// fn main() {
/// let m = Match {
/// player1: Player {
/// name: "name1".to_owned(),
/// votes: 1,
/// },
/// player2: Player {
/// name: "name2".to_owned(),
/// votes: 2,
/// },
/// };
///
/// let j = serde_json::to_string_pretty(&m).unwrap();
/// println!("{}", j);
/// #
/// # assert_eq!(j, EXPECTED);
/// }
/// ```
///
#[macro_export]
macro_rules! with_prefix {
($module:ident $prefix:expr) => {$crate::with_prefix!(pub(self) $module $prefix);};
($vis:vis $module:ident $prefix:expr) => {
$vis mod $module {
use $crate::serde::{Deserialize, Deserializer, Serialize, Serializer};
use $crate::with_prefix::WithPrefix;
#[allow(dead_code)]
pub fn serialize<T, S>(object: &T, serializer: S) -> $crate::__private__::Result<S::Ok, S::Error>
where
T: Serialize,
S: Serializer,
{
object.serialize(WithPrefix {
delegate: serializer,
prefix: $prefix,
})
}
#[allow(dead_code)]
pub fn deserialize<'de, T, D>(deserializer: D) -> $crate::__private__::Result<T, D::Error>
where
T: Deserialize<'de>,
D: Deserializer<'de>,
{
T::deserialize(WithPrefix {
delegate: deserializer,
prefix: $prefix,
})
}
}
};
}
pub struct WithPrefix<'a, T> {
pub delegate: T,
pub prefix: &'a str,
}
impl<'a, T> Serialize for WithPrefix<'a, T>
where
T: Serialize,
{
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
self.delegate.serialize(WithPrefix {
delegate: serializer,
prefix: self.prefix,
})
}
}
impl<'a, S> Serializer for WithPrefix<'a, S>
where
S: Serializer,
{
type Ok = S::Ok;
type Error = S::Error;
type SerializeSeq = Impossible<Self::Ok, Self::Error>;
type SerializeTuple = Impossible<Self::Ok, Self::Error>;
type SerializeTupleStruct = Impossible<Self::Ok, Self::Error>;
type SerializeTupleVariant = Impossible<Self::Ok, Self::Error>;
type SerializeMap = WithPrefix<'a, S::SerializeMap>;
type SerializeStruct = WithPrefix<'a, S::SerializeMap>;
type SerializeStructVariant = Impossible<Self::Ok, Self::Error>;
fn serialize_bool(self, _v: bool) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_i8(self, _v: i8) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_i16(self, _v: i16) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_i32(self, _v: i32) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_i64(self, _v: i64) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_u8(self, _v: u8) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_u16(self, _v: u16) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_u32(self, _v: u32) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_u64(self, _v: u64) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_f32(self, _v: f32) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_f64(self, _v: f64) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_char(self, _v: char) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_str(self, v: &str) -> Result<Self::Ok, Self::Error> {
self.delegate
.collect_str(&format_args!("{}{}", self.prefix, v))
}
fn serialize_bytes(self, _v: &[u8]) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
self.delegate.serialize_none()
}
fn serialize_some<T>(self, value: &T) -> Result<Self::Ok, Self::Error>
where
T: ?Sized + Serialize,
{
self.delegate.serialize_some(&WithPrefix {
delegate: value,
prefix: self.prefix,
})
}
fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_unit_struct(self, _name: &'static str) -> Result<Self::Ok, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_unit_variant(
self,
_name: &'static str,
_variant_index: u32,
variant: &'static str,
) -> Result<Self::Ok, Self::Error> {
self.serialize_str(variant)
}
fn serialize_newtype_struct<T>(
self,
_name: &'static str,
_value: &T,
) -> Result<Self::Ok, Self::Error>
where
T: ?Sized + Serialize,
{
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_newtype_variant<T>(
self,
_name: &'static str,
_variant_index: u32,
_variant: &'static str,
_value: &T,
) -> Result<Self::Ok, Self::Error>
where
T: ?Sized + Serialize,
{
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_tuple_struct(
self,
_name: &'static str,
_len: usize,
) -> Result<Self::SerializeTupleStruct, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_tuple_variant(
self,
_name: &'static str,
_variant_index: u32,
_variant: &'static str,
_len: usize,
) -> Result<Self::SerializeTupleVariant, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
Ok(WithPrefix {
delegate: self.delegate.serialize_map(len)?,
prefix: self.prefix,
})
}
fn serialize_struct(
self,
_name: &'static str,
len: usize,
) -> Result<Self::SerializeStruct, Self::Error> {
self.serialize_map(Some(len))
}
fn serialize_struct_variant(
self,
_name: &'static str,
_variant_index: u32,
_variant: &'static str,
_len: usize,
) -> Result<Self::SerializeStructVariant, Self::Error> {
Err(SerError::custom("wrong type for with_prefix"))
}
}
impl<'a, S> SerializeMap for WithPrefix<'a, S>
where
S: SerializeMap,
{
type Ok = S::Ok;
type Error = S::Error;
fn serialize_key<T>(&mut self, key: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize,
{
