Returning Vec<String> from an async function fails to compile

[FredrikNoren]

Describe the Bug

This code:

#[wasm_bindgen]
pub async fn get_strings() -> Vec<String> {
    vec!["hello".to_string(), "world".to_string()]
}

Expected Behavior

Should compile,

Actual Behavior

But gives the following compilation error:

the trait bound `wasm_bindgen::JsValue: From<Vec<std::string::String>>` is not satisfied
the following other types implement trait `From<T>`:
  <wasm_bindgen::JsValue as From<bool>>
  <wasm_bindgen::JsValue as From<isize>>
  <wasm_bindgen::JsValue as From<i8>>
  <wasm_bindgen::JsValue as From<i16>>
  <wasm_bindgen::JsValue as From<i32>>
  <wasm_bindgen::JsValue as From<i64>>
  <wasm_bindgen::JsValue as From<i128>>
  <wasm_bindgen::JsValue as From<usize>>
and 100 others
required for `Vec<std::string::String>` to implement `Into<wasm_bindgen::JsValue>`
required for `Vec<std::string::String>` to implement `IntoJsResult`

Additional Context

wasm-bindgen = "0.2"

[matthiasgeihs]

same here

[samankittani]

There is a way around this, but it is ugly. If you define a newtype for Vec:

pub struct VecString(Vec<String>);

Then you can impl From for VecString.

impl From<VecString> for JsValue {
    fn from(value: VecString) -> Self {
        serde_wasm_bindgen::to_value(&value).unwrap()
    }
}

You will need serde_wasm_bindgen.
I can't impl it for Vec directly because of Rust's orphan rule. You'll need the serde_wasm_bindgen crate. I am trying to find a more elegant solution

[samankittani]

Here is a better solution #3630
This will likely be fixed in the next release. In the meantime, I am adding this to my cargo.toml file:

[patch.crates-io]
wasm-bindgen = { git = "https://github.com/rustwasm/wasm-bindgen", rev = "88efe46" }

This will use the wasm-bindgen version that includes the commit that supports Vec for async functions

[daxpedda]

Considering #3630 has already been merged, I'm gonna go ahead and close this.
Let me know of this turns out to still not be fixed.