Is there a reason why TryFromJsValue takes ownership of the JsValue?

[hrxi]

The wasm-bindgen-derive crate creates impl TryFrom<&JsValue> for <type>.

Would it be possible to take &JsValue in TryFromJsValue?

[daxpedda]

wasm-bindgen-derive is not maintained by us (rustwasm and wasm-bindgen).

Apologies for the very late response!

[hrxi]

The question wasn't about wasm-bindgen-derive. It's about wasm_bindgen::convert::TryFromJsValue. Could you re-open the issue?

[daxpedda]

Ah, I see!

So TryFromJsValue is an internal API, unless we intend to use it internally in wasm-bindgen somehow, there would be no reason to change that.

What exactly are you trying to achieve?
Maybe a public API is missing for what you are trying to do?

[hrxi]

So TryFromJsValue is an internal API

I'm not sure what you mean by "internal API". It seems to be exposed: wasm_bindgen::convert::TryFromJsValue.

We considered using it, but it requires cloning to turn the &JsValue into a JsValue. With wasm-bindgen-derive, we could do the following (js_value_ref is of type &JsValue)

PublicKey::try_from(js_value_ref)

With TryFromJsValue, we need to do

PublicKey::try_from_js_value(js_value_ref.to_owned())

Could the TryFromJsValue trait be changed to take the incoming JsValue by reference instead of requiring an owned copy?

[daxpedda]

So TryFromJsValue is an internal API

I'm not sure what you mean by "internal API". It seems to be exposed: wasm_bindgen::convert::TryFromJsValue.

It says right there at the top of the module:

This is mostly an internal module, no stability guarantees are provided. Use at your own risk.

Unless you know exactly what you are doing, don't use this API.
Its meant for proc-macros and using wasm-bindgen descriptors to define how exports/imports are generated.

---

What kind of type is PublicKey?
I assume its an exported type?
You should probably take a look at JsCast.

[hrxi]

It says right there at the top of the module:

This is mostly an internal module, no stability guarantees are provided. Use at your own risk.

Thanks. That clarifies that we shouldn't use it. Thanks.

[sisou]

@hrxi To be fair, the external crate says in it's documentation that the type it is derived for must implement Clone and it uses it, too: https://docs.rs/wasm-bindgen-derive-macro/0.3.0/src/wasm_bindgen_derive_macro/lib.rs.html#171

So basically the external crate calls the .clone() for us, whereas when using the internal trait, we explicitly clone it ourselves.