openethereum/crates/ethjson/src/maybe.rs
2021-01-14 15:30:57 +01:00

121 lines
3.1 KiB
Rust

// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.
// OpenEthereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// OpenEthereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with OpenEthereum. If not, see <http://www.gnu.org/licenses/>.
//! Deserializer of empty string values into optionals.
use serde::{
de::{Error, IntoDeserializer, Visitor},
Deserialize, Deserializer,
};
use std::{fmt, marker::PhantomData};
/// Deserializer of empty string values into optionals.
#[derive(Debug, PartialEq, Clone)]
pub enum MaybeEmpty<T> {
/// Some.
Some(T),
/// None.
None,
}
impl<'a, T> Deserialize<'a> for MaybeEmpty<T>
where
T: Deserialize<'a>,
{
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'a>,
{
deserializer.deserialize_any(MaybeEmptyVisitor::new())
}
}
struct MaybeEmptyVisitor<T> {
_phantom: PhantomData<T>,
}
impl<T> MaybeEmptyVisitor<T> {
fn new() -> Self {
MaybeEmptyVisitor {
_phantom: PhantomData,
}
}
}
impl<'a, T> Visitor<'a> for MaybeEmptyVisitor<T>
where
T: Deserialize<'a>,
{
type Value = MaybeEmpty<T>;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
write!(formatter, "an empty string or string-encoded type")
}
fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
where
E: Error,
{
self.visit_string(value.to_owned())
}
fn visit_string<E>(self, value: String) -> Result<Self::Value, E>
where
E: Error,
{
match value.is_empty() {
true => Ok(MaybeEmpty::None),
false => T::deserialize(value.into_deserializer()).map(MaybeEmpty::Some),
}
}
}
impl<T> Into<Option<T>> for MaybeEmpty<T> {
fn into(self) -> Option<T> {
match self {
MaybeEmpty::Some(s) => Some(s),
MaybeEmpty::None => None,
}
}
}
#[cfg(test)]
mod tests {
use ethereum_types;
use hash::H256;
use maybe::MaybeEmpty;
use serde_json;
use std::str::FromStr;
#[test]
fn maybe_deserialization() {
let s = r#"["", "5a39ed1020c04d4d84539975b893a4e7c53eab6c2965db8bc3468093a31bc5ae"]"#;
let deserialized: Vec<MaybeEmpty<H256>> = serde_json::from_str(s).unwrap();
assert_eq!(
deserialized,
vec![
MaybeEmpty::None,
MaybeEmpty::Some(H256(
ethereum_types::H256::from_str(
"5a39ed1020c04d4d84539975b893a4e7c53eab6c2965db8bc3468093a31bc5ae"
)
.unwrap()
))
]
);
}
}