#[serde_as(as = X)] fails silently without the quotes

[Lehona]

When forgetting to add quotes to the type-string within the serde_as macro, the macro seems to do nothing, but won't throw an error, either. This results in the compiler complaining about the field in question not implementing De/Serialize. Example:

Works:

#[serde_as]
#[pyclass]
#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct Container {
    #[pyo3(get, set)]
    #[serde_as(as = "Vec<LocalPy<Inner>>")]
    pub inner: Vec<Py<Inner>>,
}

Fails because Py<Inner> does not implement De/Serialize:

#[serde_as]
#[pyclass]
#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct Container {
    #[pyo3(get, set)]
    #[serde_as(as = Vec<LocalPy<Inner>>)]
    pub inner: Vec<Py<Inner>>,
}

I guess you're using some kind of if-let on the structure of the macro and ignoring any incorrectly-constructed macros rather than throwing a compile-error if the macro structure does not match your expectations.

I hope you don't mind the frequent issues.

[jonasbb]

That is an issue indeed. I assumed the parsing crate (darling) would handle this. I have not found a way to get an error in this case.
I think this is the same issue as described in TedDriggs/darling#96.

I hope you don't mind the frequent issues.

Please, keep them going. I like seeing people use this crate and getting issues or comments is the only way to know with what people struggle.

[jonasbb]

This will be fixed by upgrading darling after TedDriggs/darling#113 gets merged.

Another issue I should probably warn about is adding an empty serde_as attribute on a field like

    // Warn or error on these
    #[serde_as()]
    no_modifiers: u32,
    #[serde_as]
    empty: u32,

These are not really wrong, just confusing as they will perform no change.

This only applies to fields and not to the proc-macro before structs, i.e,

#[serde_as]
#[derive(Serialize)]
struct S()