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Add support for #[wasm_bindgen] on async fn (#1754)

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This commit adds support to attach `#[wasm_bindgen]` on an `async fn`
which will change the return value into a `Promise` in JS. This in
theory has the exact same semantics as an `async` function in JS where
you call it with all the arguments, nothing happens and you get a
promise back, and then later the promise actually resolves.

This commit also adds a helper trait, `IntoJsResult`, to allow `async`
functions with multiple kinds of return values instead of requiring
everything to be `Result<JsValue, JsValue>`.
This commit is contained in:
Alex Crichton
2019-09-06 13:47:16 -05:00
committed by GitHub
parent 7fd6702c6d
commit 88618116ac
10 changed files with 236 additions and 18 deletions
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50
crates/macro/ui-tests/async-errors.stderr Normal file
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error[E0277]: the trait bound `std::result::Result<(), ()>: wasm_bindgen::__rt::IntoJsResult` is not satisfied
--> $DIR/async-errors.rs:29:1
|
29 | #[wasm_bindgen]
| ^^^^^^^^^^^^^^^ the trait `wasm_bindgen::__rt::IntoJsResult` is not implemented for `std::result::Result<(), ()>`
|
= help: the following implementations were found:
<std::result::Result<(), E> as wasm_bindgen::__rt::IntoJsResult>
<std::result::Result<T, E> as wasm_bindgen::__rt::IntoJsResult>
= note: required by `wasm_bindgen::__rt::IntoJsResult::into_js_result`
error[E0277]: the trait bound `std::result::Result<(), BadType>: wasm_bindgen::__rt::IntoJsResult` is not satisfied
--> $DIR/async-errors.rs:31:1
|
31 | #[wasm_bindgen]
| ^^^^^^^^^^^^^^^ the trait `wasm_bindgen::__rt::IntoJsResult` is not implemented for `std::result::Result<(), BadType>`
|
= help: the following implementations were found:
<std::result::Result<(), E> as wasm_bindgen::__rt::IntoJsResult>
<std::result::Result<T, E> as wasm_bindgen::__rt::IntoJsResult>
= note: required by `wasm_bindgen::__rt::IntoJsResult::into_js_result`
error[E0277]: the trait bound `wasm_bindgen::JsValue: std::convert::From<BadType>` is not satisfied
--> $DIR/async-errors.rs:33:1
|
33 | #[wasm_bindgen]
| ^^^^^^^^^^^^^^^ the trait `std::convert::From<BadType>` is not implemented for `wasm_bindgen::JsValue`
|
= help: the following implementations were found:
<wasm_bindgen::JsValue as std::convert::From<&'a T>>
<wasm_bindgen::JsValue as std::convert::From<&'a std::string::String>>
<wasm_bindgen::JsValue as std::convert::From<&'a str>>
<wasm_bindgen::JsValue as std::convert::From<MyType>>
and 62 others
= note: required because of the requirements on the impl of `std::convert::Into<wasm_bindgen::JsValue>` for `BadType`
= note: required because of the requirements on the impl of `wasm_bindgen::__rt::IntoJsResult` for `BadType`
= note: required by `wasm_bindgen::__rt::IntoJsResult::into_js_result`
error[E0277]: the trait bound `std::result::Result<BadType, wasm_bindgen::JsValue>: wasm_bindgen::__rt::IntoJsResult` is not satisfied
--> $DIR/async-errors.rs:35:1
|
35 | #[wasm_bindgen]
| ^^^^^^^^^^^^^^^ the trait `wasm_bindgen::__rt::IntoJsResult` is not implemented for `std::result::Result<BadType, wasm_bindgen::JsValue>`
|
= help: the following implementations were found:
<std::result::Result<(), E> as wasm_bindgen::__rt::IntoJsResult>
<std::result::Result<T, E> as wasm_bindgen::__rt::IntoJsResult>
= note: required by `wasm_bindgen::__rt::IntoJsResult::into_js_result`
For more information about this error, try `rustc --explain E0277`.