Deserialize error

[dengzhq]

Bug Report

Version

0.5.15

Platform

64-bit (Windows)

Crates

the crates where use serde_html_form::from_str() method

Description

For code reuse, I wrote this code with the help of serde's flatten attr,

#[derive(Debug, serde::Deserialize)]
pub struct RightPageParam {
    pub name: String,
    pub id: u32,
    #[serde(flatten)]
    pub abstract_query_param: AbstractQueryParam,
}
#[derive(serde::Deserialize, Debug)]
pub struct AbstractQueryParam {
    current: Option<u32>,
    size: Option<u32>,
}
fn main() {
    let path_and_query: PathAndQuery = "/getPage?name=12&id=5&current=25&size=10".parse().unwrap();
    let query = path_and_query.query().unwrap();
    println!("query = {:?}", query);

    let value: RightPageParam = serde_html_form::from_str(query).map_err(FailedToDeserializeQueryString::__private_new::<RightPageParam, serde_html_form::de::Error>).unwrap();
    println!("value = {:?}", value);
}

but when I try to use it in a get method， it throws an exception

called `Result::unwrap()` on an `Err` value: FailedToDeserializeQueryString { error: Error { inner: Error("invalid type: string \"25\", expected u32") } }
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: FailedToDeserializeQueryString { error: Error { inner: Error("invalid type: string \"25\", expected u32") } }',

I checked the source code, the exception comes from

#[async_trait]
impl<T, S> FromRequestParts<S> for Query<T>
where
    T: DeserializeOwned,
    S: Send + Sync,
{
    type Rejection = QueryRejection;

    async fn from_request_parts(parts: &mut Parts, _state: &S) -> Result<Self, Self::Rejection> {
        let query = parts.uri.query().unwrap_or_default();
        let value = serde_html_form::from_str(query)
            .map_err(FailedToDeserializeQueryString::__private_new)?;
        Ok(Query(value))
    }
}

Is it a bug? or is there a better way to organize the code?

[davidpdrsn]

The code you posted doesn't call anything in axum. You don't use Query in your example.

I'm not quite sure what the problem is. Maybe something with #[serde(flatten)] in serde_html_form.

[davidpdrsn]

I see. There isn't anything we can do about it in axum though. When you look at how Query is implemented you see it just calls into serde_html_form (or serde_url_encoded)

So either it's a bug in their implementation or it requires you to annotate your field with a serde field attribute to make the parsing more flexible.

[dengzhq]

@jplatte hey，as the crate serde_html_form author,what do you think? Is it a serde problem or serde_html_form problem

[jplatte]

This is a problem of how serde(flatten) interacts with some parts of serde's overall way of working. It is unfortunately impossible to fix in either serde itself or serde_html_form without breaking other things.

[jplatte]

If you look for issues in serde containing the word flatten, you will find that there is a lot of them, all without any actual movement. The oldest one is serde-rs/serde#1183 and kind of related.

My recommendation is to avoid serde(flatten) whenever possible (it also hurts performance) .

[dengzhq]

oh i see, Thanks for all your answers