Setting a default for Duration type in proc macros

[dnaka91]

When deriving a uniffi::Record I have a few fields of type Duration and was hoping to give them a default value. However it seems at the moment the proc macros don't accept literals for it, despite durations being somewhat primitive types from the Built-in types table.

It would be great if the proc macros can be extended to accept expressions for Duration.

I only use Uniffi for Kotlin code, where there should be equivalents to construct the default value in a data class but I'm not sure if this is possible in other languages as well.

For Duration I'd imagine accepting the const constructors:

• Duration::from_secs
• Duration::from_millis
• Duration::from_micros

And eventually:

• Duration::from_secs_f32
• Duration::from_secs_f64

For example:

#[uniffi::Record]
struct Config {
    #[uniffi(default = Duration::from_secs(5))]
    max_wait: Duration,
}

[mhammond]

The defaults are needed by the bindings and currently need to conform to

uniffi-rs/uniffi_meta/src/lib.rs

Line 258 in b46ab54

pub enum LiteralMetadata {

. tbh though, I think we should consider deprecating these types in favour of custom types - I'm not sure what the default support is for them though

[dnaka91]

Thanks, then I'll better not try to implement support for a default value for those.

IIRC there is currently no support for default values when using custom types. But it's really just a nice to have for me, and I can live with this not having a default value.