JSON.stringify with optional arguments

[liamcurry]

JSON.stringify has two optional arguments that are unsupported in js-sys.

• MDN docs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify
• js_sys::JSON::stringify implementation: https://github.com/rustwasm/wasm-bindgen/blob/master/crates/js-sys/src/lib.rs#L3793

The two arguments are:

1. replacer, is nullable and can be a function or an array of JsValues.
2. space, is nullable and can be a str or a number.

I imagine two new functions could be exported to support this (untested):

#[wasm_bindgen]
extern "C" {
    #[wasm_bindgen(catch, static_method_of = JSON, js_name = stringify)]
    pub fn stringify_with_replacer(obj: &JsValue, replacer: Option<&JsValue>) -> Result<JsString, JsValue>;

    #[wasm_bindgen(catch, static_method_of = JSON, js_name = stringify)]
    pub fn stringify_with_replacer_and_space(obj: &JsValue, replacer: Option<&JsValue>, space: Option<&JsValue>) -> Result<JsString, JsValue>;
}

[alexcrichton]

Sounds like great APIs to add to me!

[fitzgen]

Overall: yes we should totally add support for these optional parameters!

---

Nitpicking: Does the stringify_with_replacer variant need to take an Option<&JsValue>? presumably if you weren't using a replacer you would use normal stringify, so it seems we don't need an Option here.

[liamcurry]

Makes sense to me. I assume then stringify_with_replacer_and_space wouldn't take an Option<&JsValue> in the last argument either.

[liamcurry]

I created PR #1190 to resolve this issue. Apparently Option<&JsValue> and Option<JsValue> are both unsupported:

error[E0277]: the trait bound `&wasm_bindgen::JsValue: wasm_bindgen::convert::OptionIntoWasmAbi` is not satisfied
    --> crates\js-sys\src\lib.rs:3769:1
     |
3769 | #[wasm_bindgen]
     | ^^^^^^^^^^^^^^^ the trait `wasm_bindgen::convert::OptionIntoWasmAbi` is not implemented for `&wasm_bindgen::JsValue`
     |
     = note: required because of the requirements on the impl of `wasm_bindgen::convert::IntoWasmAbi` for `std::option::Option<&wasm_bindgen::JsValue>`

So all the arguments are &JsValue, which is fine, people can just use JsValue::NULL instead of None.