Serde: How can I deserialize CamelCased field names to snake_case

[martinlindhe]

Im using serde with serde-xml-rs to deserialize a xml document to a rust struct. It works well but I am trying to tidy up some.

A part of my xml looks like:

<TextColor>
    <R>255</R>
    <G>255</G>
    <B>255</B>
</TextColor>

which I can deseriealize using

#[derive(Deserialize, Debug)]
#[serde(deny_unknown_fields)]
pub struct TextColor {
    #[serde(rename="R")]
    r: u64,
    #[serde(rename="G")]
    g: u64,
    #[serde(rename="B")]
    b: u64,
}

However, I found the rename_all attrib and it seemed to fit my bill here:

#[derive(Deserialize, Debug)]
#[serde(deny_unknown_fields, rename_all = "snake_case")]
pub struct TextColor {
    r: u64,
    g: u64,
    b: u64,
}

But this now gives this error:
thread 'main' panicked at 'calledResult::unwrap()on anErrvalue: unknown fieldR, expected one ofr,g,b', src/libcore/result.rs:1009:5

Am I right in assuming rename_all only works when serializing data, and not deserializing?

Is there some way of automatically mapping the xml file's CamelCased names to snake_case names without specifying a rename attr on each field?

[oli-obk]

You're doing it completely correctly. serde-xml is reading the wrong table when looking at field names.

[martinlindhe]

Thanks for quick response! Do you want me to bring up this issue over in serde-xml camp too, or are you coordinating it?

[dtolnay]

@martinlindhe the equivalent of the rename attributes you showed would be rename_all = "UPPERCASE". Typically rename_all = "snake_case" would be used on enums only.

#[derive(Deserialize)]
#[serde(rename_all = "snake_case")]
enum Status {
    QualifiedSuccess, // renamed to look for "qualified_success" in the input
    AbjectFailure, // renamed to look for "abject_failure" in the input
}

[martinlindhe]

@dtolnay Alright! It seems to work correctly for me now, using PascalCase and a few rename="..." because the XML i'm working with is rather inconsistent. Thank you so much for your help.

[5hanth]

in case someone is here for deserializing camelCase response into rust structs, here it is

#[derive(Debug, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct Card {
    pub short_url: String,
    pub short_link: String,
    pub date_last_activity: DateTime<Utc>,
    pub attachments: Vec<Attachment>
}