props of type Option<T> cannot use None

[arcollector]

Problem

Hello there, I have this simple code

#[derive(Properties, PartialEq)]
pub struct Props {
    pub id_patient: Option<String>,
    pub id_report: Option<String>,
}

#[function_component(PatientsNavBar)]
pub fn patients_nav_bar(
    Props {
        id_patient,
        id_report,
    }: &Props,
) -> Html {
 html! { /* */ }
}

#[function_component(App)]
fn app() -> Html {
  html! {
     <PatientsNavBar id_patient={None} id_report={None} />
  }
}

the compiler outputs the following the error

type annotations needed
multiple `impl`s satisfying `std::option::Option<_>: IntoPropValue<std::option::Option<std::string::String>>` found in the `yew` crate:
- impl IntoPropValue<std::option::Option<std::string::String>> for std::option::Option<&'static str>;
- impl<T> IntoPropValue<T> for T

Could anybody bring me some light on this matter, how to set an optional prop ?

Environment:

• Yew version: [ master]
• Rust version: [1.81.1]
• Target [wasm32-unknown-unknown]
• Build tool [trunk]

[iemafzalhassan]

Hi 👋

can you please assign me this issue? I would like to work on it

[ryanobeirne]

@arcollector this is probably an issue with how the html!() macro parses things, but you can still use the fully annotated Option syntax: id_patient={Option::<String>::None}.

However, it may or may not be more appropriate to use one of the #[prop_or...] derive macros and simply omit the parameter:

#[derive(Properties, PartialEq)]
pub struct Props {
    #[prop_or_default] // default is empty string
    pub id_patient: String,
    #[prop_or_else(default_id_report)] // default calls function below
    pub id_report: String,
}

fn default_id_report() -> String {
    "000000".into()
}

#[function_component(PatientsNavBar)]
pub fn patients_nav_bar(
    Props {
        id_patient,
        id_report,
    }: &Props,
) -> Html {
 html! { /* */ }
}

#[function_component(App)]
fn app() -> Html {
  html! { <PatientsNavBar /> }
}

[Madoshakalaka]

None::<String> (instead of Option::<String>::None) should just work too. Although I agree @arcollector 's usage feels logical.

In short, this should compile (possible test case?):

#[derive(Properties, PartialEq)]
pub struct Props {
    pub foo: Option<String>,
}

#[function_component]
pub fn Bar(
    props: &Props,
) -> Html {
  html!{}
}

#[function_component]
fn App() -> Html {
  html! {
     <Bar foo={None}/>
  }
}

@iemafzalhassan are you still interested in investigating this?

[iemafzalhassan]

yes @Madoshakalaka

sorry i think I missed the notification before: would love to investigate and contribute.

thnkew so much 🙂