server fn call fails with empty HashSet

[gitmalong]

#[server(SettingsApi, "/api")]
pub async fn settings_api(settings: Settings) -> Result<(), ServerFnError> {
    // do something
    Ok(())
}

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct Settings {
    pub currency: String,
    pub time_zone: String,
    /// Default valuation method
    pub valuation: ValuationMethod,
    /// Custom valuation methods
    pub valuations: HashSet<CustomValuationMethod>,
}

When calling settings_api from client side with a Settings struct that has a empty valuations HashSet(created via Default::default()) the call fails.

The browser sends only the following payload

year: 2021
settings[currency]: EUR
settings[time_zone]: Europe/Berlin
settings[valuation]: Fifo

As valuations is not an Option<HashSet<CustomValuationMethod>> value and it's therefore impossible to compile a program that does not set this field I consider this as a bug.

[gbj]

valuations should have the #[serde(default)] annotation added to it, and I think this will fix it. This is a quirk of serde_qs, the library we use for URL encoding form data.

[gitmalong]

Seems I was mistaken, thanks.I thought such a default annotation does not exist due to this comment: serde-rs/serde#1098 (comment)

However the serde default workaround works fine.

I found a related issue on serde_qs's side samscott89/serde_qs#78

[gbj]

For future readers, this is documented here.