self.delegate.serialize_key(&WithPrefix {
delegate: key,
prefix: self.prefix,
})
}
fn serialize_value<T>(&mut self, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize,
{
self.delegate.serialize_value(value)
}
fn serialize_entry<K, V>(&mut self, key: &K, value: &V) -> Result<(), Self::Error>
where
K: ?Sized + Serialize,
V: ?Sized + Serialize,
{
self.delegate.serialize_entry(
&WithPrefix {
delegate: key,
prefix: self.prefix,
},
value,
)
}
fn end(self) -> Result<Self::Ok, Self::Error> {
self.delegate.end()
}
}
impl<'a, S> SerializeStruct for WithPrefix<'a, S>
where
S: SerializeMap,
{
type Ok = S::Ok;
type Error = S::Error;
fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<(), Self::Error>
where
T: ?Sized + Serialize,
{
let mut prefixed_key = String::with_capacity(self.prefix.len() + key.len());
prefixed_key.push_str(self.prefix);
prefixed_key.push_str(key);
self.delegate.serialize_entry(&prefixed_key, value)
}
fn end(self) -> Result<Self::Ok, Self::Error> {
self.delegate.end()
}
}
impl<'de, 'a, T> DeserializeSeed<'de> for WithPrefix<'a, T>
where
T: DeserializeSeed<'de>,
{
type Value = T::Value;
fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
where
D: Deserializer<'de>,
{
self.delegate.deserialize(WithPrefix {
delegate: deserializer,
prefix: self.prefix,
})
}
}
impl<'de, 'a, D> Deserializer<'de> for WithPrefix<'a, D>
where
D: Deserializer<'de>,
{
type Error = D::Error;
fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
where
V: Visitor<'de>,
{
self.delegate.deserialize_map(WithPrefix {
delegate: visitor,
prefix: self.prefix,
})
}
fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error>
where
V: Visitor<'de>,
{
self.delegate.deserialize_any(WithPrefixOption {
first_key: None,
delegate: visitor,
prefix: self.prefix,
})
}
fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value, Self::Error>
where
V: Visitor<'de>,
{
self.delegate.deserialize_identifier(WithPrefix {
delegate: visitor,
prefix: self.prefix,
})
}
forward_to_deserialize_any! {
bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
bytes byte_buf unit unit_struct newtype_struct seq tuple tuple_struct
map struct enum ignored_any
}
}
impl<'de, 'a, V> Visitor<'de> for WithPrefix<'a, V>
where
V: Visitor<'de>,
{
type Value = V::Value;
fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
self.delegate.expecting(formatter)
}
fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
where
A: MapAccess<'de>,
{
self.delegate.visit_map(WithPrefix {
delegate: map,
prefix: self.prefix,
})
}
}
impl<'de, 'a, A> MapAccess<'de> for WithPrefix<'a, A>
where
A: MapAccess<'de>,
{
type Error = A::Error;
fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
where
K: DeserializeSeed<'de>,
{
while let Some(s) = self.delegate.next_key::<String>()? {
if let Some(without_prefix) = s.strip_prefix(self.prefix) {
return seed
.deserialize(without_prefix.into_deserializer())
.map(Some);
}
self.delegate.next_value::<IgnoredAny>()?;
}
Ok(None)
}
fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
where
V: DeserializeSeed<'de>,
{
self.delegate.next_value_seed(seed)
}
}
pub struct WithPrefixOption<'a, T> {
first_key: Option<String>,
delegate: T,
prefix: &'a str,
}
impl<'de, 'a, V> Visitor<'de> for WithPrefixOption<'a, V>
where
V: Visitor<'de>,
{
type Value = V::Value;
fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
self.delegate.expecting(formatter)
}
fn visit_unit<E>(self) -> Result<Self::Value, E>
where
E: DeError,
{
self.delegate.visit_none()
}
fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
where
A: MapAccess<'de>,
{
while let Some(s) = map.next_key::<String>()? {
if s.starts_with(self.prefix) {
return self.delegate.visit_some(WithPrefixOption {
first_key: Some(s),
delegate: map,
prefix: self.prefix,
});
}
map.next_value::<IgnoredAny>()?;
}
self.delegate.visit_none()
}
}
impl<'de, 'a, A> Deserializer<'de> for WithPrefixOption<'a, A>
where
A: MapAccess<'de>,
{
type Error = A::Error;
fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
where
V: Visitor<'de>,
{
visitor.visit_map(self)
}
forward_to_deserialize_any! {
bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
bytes byte_buf option unit unit_struct newtype_struct seq tuple
tuple_struct map struct enum identifier ignored_any
}
}
impl<'de, 'a, A> MapAccess<'de> for WithPrefixOption<'a, A>
where
A: MapAccess<'de>,
{
type Error = A::Error;
fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
where
K: DeserializeSeed<'de>,
{
if let Some(s) = self.first_key.take() {
let without_prefix = s[self.prefix.len()..].into_deserializer();
return seed.deserialize(without_prefix).map(Some);
}
while let Some(s) = self.delegate.next_key::<String>()? {
if let Some(without_prefix) = s.strip_prefix(self.prefix) {
return seed
.deserialize(without_prefix.into_deserializer())
.map(Some);
}
self.delegate.next_value::<IgnoredAny>()?;
}
Ok(None)
}
fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
where
V: DeserializeSeed<'de>,
{
self.delegate.next_value_seed(seed)
}
}