implement OptionIntoWasmAbi for Option<&Closure>

[ctaggart]

Motivation

In Monico Editor, you configure the environment with callbacks. This is the TypeScript:

    export interface Environment {
        getWorkerUrl?(workerId: string, label: string): string;
    }

It is not readonly, so it is settable. It has a ?, so it may be set with undefined.

This works if i map it using an optional js_sys::Function:

#[wasm_bindgen()]
extern "C" {
    pub type Environment;
    # [ wasm_bindgen ( method , setter , js_name = getWorkerUrl ) ]
    pub fn set_get_worker_url(this: &Environment, value: Option<&Function>>);
}

In order to have it be more type safe, I want to use Closure:

#[wasm_bindgen()]
extern "C" {
    pub type Environment;
    # [ wasm_bindgen ( method , setter , js_name = getWorkerUrl ) ]
    pub fn set_get_worker_url(this: &Environment, value: Option<&Closure<dyn FnMut(String, String) -> String>>);
}

But then I get this error:

   Compiling monaco-editor-hello-world v0.1.0 (/Users/cameron/rs/ts2rs/monaco-editor-hello-world)
error[E0277]: the trait bound `&wasm_bindgen::closure::Closure<dyn std::ops::FnMut(std::string::String, std::string::String) -> std::string::String>: wasm_bindgen::convert::traits::OptionIntoWasmAbi` is not satisfied
  --> monaco-editor-hello-world/src/monaco.rs:10:51
   |
10 |     pub fn set_get_worker_url(this: &Environment, value: Option<&Closure<dyn FnMut(String, String) -> String>>);
   |                                                   ^^^^^ the trait `wasm_bindgen::convert::traits::OptionIntoWasmAbi` is not implemented for `&wasm_bindgen::closure::Closure<dyn std::ops::FnMut(std::string::String, std::string::String) -> std::string::String>`
   |
   = note: required because of the requirements on the impl of `wasm_bindgen::convert::traits::IntoWasmAbi` for `std::option::Option<&wasm_bindgen::closure::Closure<dyn std::ops::FnMut(std::string::String, std::string::String) -> std::string::String>>`

error[E0277]: the trait bound `&wasm_bindgen::closure::Closure<(dyn std::ops::FnMut(std::string::String, std::string::String) -> std::string::String + 'static)>: wasm_bindgen::convert::traits::OptionIntoWasmAbi` is not satisfied
 --> monaco-editor-hello-world/src/monaco.rs:4:1
  |
4 | #[wasm_bindgen()]
  | ^^^^^^^^^^^^^^^^^ the trait `wasm_bindgen::convert::traits::OptionIntoWasmAbi` is not implemented for `&wasm_bindgen::closure::Closure<(dyn std::ops::FnMut(std::string::String, std::string::String) -> std::string::String + 'static)>`
  |
  = note: required because of the requirements on the impl of `wasm_bindgen::convert::traits::IntoWasmAbi` for `std::option::Option<&wasm_bindgen::closure::Closure<(dyn std::ops::FnMut(std::string::String, std::string::String) -> std::string::String + 'static)>>`
  = note: this error originates in an attribute macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.
error: could not compile `monaco-editor-hello-world`.

To learn more, run the command again with --verbose.

Proposed Solution

Implement OptionIntoWasmAbi for Option<&Closure>.

[ctaggart]

Steps to reproduce:

git clone git@github.com:taggartsoftware/ts2rs.git
cd ts2rs
git checkout e5cd3367effd2fbb49bdbe258d6519eefe082a00
cd monaco-editor-hello-world
cargo build

[alexcrichton]

Seems reasonable to me to add! I think this should be a relatively simple PR to add.

[teymour-aldridge]

@alexcrichton can I try my hand at this?

[Pauan]

@teymour-aldridge Of course, we gladly accept PRs.

[teymour-aldridge]

Cool! I'll try and do this tommorow.

[ctaggart]

Same as #2767 & fixed by #2768. 🥳 Thanks @sinking-point 👏🏻 .