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serde-untagged
==============
[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/serde--untagged-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/serde-untagged)
[<img alt="crates.io" src="https://img.shields.io/crates/v/serde-untagged.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/serde-untagged)
[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-serde--untagged-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs" height="20">](https://docs.rs/serde-untagged)
[<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/serde-untagged/ci.yml?branch=master&style=for-the-badge" height="20">](https://github.com/dtolnay/serde-untagged/actions?query=branch%3Amaster)
This crate provides a Serde `Visitor` implementation that is useful for
deserializing untagged enums.
```toml
[dependencies]
serde-untagged = "0.1"
```
<br>
Untagged enum `Deserialize` impls look like this:
```rust
use serde::de::{Deserialize, Deserializer};
use serde_untagged::UntaggedEnumVisitor;
impl<'de> Deserialize<'de> for $MyType {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
UntaggedEnumVisitor::new()
/*
*
*/
.deserialize(deserializer)
}
}
```
Inside the `/* ... */`, we list each type that the untagged enum needs to
support deserializing from, giving a closure that turns the input into $MyType.
The following types are supported:
- bool
- i8, i16, i32, i64, i128, u8, u16, u32, u64, u128
- f32
- f64
- char
- string
- borrowed\_str
- bytes
- borrowed\_bytes
- byte\_buf
- unit
- seq
- map
### Example: string or struct
Cargo's `http.ssl-version` configuration supports deserialization from the
following two representations:
```toml
[http]
ssl-version = "tlsv1.3"
```
```toml
[http]
ssl-version.min = "tlsv1.2"
ssl-version.max = "tlsv1.3"
```
```rust
use serde::de::{Deserialize, Deserializer};
use serde_derive::Deserialize;
use serde_untagged::UntaggedEnumVisitor;
pub enum SslVersionConfig {
Single(String),
Range(SslVersionConfigRange),
}
impl<'de> Deserialize<'de> for SslVersionConfig {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
UntaggedEnumVisitor::new()
.string(|single| Ok(SslVersionConfig::Single(single.to_owned())))
.map(|map| map.deserialize().map(SslVersionConfig::Range))
.deserialize(deserializer)
}
}
#[derive(Deserialize)]
pub struct SslVersionConfigRange {
pub min: Option<String>,
pub max: Option<String>,
}
```
### Example: unit variant or bool
Cargo's LTO setting in profiles supports the 5 values `false`, `true`, `"fat"`,
`"thin"`, and `"off"`.
```toml
[profile.release]
lto = "thin"
```
```rust
use serde::de::{Deserialize, Deserializer, IntoDeserializer};
use serde_derive::Deserialize;
use serde_untagged::UntaggedEnumVisitor;
pub enum LinkTimeOptimization {
Enabled(bool),
Enum(LinkTimeOptimizationString),
}
impl<'de> Deserialize<'de> for LinkTimeOptimization {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
UntaggedEnumVisitor::new()
.bool(|b| Ok(LinkTimeOptimization::Enabled(b)))
.string(|string| {
let de = string.into_deserializer();
LinkTimeOptimizationString::deserialize(de).map(LinkTimeOptimization::Enum)
})
.deserialize(deserializer)
}
}
#[derive(Deserialize)]
#[serde(rename = "lowercase")]
pub enum LinkTimeOptimizationString {
Fat,
Thin,
Off,
}
```
Since `lto = true` means the same thing as `lto = "fat"` to Cargo, there are
really only 4 distinct options. This type could be implemented alternatively as:
```rust
use serde::de::{Deserialize, Deserializer, Unexpected};
use serde_untagged::UntaggedEnumVisitor;
pub enum LinkTimeOptimization {
ThinLocal, // false
Fat, // true or "fat"
Thin, // "thin"
Off, // "off"
}
impl<'de> Deserialize<'de> for LinkTimeOptimization {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
UntaggedEnumVisitor::new()
.bool(|b| match b {
false => Ok(LinkTimeOptimization::ThinLocal),
true => Ok(LinkTimeOptimization::Fat),
})
.string(|string| match string {
"fat" => Ok(LinkTimeOptimization::Fat),
"thin" => Ok(LinkTimeOptimization::Thin),
"off" => Ok(LinkTimeOptimization::Off),
_ => Err(serde::de::Error::invalid_value(
Unexpected::Str(string),
&r#""fat" or "thin" or "off""#,
)),
})
.deserialize(deserializer)
}
}
```
<br>
#### License
<sup>
Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
</sup>
<br>
<sub>
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
be dual licensed as above, without any additional terms or conditions.
</sub>
|
