如何用Serde将枚举序列化为字符串并减少依赖？

针对你的需求——仅用已依赖的serde实现枚举到字符串的转换、避免引入serde_json，这里有两个实用方案：

方案一：自定义Serde序列化器（复用serde派生规则） #

这个方案完全复用你已经配置的#[serde(rename_all = "kebab-case")]规则，不需要手动维护字符串映射，后续修改枚举变体或命名规则时无需额外同步代码。

首先实现一个仅处理unit枚举的极简序列化器：

use serde::{Serialize, Serializer};

struct StringSerializer;

impl Serializer for StringSerializer {
    type Ok = String;
    type Error = serde::ser::Error;
    type SerializeSeq = serde::ser::Impossible<String, Self::Error>;
    type SerializeTuple = serde::ser::Impossible<String, Self::Error>;
    type SerializeTupleStruct = serde::ser::Impossible<String, Self::Error>;
    type SerializeTupleVariant = serde::ser::Impossible<String, Self::Error>;
    type SerializeMap = serde::ser::Impossible<String, Self::Error>;
    type SerializeStruct = serde::ser::Impossible<String, Self::Error>;
    type SerializeStructVariant = serde::ser::Impossible<String, Self::Error>;

    // 核心逻辑：直接返回serde处理后的变体名称
    fn serialize_unit_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
    ) -> Result<Self::Ok, Self::Error> {
        Ok(variant.to_string())
    }

    // 其他类型直接返回错误（我们只处理unit枚举）
    fn serialize_bool(self, _v: bool) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_i8(self, _v: i8) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_i16(self, _v: i16) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_i32(self, _v: i32) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_i64(self, _v: i64) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_u8(self, _v: u8) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_u16(self, _v: u16) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_u32(self, _v: u32) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_u64(self, _v: u64) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_f32(self, _v: f32) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_f64(self, _v: f64) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_char(self, _v: char) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_str(self, _v: &str) -> Result<Self::Ok, Self::Error> {
        Ok(_v.to_string())
    }

    fn serialize_bytes(self, _v: &[u8]) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_some<T: ?Sized>(self, _value: &T) -> Result<Self::Ok, Self::Error>
    where
        T: Serialize,
    {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_unit_struct(self, _name: &'static str) -> Result<Self::Ok, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_newtype_struct<T: ?Sized>(self, _name: &'static str, _value: &T) -> Result<Self::Ok, Self::Error>
    where
        T: Serialize,
    {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_tuple_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStruct, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }

    fn serialize_struct_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        _variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStructVariant, Self::Error> {
        Err(serde::ser::Error::custom("仅支持unit枚举序列化"))
    }
}

// 封装成易用的辅助函数
pub fn enum_to_string<T: Serialize>(value: &T) -> Result<String, serde::ser::Error> {
    value.serialize(StringSerializer)
}

使用示例：

fn main() {
    let pkc_type = PublicKeyCredentialType::PublicKey;
    let s = enum_to_string(&pkc_type).unwrap();
    assert_eq!(s, "public-key");

    let unknown = PublicKeyCredentialType::Unknown;
    let s_unknown = enum_to_string(&unknown).unwrap();
    assert_eq!(s_unknown, "unknown");
}

方案二：手动实现Display trait（性能最优） #

如果你的枚举变体数量不多，且后续修改频率低，直接实现Display trait是最直接高效的方式：

use std::fmt;

impl fmt::Display for PublicKeyCredentialType {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            PublicKeyCredentialType::PublicKey => write!(f, "public-key"),
            PublicKeyCredentialType::Unknown => write!(f, "unknown"),
        }
    }
}

使用时直接调用to_string()：

let s = PublicKeyCredentialType::PublicKey.to_string();
assert_eq!(s, "public-key");

方案对比 #

内容的提问来源于stack exchange，提问作者starsoccer