英文:
How do you propagate errors in a Rust serde serializer?
问题
I'm here to help with the translation. Here's the translated code portion:
我正在尝试实现 serde 的 [serialize_with ](https://serde.rs/field-attrs.html) 属性。我有以下代码：```rustuse serde::Serializer;pub fn serialize_json_as_string<S>(json: &serde_json::value::Value, s: S) -> Result<S::Ok, S::Error>whereS: Serializer,{let string = serde_json::to_string(json).unwrap();s.serialize_str(&string)}
我不喜欢倒数第二行的 unwrap()。但我无法弄清如何将 to_string 返回的错误转换为 S::Error。
我尝试用类似以下的代码替换 let 行：
let string = serde_json::to_string(json)?;
我得到了以下错误：
error[E0277]: `?` 无法将错误转换为 `<S as serde::Serializer>::Error`--> src/model/field_type.rs:30:45|26 | pub fn serialize_json_as_string<S>(json: &serde_json::value::Value, s: S) -> Result<S::Ok, S::Error>| ----------------------- 预期是 `<S as serde::Serializer>::Error` 因为这个原因...30 | let string = serde_json::to_string(json)?;| ^ 问题号操作 (`?`) 隐式地使用 `From` 特性对错误值执行转换| 注意：为了实现 `Result<<S as serde::Serializer>::Ok, <S as serde::Serializer>::Error>`，需要执行 `FromResidual<Result<Infallible, serde_json::Error>>`help: 考虑进一步限制关联类型|28 | S: Serializer, <S as serde::Serializer>::Error: From<serde_json::Error>| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~有关此错误的更多信息，请尝试 `rustc --explain E0277`。
还尝试将整个内容替换为以下代码：
match serde_json::to_string(json) {Ok(string) => s.serialize_str(&string),Err(e) => Err(e.into()),}
类似的错误：
error[E0277]: 没有满足 `<S as serde::Serializer>::Error: From<serde_json::Error>` 的特性约束--> src/model/field_type.rs:32:25|32 | Err(e) => Err(e.into()),| ^^^^ 没有为 `<S as serde::Serializer>::Error` 实现 `From<serde_json::Error>` 的特性|= 注意：为了使 `serde_json::Error` 实现 `Into<<S as serde::Serializer>::Error>` 需要的特性约束help: 考虑进一步限制关联类型|28 | S: Serializer, <S as serde::Serializer>::Error: From<serde_json::Error>| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~有关此错误的更多信息，请尝试 `rustc --explain E0277`。
由于我不拥有 Serde，我假设我无法实现 into，因此我需要某种手动转换。我无法弄清楚它的具体实现方式。
<details><summary>英文:</summary>I'm trying to implement serde's [serialize_with ](https://serde.rs/field-attrs.html) attribute.I have this code:```rustuse serde::Serializer;pub fn serialize_json_as_string<S>(json: &serde_json::value::Value, s: S) -> Result<S::Ok, S::Error>whereS: Serializer,{let string = serde_json::to_string(json).unwrap();s.serialize_str(&string)}
I don't like the unwrap() on the second to last line. But I can't figure out how to convert the error that to_string returns into S::Error.
I've tried replacing the let line with something like:
let string = serde_json::to_string(json)?;
And I got:
error[E0277]: `?` couldn't convert the error to `<S as serde::Serializer>::Error`--> src/model/field_type.rs:30:45|26 | pub fn serialize_json_as_string<S>(json: &serde_json::value::Value, s: S) -> Result<S::Ok, S::Error>| ----------------------- expected `<S as serde::Serializer>::Error` because of this...30 | let string = serde_json::to_string(json)?;| ^ the trait `From<serde_json::Error>` is not implemented for `<S as serde::Serializer>::Error`|= note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait= note: required for `Result<<S as serde::Serializer>::Ok, <S as serde::Serializer>::Error>` to implement `FromResidual<Result<Infallible, serde_json::Error>>`help: consider further restricting the associated type|28 | S: Serializer, <S as serde::Serializer>::Error: From<serde_json::Error>| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~For more information about this error, try `rustc --explain E0277`.
And also tried replacing the whole thing with:
match serde_json::to_string(json) {Ok(string) => s.serialize_str(&string),Err(e) => Err(e.into()),}
Similar error:
error[E0277]: the trait bound `<S as serde::Serializer>::Error: From<serde_json::Error>` is not satisfied--> src/model/field_type.rs:32:25|32 | Err(e) => Err(e.into()),| ^^^^ the trait `From<serde_json::Error>` is not implemented for `<S as serde::Serializer>::Error`|= note: required for `serde_json::Error` to implement `Into<<S as serde::Serializer>::Error>`help: consider further restricting the associated type|28 | S: Serializer, <S as serde::Serializer>::Error: From<serde_json::Error>| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~For more information about this error, try `rustc --explain E0277`.
Since I don't own Serde, I assume I can't implement into, so I need some kind of manual conversion. I couldn't figure out what that would look like.
答案1
得分: 6
The error is not a serde error, but you can wrap it in a serde custom error like so:
use serde::{Serializer, ser::Error};pub fn serialize_json_as_string<S>(json: &serde_json::value::Value, s: S) -> Result<S::Ok, S::Error>whereS: Serializer,{let string = serde_json::to_string(json).map_err(S::Error::custom)?;s.serialize_str(&string)}
Note that you need to import serde::ser::Error as that's the trait where the custom function comes from.
英文:
The error is not a serde error, but you can wrap it in a serde custom error like so:
use serde::{Serializer, ser::Error};pub fn serialize_json_as_string<S>(json: &serde_json::value::Value, s: S) -> Result<S::Ok, S::Error>whereS: Serializer,{let string = serde_json::to_string(json).map_err(S::Error::custom)?;s.serialize_str(&string)}
Note that you need to import serde::ser::Error as that's the trait where the custom function comes from.
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