It's not possible to return `Vec<T>` if T only implements `IntoWasmAbi`

[bes]

Describe the Bug

It is not possible to return Vec<T: IntoWasmAbi>, but it is allowed to return just T.

Steps to Reproduce

Given this code

use serde::{Deserialize, Serialize};
use tsify::Tsify;
use wasm_bindgen::prelude::wasm_bindgen;

#[wasm_bindgen(js_name = TestClass)]
pub struct TestClass;

#[wasm_bindgen(js_class = TestClass)]
impl TestClass {
    #[wasm_bindgen]
    pub fn get_dummy_vec(&self) -> Vec<Dummy> {
        vec![Dummy {
            data: "abc".to_string(),
        }]
    }
}

#[derive(Tsify, Serialize, Deserialize)]
#[tsify(into_wasm_abi, from_wasm_abi)]
pub struct Dummy {
    data: String,
}

error[E0277]: the trait bound `Dummy: JsObject` is not satisfied
   --> src/test_bindgen.rs:8:1
    |
8   | #[wasm_bindgen(js_class = TestClass)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `JsObject` is not implemented for `Dummy`
    |
    = help: the following other types implement trait `JsObject`:
              Array
              ArrayBuffer
            and 71 others
    = note: required for `Dummy` to implement `WasmDescribeVector`
    = note: required for `Box<[Dummy]>` to implement `wasm_bindgen::describe::WasmDescribe`
    = note: 1 redundant requirement hidden
    = note: required for `Vec<Dummy>` to implement `wasm_bindgen::describe::WasmDescribe`
note: required by a bound in `ReturnWasmAbi`
   --> /Users/bes/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasm-bindgen-0.2.90/src/convert/traits.rs:177:26
    |
177 | pub trait ReturnWasmAbi: WasmDescribe {
    |                          ^^^^^^^^^^^^ required by this bound in `ReturnWasmAbi`
    = note: this error originates in the attribute macro `wasm_bindgen::prelude::__wasm_bindgen_class_marker` (in Nightly builds, run with -Z macro-backtrace for more info)

But, if we wrap the Vec in something that itself implements IntoWasmAbi everything works:

use serde::{Deserialize, Serialize};
use tsify::Tsify;
use wasm_bindgen::prelude::wasm_bindgen;

#[wasm_bindgen(js_name = TestClass)]
pub struct TestClass;

#[wasm_bindgen(js_class = TestClass)]
impl TestClass {
    // #[wasm_bindgen]
    // pub fn get_dummy_vec(&self) -> Vec<Dummy> {
    //     vec![Dummy {
    //         data: "abc".to_string(),
    //     }]
    // }
    //
    #[wasm_bindgen]
    pub fn get_dummy_collection(&self) -> DummyCollection {
        let dummies = vec![Dummy {
            data: "abc".to_string(),
        }];
        DummyCollection(dummies)
    }
}

#[derive(Tsify, Serialize, Deserialize)]
#[tsify(into_wasm_abi, from_wasm_abi)]
pub struct Dummy {
    data: String,
}

#[derive(Tsify, Serialize, Deserialize)]
#[tsify(from_wasm_abi, into_wasm_abi)]
pub struct DummyCollection(Vec<Dummy>);

Expected Behavior

I expect it to be possible to return Vec<T> where T: IntoWasmAbi.

Actual Behavior

It isn't possible to return Vec<T> where T: IntoWasmAbi, but it is perfectly possible to return the Vec when a wrapper type is added.

Additional Context

See also

• Allow returning Vec<T> #111
• Allow creating Vecs of and implement TryFrom<JsValue> for strings and exported Rust types #3554
• What's the idiomatic way to return a `Vec<T>` where T is `tsify(into_wasm_abi)`? #3697
• Returning Vec<T> where T: IntoWasmAbi madonoharu/tsify#49
  • I realized too late that tsify has been inactive for about 9 months. There is a maintained fork here, but unfortunately no issue tracker (yet?).

[daxpedda]

Returning a Vec requires VectorIntoWasmAbi.

FWIW the whole wasm_bindgen::convert module is unstable.

Let me know if this doesn't solve your issue!

[eneoli]

I realized too late that tsify has been inactive for about 9 months. There is a maintained fork here, but unfortunately no issue tracker (yet?).

tsify-next now implements VectorIntoWasmAbi and VectorFromWasmAbi.