86 lines
2.0 KiB
Rust
86 lines
2.0 KiB
Rust
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//! Deserializer of empty string values into optionals.
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use std::fmt;
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use std::marker::PhantomData;
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use serde::{Deserialize, Deserializer};
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use serde::de::{Error, Visitor, IntoDeserializer};
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/// Deserializer of empty string values into optionals.
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#[derive(Debug, PartialEq, Clone)]
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pub enum MaybeEmpty<T> {
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/// Some.
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Some(T),
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/// None.
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None,
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}
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impl<'a, T> Deserialize<'a> for MaybeEmpty<T> where T: Deserialize<'a> {
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fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
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where D: Deserializer<'a> {
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deserializer.deserialize_any(MaybeEmptyVisitor::new())
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}
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}
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struct MaybeEmptyVisitor<T> {
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_phantom: PhantomData<T>
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}
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impl<T> MaybeEmptyVisitor<T> {
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fn new() -> Self {
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MaybeEmptyVisitor {
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_phantom: PhantomData
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}
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}
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}
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impl<'a, T> Visitor<'a> for MaybeEmptyVisitor<T> where T: Deserialize<'a> {
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type Value = MaybeEmpty<T>;
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fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
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write!(formatter, "an empty string or string-encoded type")
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}
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fn visit_str<E>(self, value: &str) -> Result<Self::Value, E> where E: Error {
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self.visit_string(value.to_owned())
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}
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fn visit_string<E>(self, value: String) -> Result<Self::Value, E> where E: Error {
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match value.is_empty() {
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true => Ok(MaybeEmpty::None),
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false => {
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T::deserialize(value.into_deserializer()).map(MaybeEmpty::Some)
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}
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}
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}
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}
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impl<T> Into<Option<T>> for MaybeEmpty<T> {
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fn into(self) -> Option<T> {
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match self {
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MaybeEmpty::Some(s) => Some(s),
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MaybeEmpty::None => None
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use std::str::FromStr;
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use serde_json;
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use bigint::hash;
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use hash::H256;
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use maybe::MaybeEmpty;
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#[test]
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fn maybe_deserialization() {
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let s = r#"["", "5a39ed1020c04d4d84539975b893a4e7c53eab6c2965db8bc3468093a31bc5ae"]"#;
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let deserialized: Vec<MaybeEmpty<H256>> = serde_json::from_str(s).unwrap();
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assert_eq!(deserialized, vec![
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MaybeEmpty::None,
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MaybeEmpty::Some(H256(hash::H256::from_str("5a39ed1020c04d4d84539975b893a4e7c53eab6c2965db8bc3468093a31bc5ae").unwrap()))
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]);
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}
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}
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